[libpng16] Imported from libpng-1.6.31beta04.tar

[libpng16] Removed one of the GCC-7.1.0 'strict-overflow' warnings that
result when integers appear on both sides of a compare. Worked around the others by forcing the strict-overflow setting in the relevant functions to a level where they are not reported. Changed "FALL THROUGH" comments to "FALLTHROUGH" because GCC doesn't like the space. Worked around some C-style casts from (void*) because g++ 5.4.0 objects to them. Increased the buffer size for 'sprint' to pass the gcc 7.1.0 'sprint overflow' check that is on by default with -Wall -Wextra.
2025-07-10 18:04:09 +02:00 · 2017-07-11 12:29:53 -05:00 · 2017-07-11 08:47:05 -05:00 · 2017-07-09 19:35:10 -05:00 · 2017-07-09 17:23:56 -05:00 · 2017-07-09 16:31:45 -05:00
51 changed files with 843 additions and 256 deletions
--- a/66
+++ b/66
@@ -1,6 +1,6 @@
-Libpng 1.6.30beta03 - May 22, 2017
+Libpng 1.6.31beta04 - July 11, 2017

-This is not intended to be a public release.  It will be replaced
+This is not intended to be a public release. It will be replaced
 within a few weeks by a public version or by another test version.

 Files available for download:
@@ -8,41 +8,55 @@ Files available for download:
 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script

-   1.6.30beta03.tar.xz (LZMA-compressed, recommended)
-   1.6.30beta03.tar.gz
+   1.6.31beta04.tar.xz (LZMA-compressed, recommended)
+   1.6.31beta04.tar.gz

 Source files with CRLF line endings (for Windows), without the
 "configure" script

-   lp1630b03.7z  (LZMA-compressed, recommended)
-   lp1630b03.zip
+   lp1631b04.7z  (LZMA-compressed, recommended)
+   lp1631b04.zip

 Other information:

-   1.6.30beta03-README.txt
-   1.6.30beta03-LICENSE.txt
-   libpng-1.6.30beta03-*.asc (armored detached GPG signatures)
+   1.6.31beta04-README.txt
+   1.6.31beta04-LICENSE.txt
+   libpng-1.6.31beta04-*.asc (armored detached GPG signatures)

-Changes since the last public release (1.6.29):
+Changes since the last public release (1.6.30):

-Version 1.6.30beta01 [April 1, 2017]
-  Added missing "$(CPPFLAGS)" to the compile line for c.pic.o in
-    makefile.linux and makefile.solaris-x86 (Cosmin).
-  Revised documentation of png_get_error_ptr() in the libpng manual.
-  Silence clang -Wcomma and const drop warnings (Viktor Szakats).
-  Update Sourceforge URLs in documentation (https instead of http).
+Version 1.6.31beta01 [July 5, 2017]
+  Guard the definition of _POSIX_SOURCE in pngpriv.h (AIX already defines it;
+    bug report by Michael Felt).
+  Revised pngpriv.h to work around failure to compile arm/filter_neon.S
+    ("typedef" directive is unrecognized by the assembler). The problem
+    was introduced in libpng-1.6.30beta01.
+  Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).
+  Added special case for FreeBSD in arm/filter_neon.S (Maya Rashish).

-Version 1.6.30beta02 [April 22, 2017]
-  Document need to check for integer overflow when allocating a pixel
-    buffer for multiple rows in contrib/gregbook, contrib/pngminus,
-    example.c, and in the manual (suggested by Jaeseung Choi).
-  Removed reference to the obsolete PNG_SAFE_LIMITS macro in the documentation.
+Version 1.6.31beta02 [July 8, 2017]
+  Added instructions for disabling hardware optimizations in INSTALL.
+  Added "--enable-hardware-optimizations" configuration flag to enable
+    or disable all hardware optimizations with one flag.

-Version 1.6.30beta03 [May 22, 2017]
-  Check for integer overflow in contrib/visupng and contrib/tools/genpng.
-  Do not double evaluate CMAKE_SYSTEM_PROCESSOR in CMakeLists.txt.
-  Test CMAKE_HOST_WIN32 instead of WIN32 in CMakeLists.txt.
-  Fix some URL in documentation.
+Version 1.6.31beta03 [July 9, 2017]
+  Updated CMakeLists.txt to add INTEL_SSE and MIPS_MSA platforms.
+  Changed "int" to "png_size_t" in intel/filter_sse2.c to prevent
+    possible integer overflow (Bug report by John Bowler).
+  Quieted "declaration after statement" warnings in intel/filter_sse2.c.
+  Added scripts/makefile-linux-opt, which has hardware optimizations enabled.
+
+Version 1.6.31beta04 [July 11, 2017]
+  Removed one of the GCC-7.1.0 'strict-overflow' warnings that result when
+    integers appear on both sides of a compare.  Worked around the others by
+    forcing the strict-overflow setting in the relevant functions to a level
+    where they are not reported (John Bowler).
+  Changed "FALL THROUGH" comments to "FALLTHROUGH" because GCC doesn't like
+    the space.
+  Worked around some C-style casts from (void*) because g++ 5.4.0 objects
+    to them.
+  Increased the buffer size for 'sprint' to pass the gcc 7.1.0 'sprint
+    overflow' check that is on by default with -Wall -Wextra.

 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
--- a/51
+++ b/51
@@ -5830,7 +5830,8 @@ Version 1.6.30beta01 [April 1, 2017]
 Version 1.6.30beta02 [April 22, 2017]
  Document need to check for integer overflow when allocating a pixel
    buffer for multiple rows in contrib/gregbook, contrib/pngminus,
-    example.c, and in the manual (suggested by Jaeseung Choi).
+    example.c, and in the manual (suggested by Jaeseung Choi). This
+    is similar to the bug reported against pngquant in CVE-2016-5735.
  Removed reference to the obsolete PNG_SAFE_LIMITS macro in the documentation.

 Version 1.6.30beta03 [May 22, 2017]
@@ -5839,6 +5840,54 @@ Version 1.6.30beta03 [May 22, 2017]
  Test CMAKE_HOST_WIN32 instead of WIN32 in CMakeLists.txt.
  Fix some URL in documentation.

+Version 1.6.30beta04 [June 7, 2017]
+  Avoid writing an empty IDAT when the last IDAT exactly fills the
+    compression buffer (bug report by Brian Baird). This bug was
+    introduced in libpng-1.6.0.
+
+Version 1.6.30rc01 [June 14, 2017]
+  No changes.
+
+Version 1.6.30rc02 [June 25, 2017]
+  Update copyright year in pnglibconf.h, make ltmain.sh executable.
+  Add a reference to the libpng.download site in README.
+
+Version 1.6.30 [June 28, 2017]
+  No changes.
+
+Version 1.6.31beta01 [July 5, 2017]
+  Guard the definition of _POSIX_SOURCE in pngpriv.h (AIX already defines it;
+    bug report by Michael Felt).
+  Revised pngpriv.h to work around failure to compile arm/filter_neon.S
+    ("typedef" directive is unrecognized by the assembler). The problem
+    was introduced in libpng-1.6.30beta01.
+  Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).
+  Added special case for FreeBSD in arm/filter_neon.S (Maya Rashish).
+
+Version 1.6.31beta02 [July 8, 2017]
+  Added instructions for disabling hardware optimizations in INSTALL.
+  Added "--enable-hardware-optimizations" configuration flag to enable
+    or disable all hardware optimizations with one flag.
+
+Version 1.6.31beta03 [July 9, 2017]
+  Updated CMakeLists.txt to add INTEL_SSE and MIPS_MSA platforms.
+  Changed "int" to "png_size_t" in intel/filter_sse2.c to prevent
+    possible integer overflow (Bug report by John Bowler).
+  Quieted "declaration after statement" warnings in intel/filter_sse2.c.
+  Added scripts/makefile-linux-opt, which has hardware optimizations enabled.
+
+Version 1.6.31beta04 [July 11, 2017]
+  Removed one of the GCC-7.1.0 'strict-overflow' warnings that result when
+    integers appear on both sides of a compare.  Worked around the others by
+    forcing the strict-overflow setting in the relevant functions to a level
+    where they are not reported (John Bowler).
+  Changed "FALL THROUGH" comments to "FALLTHROUGH" because GCC doesn't like
+    the space.
+  Worked around some C-style casts from (void*) because g++ 5.4.0 objects
+    to them.
+  Increased the buffer size for 'sprint' to pass the gcc 7.1.0 'sprint
+    overflow' check that is on by default with -Wall -Wextra.
+
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 # CMakeLists.txt

-# Copyright (C) 2007,2009-2016 Glenn Randers-Pehrson
+# Copyright (C) 2007,2009-2017 Glenn Randers-Pehrson
 # Written by Christian Ehrlicher, 2007
 # Revised by Roger Lowman, 2009-2010
 # Revised by Clifford Yapp, 2011-2012
@@ -36,7 +36,7 @@ enable_testing()

 set(PNGLIB_MAJOR 1)
 set(PNGLIB_MINOR 6)
-set(PNGLIB_RELEASE 30)
+set(PNGLIB_RELEASE 31)
 set(PNGLIB_NAME libpng${PNGLIB_MAJOR}${PNGLIB_MINOR})
 set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_RELEASE})

@@ -76,9 +76,13 @@ option(PNG_FRAMEWORK "Build OS X framework" OFF)
 option(PNG_DEBUG     "Build with debug output" OFF)
 option(PNGARG        "Disable ANSI-C prototypes" OFF)

+option(PNG_HARDWARE_OPTIMIZATIONS "Enable Hardware Optimizations" ON)
+
+
 set(PNG_PREFIX "" CACHE STRING "Prefix to add to the API function names")
 set(DFA_XTRA "" CACHE FILEPATH "File containing extra configuration settings")

+if(PNG_HARDWARE_OPTIMIZATIONS)
 # set definitions and sources for arm
 if(CMAKE_SYSTEM_PROCESSOR MATCHES "^arm" OR
  CMAKE_SYSTEM_PROCESSOR MATCHES "^aarch64")
@@ -112,11 +116,9 @@ endif()
 # set definitions and sources for powerpc
 if(CMAKE_SYSTEM_PROCESSOR MATCHES "^powerpc*" OR
 	CMAKE_SYSTEM_PROCESSOR MATCHES "^ppc64*" )
-  set(PNG_POWERPC_VSX_POSSIBLE_VALUES check on off)
-  set(PNG_POWERPC_VSX "check" CACHE STRING "Enable POWERPC VSX optimizations:
-     check: (default) use internal checking code;
-     off: disable the optimizations;
-     on: turn on unconditionally.")
+  set(PNG_POWERPC_VSX_POSSIBLE_VALUES on off)
+  set(PNG_POWERPC_VSX "on" CACHE STRING "Enable POWERPC VSX optimizations:
+     off: disable the optimizations.")
  set_property(CACHE PNG_POWERPC_VSX PROPERTY STRINGS
     ${PNG_POWERPC_VSX_POSSIBLE_VALUES})
  list(FIND PNG_POWERPC_VSX_POSSIBLE_VALUES ${PNG_POWERPC_VSX} index)
@@ -127,19 +129,62 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "^powerpc*" OR
    set(libpng_powerpc_sources
      powerpc/powerpc_init.c
      powerpc/filter_vsx_intrinsics.c)
-
    if(${PNG_POWERPC_VSX} STREQUAL "on")
      add_definitions(-DPNG_POWERPC_VSX_OPT=2)
-    elseif(${PNG_POWERPC_VSX} STREQUAL "check")
-      add_definitions(-DPNG_POWERPC_VSX_CHECK_SUPPORTED)
-      message(WARNING
-      "[PNG_POWERPC_VSX==check] Please check contrib/powerpc/README file for the list of supported OSes.")
    endif()
  else()
    add_definitions(-DPNG_POWERPC_VSX_OPT=0)
  endif()
 endif()

+# set definitions and sources for intel
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "^i?86" OR
+	CMAKE_SYSTEM_PROCESSOR MATCHES "^x86_64*" )
+  set(PNG_INTEL_SSE_POSSIBLE_VALUES on off)
+  set(PNG_INTEL_SSE "on" CACHE STRING "Enable INTEL_SSE optimizations:
+     off: disable the optimizations")
+  set_property(CACHE PNG_INTEL_SSE PROPERTY STRINGS
+     ${PNG_INTEL_SSE_POSSIBLE_VALUES})
+  list(FIND PNG_INTEL_SSE_POSSIBLE_VALUES ${PNG_INTEL_SSE} index)
+  if(index EQUAL -1)
+    message(FATAL_ERROR
+      " PNG_INTEL_SSE must be one of [${PNG_INTEL_SSE_POSSIBLE_VALUES}]")
+  elseif(NOT ${PNG_INTEL_SSE} STREQUAL "no")
+    set(libpng_intel_sources
+      intel/intel_init.c
+      intel/filter_sse2_intrinsics.c)
+    if(${PNG_INTEL_SSE} STREQUAL "on")
+      add_definitions(-DPNG_INTEL_SSE_OPT=1)
+    endif()
+  else()
+    add_definitions(-DPNG_INTEL_SSE_OPT=0)
+  endif()
+endif()
+
+# set definitions and sources for MIPS
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "mipsel*" OR
+	CMAKE_SYSTEM_PROCESSOR MATCHES "mips64el*" )
+  set(PNG_MIPS_MSA_POSSIBLE_VALUES on off)
+  set(PNG_MIPS_MSA "on" CACHE STRING "Enable MIPS_MSA optimizations:
+     off: disable the optimizations")
+  set_property(CACHE PNG_MIPS_MSA PROPERTY STRINGS
+     ${PNG_MIPS_MSA_POSSIBLE_VALUES})
+  list(FIND PNG_MIPS_MSA_POSSIBLE_VALUES ${PNG_MIPS_MSA} index)
+  if(index EQUAL -1)
+    message(FATAL_ERROR
+      " PNG_MIPS_MSA must be one of [${PNG_MIPS_MSA_POSSIBLE_VALUES}]")
+  elseif(NOT ${PNG_MIPS_MSA} STREQUAL "no")
+    set(libpng_mips_sources
+      mips/mips_init.c
+      mips/filter_msa_intrinsics.c)
+    if(${PNG_MIPS_MSA} STREQUAL "on")
+      add_definitions(-DPNG_MIPS_MSA_OPT=2)
+    endif()
+  else()
+    add_definitions(-DPNG_MIPS_MSA_OPT=0)
+  endif()
+endif()
+endif(PNG_HARDWARE_OPTIMIZATIONS)

 # SET LIBNAME
 set(PNG_LIB_NAME png${PNGLIB_MAJOR}${PNGLIB_MINOR})
@@ -432,6 +477,8 @@ set(libpng_sources
  pngwtran.c
  pngwutil.c
  ${libpng_arm_sources}
+  ${libpng_intel_sources}
+  ${libpng_mips_sources}
  ${libpng_powerpc_sources}
 )
 set(pngtest_sources
@@ -726,12 +773,12 @@ macro(CREATE_SYMLINK SRC_FILE DEST_FILE)
        DEPENDS ${PNG_LIB_TARGETS}
        )
    ADD_CUSTOM_TARGET(${DEST_FILE}_COPY ALL DEPENDS ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${DEST_FILE})
-  else(WIN32 AND NOT CYGWIN AND NOT MSYS)
+  else(CMAKE_HOST_WIN32 AND NOT CYGWIN AND NOT MSYS)
    get_filename_component(LINK_TARGET "${SRC_FILE}" NAME)
    execute_process(COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_LIBRARY_OUTPUT_DIRECTORY})
    execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink "${LINK_TARGET}" ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${DEST_FILE} WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
    execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink "${LINK_TARGET}" ${DEST_FILE} WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
-  endif(WIN32 AND NOT CYGWIN AND NOT MSYS)
+  endif(CMAKE_HOST_WIN32 AND NOT CYGWIN AND NOT MSYS)
 endmacro()

 # Create source generation scripts.
@@ -770,7 +817,7 @@ endif(NOT WIN32 OR CYGWIN OR MINGW)
 # SET UP LINKS
 if(PNG_SHARED)
  set_target_properties(png PROPERTIES
-#   VERSION 16.${PNGLIB_RELEASE}.1.6.30beta03
+#   VERSION 16.${PNGLIB_RELEASE}.1.6.31beta04
    VERSION 16.${PNGLIB_RELEASE}.0
    SOVERSION 16
    CLEAN_DIRECT_OUTPUT 1)
@@ -855,7 +902,7 @@ if(NOT SKIP_INSTALL_FILES AND NOT SKIP_INSTALL_ALL )
            DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
    install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config
            DESTINATION bin)
-  endif(NOT WIN32 OR CYGWIN OR MINGW)
+  endif(NOT CMAKE_HOST_WIN32 OR CYGWIN OR MINGW)
 endif()

 # On versions of CMake that support it, create an export file CMake
--- a/71
+++ b/71
@@ -16,10 +16,11 @@ Contents
      XI. Prepending a prefix to exported symbols
     XII. Configuring for compiler xxx:
    XIII. Removing unwanted object code
-     XIV. Changes to the build and configuration of libpng in libpng-1.5.x
-      XV. Setjmp/longjmp issues
-     XVI. Common linking failures
-    XVII. Other sources of information about libpng
+     XIV. Enabling or disabling hardware optimizations
+      XV. Changes to the build and configuration of libpng in libpng-1.5.x
+     XVI. Setjmp/longjmp issues
+    XVII. Common linking failures
+   XVIII. Other sources of information about libpng

 I. Simple installation

@@ -78,8 +79,8 @@ Or you can use one of the "projects" in the "projects" directory.

 Before installing libpng, you must first install zlib, if it
 is not already on your system.  zlib can usually be found
-wherever you got libpng; otherwise go to http://zlib.net.  You can place
-zlib in the same directory as libpng or in another directory.
+wherever you got libpng; otherwise go to https://zlib.net/.  You can
+place zlib in the same directory as libpng or in another directory.

 If your system already has a preinstalled zlib you will still need
 to have access to the zlib.h and zconf.h include files that
@@ -281,7 +282,57 @@ library to fail if they call functions not available in your library.
 The size of the library itself should not be an issue, because only
 those sections that are actually used will be loaded into memory.

-XIV. Changes to the build and configuration of libpng in libpng-1.5.x
+XIV. Enabling or disabling hardware optimizations
+
+Certain hardware capabilites, such as the Intel SSE instructions,
+are normally detected at run time. Enable them with configure options
+such as one of
+
+   --enable-arm-neon=yes
+   --enable-mips-msa=yes
+   --enable-intel-sse=yes
+   --enable-powerpc-vsx=yes
+
+or enable them all at once with
+
+   --enable-hardware-optimizations=yes
+
+or, if you are not using "configure", you can use one
+or more of
+
+   CPPFLAGS += "-DPNG_ARM_NEON"
+   CPPFLAGS += "-DPNG_MIPS_MSA"
+   CPPFLAGS += "-DPNG_INTEL_SSE"
+   CPPFLAGS += "-DPNG_POWERPC_VSX"
+
+See for example scripts/makefile.linux-opt
+
+If you wish to avoid using them,
+you can disable them via the configure option
+
+   --disable-hardware-optimizations
+
+to disable them all, or
+
+   --enable-intel-sse=no
+
+to disable a particular one,
+or via compiler-command options such as
+
+   CPPFLAGS += "-DPNG_ARM_NEON_OPT=0, -DPNG_MIPS_MSA_OPT=0,
+   -DPNG_INTEL_SSE_OPT=0, -DPNG_POWERPC_VSX_OPT=0"
+
+If you are using cmake, hardware optimizations are "on"
+by default. To disable them, use
+
+    cmake . -DPNG_ARM_NEON=no -DPNG_INTEL_SSE=no \
+            -DPNG_MIPS_MSA=no -DPNG_POWERPC_VSX=no
+
+or disable them all at once with
+
+    cmake . -DPNG_HARDWARE_OPTIMIZATIONS=no
+
+XV. Changes to the build and configuration of libpng in libpng-1.5.x

 Details of internal changes to the library code can be found in the CHANGES
 file and in the GIT repository logs.  These will be of no concern to the vast
@@ -372,7 +423,7 @@ $PREFIX/include directory).  Do not edit pnglibconf.h after you have built
 libpng, because than the settings would not accurately reflect the settings
 that were used to build libpng.

-XV. Setjmp/longjmp issues
+XVI. Setjmp/longjmp issues

 Libpng uses setjmp()/longjmp() for error handling.  Unfortunately setjmp()
 is known to be not thread-safe on some platforms and we don't know of
@@ -390,7 +441,7 @@ This requires setjmp/longjmp, so you must either build the library
 with PNG_SETJMP_SUPPORTED defined, or with PNG_SIMPLIFIED_READ_SUPPORTED
 and PNG_SIMPLIFIED_WRITE_SUPPORTED undefined.

-XVI. Common linking failures
+XVII. Common linking failures

 If your application fails to find libpng or zlib entries while linking:

@@ -402,7 +453,7 @@ If your application fails to find libpng or zlib entries while linking:
  If you are using the vstudio project, observe the WARNING in
  project/vstudio/README.txt.

-XVII. Other sources of information about libpng:
+XVIII. Other sources of information about libpng:

 Further information can be found in the README and libpng-manual.txt
 files, in the individual makefiles, in png.h, and the manual pages
--- a/4
+++ b/4
@@ -10,7 +10,7 @@ this sentence.

 This code is released under the libpng license.

-libpng versions 1.0.7, July 1, 2000 through 1.6.30beta03, May 22, 2017 are
+libpng versions 1.0.7, July 1, 2000 through 1.6.31beta04, July 11, 2017 are
 Copyright (c) 2000-2002, 2004, 2006-2017 Glenn Randers-Pehrson, are
 derived from libpng-1.0.6, and are distributed according to the same
 disclaimer and license as libpng-1.0.6 with the following individuals
@@ -130,4 +130,4 @@ any encryption software.  See the EAR, paragraphs 734.3(b)(3) and

 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-May 22, 2017
+April 1, 2017
--- a/6
+++ b/6
@@ -1,4 +1,4 @@
-README for libpng version 1.6.30beta03 - May 22, 2017 (shared library 16.0)
+README for libpng version 1.6.31beta04 - July 11, 2017 (shared library 16.0)
 See the note about version numbers near the top of png.h

 See INSTALL for instructions on how to install libpng.
@@ -23,7 +23,7 @@ earlier versions if you are using a shared library.  The type of the
 png_uint_32, which will affect shared-library applications that use
 this function.

-To avoid problems with changes to the internals of png info_struct,
+To avoid problems with changes to the internals of the png info_struct,
 new APIs have been made available in 0.95 to avoid direct application
 access to info_ptr.  These functions are the png_set_<chunk> and
 png_get_<chunk> functions.  These functions should be used when
@@ -91,7 +91,7 @@ as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find
 these at http://www.libpng.org/pub/png/pngdocs.html .

 This code is currently being archived at libpng.sourceforge.io in the
-[DOWNLOAD] area, and at ftp://ftp-osl.osuosl.org/pub/libpng/src .  If you
+[DOWNLOAD] area, and at http://libpng.download/src .  If you
 can't find it in any of those places, e-mail me, and I'll help you find it.

 I am not a lawyer, but I believe that the Export Control Classification
--- a/arm/filter_neon.S
+++ b/arm/filter_neon.S
@@ -1,9 +1,9 @@

 /* filter_neon.S - NEON optimised filter functions
 *
- * Copyright (c) 2014 Glenn Randers-Pehrson
+ * Copyright (c) 2014,2017 Glenn Randers-Pehrson
 * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.6.16 [December 22, 2014]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -16,7 +16,7 @@
 #define PNG_VERSION_INFO_ONLY
 #include "../pngpriv.h"

-#if defined(__linux__) && defined(__ELF__)
+#if (defined(__linux__) || defined(__FreeBSD__)) && defined(__ELF__)
 .section .note.GNU-stack,"",%progbits /* mark stack as non-executable */
 #endif

--- a/configure.ac
+++ b/configure.ac
@@ -25,7 +25,7 @@ AC_PREREQ([2.68])

 dnl Version number stuff here:

-AC_INIT([libpng],[1.6.30beta03],[png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng],[1.6.31beta04],[png-mng-implement@lists.sourceforge.net])
 AC_CONFIG_MACRO_DIR([scripts])

 # libpng does not follow GNU file name conventions (hence 'foreign')
@@ -46,10 +46,10 @@ dnl automake, so the following is not necessary (and is not defined anyway):
 dnl AM_PREREQ([1.11.2])
 dnl stop configure from automagically running automake

-PNGLIB_VERSION=1.6.30beta03
+PNGLIB_VERSION=1.6.31beta04
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=6
-PNGLIB_RELEASE=28
+PNGLIB_RELEASE=31

 dnl End of version number stuff

@@ -300,6 +300,55 @@ AM_CONDITIONAL([DO_INSTALL_LIBPNG_CONFIG],
 # HOST SPECIFIC OPTIONS
 # =====================
 #
+# DEFAULT
+# =======
+#
+AC_ARG_ENABLE([hardware-optimizations],
+   AS_HELP_STRING([[[--enable-hardware-optimizations]]],
+      [Enable hardware optimizations: =no/off, yes/on:]),
+   [case "$enableval" in
+      no|off)
+         # disable hardware optimization on all systems:
+         enable_arm_neon=no
+         AC_DEFINE([PNG_ARM_NEON_OPT], [0],
+           [Disable ARM_NEON optimizations])
+         enable_mips_msa=no
+         AC_DEFINE([PNG_MIPS_MSA_OPT], [0],
+           [Disable MIPS_MSA optimizations])
+         enable_powerpc_vsx=no
+         AC_DEFINE([PNG_POWERPC_VSX_OPT], [0],
+           [Disable POWERPC VSX optimizations])
+         enable_intel_sse=no
+         AC_DEFINE([PNG_INTEL_SSE_OPT], [0],
+           [Disable INTEL_SSE optimizations])
+         ;;
+      *)
+         # allow enabling hardware optimization on any system:
+         case "$host_cpu" in
+            arm*|aarch64*)
+              enable_arm_neon=yes
+              AC_DEFINE([PNG_ARM_NEON_OPT], [0],
+                [Enable ARM_NEON optimizations])
+              ;;
+            mipsel*|mips64el*)
+              enable_mips_msa=yes
+              AC_DEFINE([PNG_MIPS_MSA_OPT], [0],
+                [Enable MIPS_MSA optimizations])
+              ;;
+            i?86|x86_64)
+              enable_intel_sse=yes
+              AC_DEFINE([PNG_INTEL_SSE_OPT], [1],
+                [Enable Intel SSE optimizations])
+              ;;
+            powerpc*|ppc64*)
+              enable_powerpc_vsx=yes
+              AC_DEFINE([PNG_POWERPC_VSX_OPT], [2],
+                [Enable POWERPC VSX optimizations])
+              ;;
+         esac
+         ;;
+   esac])
+
 # ARM
 # ===
 #
--- a/contrib/arm-neon/linux.c
+++ b/contrib/arm-neon/linux.c
@@ -1,8 +1,8 @@
 /* contrib/arm-neon/linux.c
 *
- * Copyright (c) 2014 Glenn Randers-Pehrson
- * Written by John Bowler, 2014.
- * Last changed in libpng 1.6.16 [December 22, 2014]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
+ * Copyright (c) 2014, 2017 Glenn Randers-Pehrson
+ * Written by John Bowler, 2014, 2017.
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -62,7 +62,7 @@ png_have_neon(png_structp png_ptr)

               counter=0;
               state = Feature;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */

            case Feature:
               /* Match 'FEATURE', ASCII case insensitive. */
@@ -75,7 +75,7 @@ png_have_neon(png_structp png_ptr)

               /* did not match 'feature' */
               state = SkipLine;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */

            case SkipLine:
            skipLine:
@@ -110,7 +110,7 @@ png_have_neon(png_structp png_ptr)

               state = Neon;
               counter = 0;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */

            case Neon:
               /* Look for 'neon' tag */
@@ -122,7 +122,7 @@ png_have_neon(png_structp png_ptr)
               }

               state = SkipTag;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */

            case SkipTag:
               /* Skip non-space characters */
--- a/contrib/gregbook/README
+++ b/contrib/gregbook/README
@@ -63,7 +63,7 @@ BUILD INSTRUCTIONS

 - Prerequisites (in order of compilation):

-      - zlib            http://zlib.net/
+      - zlib            https://zlib.net/
      - libpng          http://www.libpng.org/pub/png/libpng.html
      - pngbook         http://www.libpng.org/pub/png/book/sources.html

--- a/contrib/libtests/pngstest.c
+++ b/contrib/libtests/pngstest.c
@@ -1,9 +1,8 @@
 /*-
 * pngstest.c
 *
- * Copyright (c) 2013-2016 John Cunningham Bowler
- *
- * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
+ * Copyright (c) 2013-2017 John Cunningham Bowler
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -2746,22 +2745,27 @@ compare_two_images(Image *a, Image *b, int via_linear,
       */
      else if ((a->opts & ACCUMULATE) == 0)
      {
+#        ifdef __GNUC__
+#           define BYTE_CHARS 20 /* 2^32: GCC sprintf warning */
+#        else
+#           define BYTE_CHARS 3 /* 2^8: real maximum value */
+#        endif
         /* Check the original image first,
          * TODO: deal with input images with bad pixel values?
          */
         if (amax >= a->image.colormap_entries)
         {
-            char pindex[9];
-            sprintf(pindex, "%d[%lu]", amax,
-               (unsigned long)a->image.colormap_entries);
+            char pindex[3+2*BYTE_CHARS];
+            sprintf(pindex, "%d[%u]", amax,
+               (png_byte)/*SAFE*/a->image.colormap_entries);
            return logerror(a, a->file_name, ": bad pixel index: ", pindex);
         }

         else if (bmax >= b->image.colormap_entries)
         {
-            char pindex[9];
-            sprintf(pindex, "%d[%lu]", bmax,
-               (unsigned long)b->image.colormap_entries);
+            char pindex[3+2*BYTE_CHARS];
+            sprintf(pindex, "%d[%u]", bmax,
+               (png_byte)/*SAFE*/b->image.colormap_entries);
            return logerror(b, b->file_name, ": bad pixel index: ", pindex);
         }
      }
@@ -2881,10 +2885,13 @@ compare_two_images(Image *a, Image *b, int via_linear,
               {
                  case 4:
                     if (pua[btoa[3]] != pub[3]) break;
+                     /* FALLTHROUGH */
                  case 3:
                     if (pua[btoa[2]] != pub[2]) break;
+                     /* FALLTHROUGH */
                  case 2:
                     if (pua[btoa[1]] != pub[1]) break;
+                     /* FALLTHROUGH */
                  case 1:
                     if (pua[btoa[0]] != pub[0]) break;
                     if (alpha_added != 4 && pub[alpha_added] != 65535) break;
@@ -2900,10 +2907,13 @@ compare_two_images(Image *a, Image *b, int via_linear,
               {
                  case 4:
                     if (psa[btoa[3]] != psb[3]) break;
+                     /* FALLTHROUGH */
                  case 3:
                     if (psa[btoa[2]] != psb[2]) break;
+                     /* FALLTHROUGH */
                  case 2:
                     if (psa[btoa[1]] != psb[1]) break;
+                     /* FALLTHROUGH */
                  case 1:
                     if (psa[btoa[0]] != psb[0]) break;
                     if (alpha_added != 4 && psb[alpha_added] != 255) break;
--- a/contrib/libtests/pngunknown.c
+++ b/contrib/libtests/pngunknown.c
@@ -1,8 +1,8 @@

 /* pngunknown.c - test the read side unknown chunk handling
 *
- * Last changed in libpng 1.6.26 [October 20, 2016]
- * Copyright (c) 2015,2016 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
+ * Copyright (c) 2015,2017 Glenn Randers-Pehrson
 * Written by John Cunningham Bowler
 *
 * This code is released under the libpng license.
@@ -614,7 +614,7 @@ get_unknown(display *d, png_infop info_ptr, int after_IDAT)
                  ++(d->error_count);
                  break;
               }
-               /* FALL THROUGH (safe) */
+               /* FALLTHROUGH */ /* (safe) */
            case PNG_HANDLE_CHUNK_ALWAYS:
               break;
         }
--- a/contrib/libtests/pngvalid.c
+++ b/contrib/libtests/pngvalid.c
@@ -1,7 +1,7 @@

 /* pngvalid.c - validate libpng by constructing then reading png files.
 *
- * Last changed in libpng 1.6.29 [March 16, 2017]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
 * Copyright (c) 2014-2017 John Cunningham Bowler
 *
 * This code is released under the libpng license.
@@ -6584,16 +6584,16 @@ transform_info_imp(transform_display *dp, png_structp pp, png_infop pi)
   {
   case PNG_COLOR_TYPE_PALETTE:
      if (dp->output_bit_depth > 8) goto error;
-      /*FALL THROUGH*/
+      /* FALLTHROUGH */
   case PNG_COLOR_TYPE_GRAY:
      if (dp->output_bit_depth == 1 || dp->output_bit_depth == 2 ||
         dp->output_bit_depth == 4)
         break;
-      /*FALL THROUGH*/
+      /* FALLTHROUGH */
   default:
      if (dp->output_bit_depth == 8 || dp->output_bit_depth == 16)
         break;
-      /*FALL THROUGH*/
+      /* FALLTHROUGH */
   error:
      {
         char message[128];
@@ -9994,9 +9994,9 @@ gamma_component_validate(const char *name, const validate_info *vi,
               case PNG_BACKGROUND_GAMMA_FILE:
               case PNG_BACKGROUND_GAMMA_UNIQUE:
                  use_background = (alpha >= 0 && alpha < 1);
-                  /*FALL THROUGH*/
 #           endif
 #           ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+               /* FALLTHROUGH */
               case ALPHA_MODE_OFFSET + PNG_ALPHA_STANDARD:
               case ALPHA_MODE_OFFSET + PNG_ALPHA_BROKEN:
               case ALPHA_MODE_OFFSET + PNG_ALPHA_OPTIMIZED:
--- a/contrib/testpngs/makepngs.sh
+++ b/contrib/testpngs/makepngs.sh
@@ -5,7 +5,7 @@

 # Copyright (c) 2015 John Cunningham Bowler

-# Last changed in libpng 1.7.0 [(PENDING RELEASE)]
+# Last changed in libpng 1.6.20 [December 3, 2015]

 # This code is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
--- a/contrib/tools/pngfix.c
+++ b/contrib/tools/pngfix.c
@@ -1,8 +1,7 @@
 /* pngfix.c
 *
- * Copyright (c) 2014-2016 John Cunningham Bowler
- *
- * Last changed in libpng 1.6.26 [October 20, 2016]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
+ * Copyright (c) 2014-2017 John Cunningham Bowler
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -2416,7 +2415,7 @@ zlib_advance(struct zlib *zlib, png_uint_32 nbytes)
                  endrc = ZLIB_TOO_FAR_BACK;
                  break;
               }
-               /* FALL THROUGH */
+               /* FALLTHROUGH */

            default:
               zlib_message(zlib, 0/*stream error*/);
@@ -2570,7 +2569,7 @@ zlib_run(struct zlib *zlib)
                  list->lengths[i] -= zlib->extra_bytes;
                  list->count = i+1;
                  zlib->idat->idat_list_tail = list;
-                  /* FALL THROUGH */
+                  /* FALLTHROUGH */

               default:
                  return rc;
@@ -2673,7 +2672,7 @@ zlib_check(struct file *file, png_uint_32 offset)
            /* Truncated stream; unrecoverable, gets converted to ZLIB_FATAL */
            zlib.z.msg = PNGZ_MSG_CAST("[truncated]");
            zlib_message(&zlib, 0/*expected*/);
-            /* FALL THROUGH */
+            /* FALLTHROUGH */

         default:
            /* Unrecoverable error; skip the chunk; a zlib_message has already
@@ -3341,7 +3340,7 @@ read_callback(png_structp png_ptr, png_bytep buffer, size_t count)
               if (file->state != STATE_IDAT && length > 0)
                  setpos(chunk);
            }
-            /* FALL THROUGH */
+            /* FALLTHROUGH */

         default:
            assert(chunk != NULL);
--- a/intel/filter_sse2_intrinsics.c
+++ b/intel/filter_sse2_intrinsics.c
@@ -5,7 +5,7 @@
 * Written by Mike Klein and Matt Sarett
 * Derived from arm/filter_neon_intrinsics.c
 *
- * Last changed in libpng 1.6.29 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -40,7 +40,7 @@ static __m128i load3(const void* p) {
   /* We'll load 2 bytes, then 1 byte,
    * then mask them together, and finally load into SSE.
    */
-   const png_uint_16* p01 = p;
+   const png_uint_16* p01 = (png_const_uint_16p)p;
   const png_byte*    p2  = (const png_byte*)(p01+1);

   png_uint_32 v012 = (png_uint_32)(*p01)
@@ -53,12 +53,15 @@ static void store3(void* p, __m128i v) {
    * its bottom two bytes, then its third byte.
    */
   png_uint_32 v012;
+   png_uint_16* p01;
+   png_byte*    p2;
+
   store4(&v012, v);

-   png_uint_16* p01 = p;
-   png_byte*    p2  = (png_byte*)(p01+1);
-   *p01 = v012;
-   *p2  = v012 >> 16;
+   p01 = (png_uint_16p)p;
+   p2  = (png_byte*)(p01+1);
+   *p01 = (png_uint_16)v012;
+   *p2  = (png_byte)(v012 >> 16);
 }

 void png_read_filter_row_sub3_sse2(png_row_infop row_info, png_bytep row,
@@ -68,10 +71,13 @@ void png_read_filter_row_sub3_sse2(png_row_infop row_info, png_bytep row,
    * There is no pixel to the left of the first pixel.  It's encoded directly.
    * That works with our main loop if we just say that left pixel was zero.
    */
-   png_debug(1, "in png_read_filter_row_sub3_sse2");
+   png_size_t rb;
+
   __m128i a, d = _mm_setzero_si128();

-   int rb = row_info->rowbytes;
+   png_debug(1, "in png_read_filter_row_sub3_sse2");
+
+   rb = row_info->rowbytes;
   while (rb >= 4) {
      a = d; d = load4(row);
      d = _mm_add_epi8(d, a);
@@ -88,6 +94,7 @@ void png_read_filter_row_sub3_sse2(png_row_infop row_info, png_bytep row,
      row += 3;
      rb  -= 3;
   }
+   PNG_UNUSED(prev)
 }

 void png_read_filter_row_sub4_sse2(png_row_infop row_info, png_bytep row,
@@ -97,11 +104,14 @@ void png_read_filter_row_sub4_sse2(png_row_infop row_info, png_bytep row,
    * There is no pixel to the left of the first pixel.  It's encoded directly.
    * That works with our main loop if we just say that left pixel was zero.
    */
-   png_debug(1, "in png_read_filter_row_sub4_sse2");
+   png_size_t rb;
+
   __m128i a, d = _mm_setzero_si128();

-   int rb = row_info->rowbytes;
-   while (rb > 0) {
+   png_debug(1, "in png_read_filter_row_sub4_sse2");
+
+   rb = row_info->rowbytes+4;
+   while (rb > 4) {
      a = d; d = load4(row);
      d = _mm_add_epi8(d, a);
      store4(row, d);
@@ -109,6 +119,7 @@ void png_read_filter_row_sub4_sse2(png_row_infop row_info, png_bytep row,
      row += 4;
      rb  -= 4;
   }
+   PNG_UNUSED(prev)
 }

 void png_read_filter_row_avg3_sse2(png_row_infop row_info, png_bytep row,
@@ -119,18 +130,23 @@ void png_read_filter_row_avg3_sse2(png_row_infop row_info, png_bytep row,
    * predicted to be half of the pixel above it.  So again, this works
    * perfectly with our loop if we make sure a starts at zero.
    */
-   png_debug(1, "in png_read_filter_row_avg3_sse2");
+
+   png_size_t rb;
+
   const __m128i zero = _mm_setzero_si128();
+
   __m128i    b;
   __m128i a, d = zero;

-   int rb = row_info->rowbytes;
+   png_debug(1, "in png_read_filter_row_avg3_sse2");
+   rb = row_info->rowbytes;
   while (rb >= 4) {
+      __m128i avg;
             b = load4(prev);
      a = d; d = load4(row );

      /* PNG requires a truncating average, so we can't just use _mm_avg_epu8 */
-      __m128i avg = _mm_avg_epu8(a,b);
+      avg = _mm_avg_epu8(a,b);
      /* ...but we can fix it up by subtracting off 1 if it rounded up. */
      avg = _mm_sub_epi8(avg, _mm_and_si128(_mm_xor_si128(a,b),
                                            _mm_set1_epi8(1)));
@@ -142,11 +158,12 @@ void png_read_filter_row_avg3_sse2(png_row_infop row_info, png_bytep row,
      rb   -= 3;
   }
   if (rb > 0) {
+      __m128i avg;
             b = load3(prev);
      a = d; d = load3(row );

      /* PNG requires a truncating average, so we can't just use _mm_avg_epu8 */
-      __m128i avg = _mm_avg_epu8(a,b);
+      avg = _mm_avg_epu8(a,b);
      /* ...but we can fix it up by subtracting off 1 if it rounded up. */
      avg = _mm_sub_epi8(avg, _mm_and_si128(_mm_xor_si128(a,b),
                                            _mm_set1_epi8(1)));
@@ -168,18 +185,21 @@ void png_read_filter_row_avg4_sse2(png_row_infop row_info, png_bytep row,
    * predicted to be half of the pixel above it.  So again, this works
    * perfectly with our loop if we make sure a starts at zero.
    */
-   png_debug(1, "in png_read_filter_row_avg4_sse2");
+   png_size_t rb;
   const __m128i zero = _mm_setzero_si128();
   __m128i    b;
   __m128i a, d = zero;

-   int rb = row_info->rowbytes;
-   while (rb > 0) {
+   png_debug(1, "in png_read_filter_row_avg4_sse2");
+
+   rb = row_info->rowbytes+4;
+   while (rb > 4) {
+      __m128i avg;
             b = load4(prev);
      a = d; d = load4(row );

      /* PNG requires a truncating average, so we can't just use _mm_avg_epu8 */
-      __m128i avg = _mm_avg_epu8(a,b);
+      avg = _mm_avg_epu8(a,b);
      /* ...but we can fix it up by subtracting off 1 if it rounded up. */
      avg = _mm_sub_epi8(avg, _mm_and_si128(_mm_xor_si128(a,b),
                                            _mm_set1_epi8(1)));
@@ -237,38 +257,42 @@ void png_read_filter_row_paeth3_sse2(png_row_infop row_info, png_bytep row,
    * Here we zero b and d, which become c and a respectively at the start of
    * the loop.
    */
-   png_debug(1, "in png_read_filter_row_paeth3_sse2");
+   png_size_t rb;
   const __m128i zero = _mm_setzero_si128();
   __m128i c, b = zero,
           a, d = zero;

-   int rb = row_info->rowbytes;
+   png_debug(1, "in png_read_filter_row_paeth3_sse2");
+
+   rb = row_info->rowbytes;
   while (rb >= 4) {
      /* It's easiest to do this math (particularly, deal with pc) with 16-bit
       * intermediates.
       */
+      __m128i pa,pb,pc,smallest,nearest;
      c = b; b = _mm_unpacklo_epi8(load4(prev), zero);
      a = d; d = _mm_unpacklo_epi8(load4(row ), zero);

      /* (p-a) == (a+b-c - a) == (b-c) */
-      __m128i pa = _mm_sub_epi16(b,c);
+   
+      pa = _mm_sub_epi16(b,c);

      /* (p-b) == (a+b-c - b) == (a-c) */
-      __m128i pb = _mm_sub_epi16(a,c);
+      pb = _mm_sub_epi16(a,c);

      /* (p-c) == (a+b-c - c) == (a+b-c-c) == (b-c)+(a-c) */
-      __m128i pc = _mm_add_epi16(pa,pb);
+      pc = _mm_add_epi16(pa,pb);

      pa = abs_i16(pa);  /* |p-a| */
      pb = abs_i16(pb);  /* |p-b| */
      pc = abs_i16(pc);  /* |p-c| */

-      __m128i smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));
+      smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));

      /* Paeth breaks ties favoring a over b over c. */
-      __m128i nearest  = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
-                         if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
-                                                                     c));
+      nearest  = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
+                 if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
+                                                             c));

      /* Note `_epi8`: we need addition to wrap modulo 255. */
      d = _mm_add_epi8(d, nearest);
@@ -282,26 +306,27 @@ void png_read_filter_row_paeth3_sse2(png_row_infop row_info, png_bytep row,
      /* It's easiest to do this math (particularly, deal with pc) with 16-bit
       * intermediates.
       */
+      __m128i pa,pb,pc,smallest,nearest;
      c = b; b = _mm_unpacklo_epi8(load3(prev), zero);
      a = d; d = _mm_unpacklo_epi8(load3(row ), zero);

      /* (p-a) == (a+b-c - a) == (b-c) */
-      __m128i pa = _mm_sub_epi16(b,c);
+      pa = _mm_sub_epi16(b,c);

      /* (p-b) == (a+b-c - b) == (a-c) */
-      __m128i pb = _mm_sub_epi16(a,c);
+      pb = _mm_sub_epi16(a,c);

      /* (p-c) == (a+b-c - c) == (a+b-c-c) == (b-c)+(a-c) */
-      __m128i pc = _mm_add_epi16(pa,pb);
+      pc = _mm_add_epi16(pa,pb);

      pa = abs_i16(pa);  /* |p-a| */
      pb = abs_i16(pb);  /* |p-b| */
      pc = abs_i16(pc);  /* |p-c| */

-      __m128i smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));
+      smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));

      /* Paeth breaks ties favoring a over b over c. */
-      __m128i nearest  = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
+      nearest  = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
                         if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
                                                                     c));

@@ -331,13 +356,16 @@ void png_read_filter_row_paeth4_sse2(png_row_infop row_info, png_bytep row,
    * Here we zero b and d, which become c and a respectively at the start of
    * the loop.
    */
-   png_debug(1, "in png_read_filter_row_paeth4_sse2");
+   png_size_t rb;
   const __m128i zero = _mm_setzero_si128();
+   __m128i pa,pb,pc,smallest,nearest;
   __m128i c, b = zero,
           a, d = zero;

-   int rb = row_info->rowbytes;
-   while (rb > 0) {
+   png_debug(1, "in png_read_filter_row_paeth4_sse2");
+
+   rb = row_info->rowbytes+4;
+   while (rb > 4) {
      /* It's easiest to do this math (particularly, deal with pc) with 16-bit
       * intermediates.
       */
@@ -345,22 +373,22 @@ void png_read_filter_row_paeth4_sse2(png_row_infop row_info, png_bytep row,
      a = d; d = _mm_unpacklo_epi8(load4(row ), zero);

      /* (p-a) == (a+b-c - a) == (b-c) */
-      __m128i pa = _mm_sub_epi16(b,c);
+      pa = _mm_sub_epi16(b,c);

      /* (p-b) == (a+b-c - b) == (a-c) */
-      __m128i pb = _mm_sub_epi16(a,c);
+      pb = _mm_sub_epi16(a,c);

      /* (p-c) == (a+b-c - c) == (a+b-c-c) == (b-c)+(a-c) */
-      __m128i pc = _mm_add_epi16(pa,pb);
+      pc = _mm_add_epi16(pa,pb);

      pa = abs_i16(pa);  /* |p-a| */
      pb = abs_i16(pb);  /* |p-b| */
      pc = abs_i16(pc);  /* |p-c| */

-      __m128i smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));
+      smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));

      /* Paeth breaks ties favoring a over b over c. */
-      __m128i nearest  = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
+      nearest  = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
                         if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
                                                                     c));

--- a/intel/intel_init.c
+++ b/intel/intel_init.c
@@ -5,7 +5,7 @@
 * Written by Mike Klein and Matt Sarett, Google, Inc.
 * Derived from arm/arm_init.c
 *
- * Last changed in libpng 1.6.29 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.29 [March 16, 2017]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -1,9 +1,9 @@
 libpng-manual.txt - A description on how to use and modify libpng

- libpng version 1.6.30beta03 - May 22, 2017
+ libpng version 1.6.31beta04 - July 11, 2017
 Updated and distributed by Glenn Randers-Pehrson
 <glennrp at users.sourceforge.net>
- Copyright (c) 1998-2016 Glenn Randers-Pehrson
+ Copyright (c) 1998-2017 Glenn Randers-Pehrson

 This document is released under the libpng license.
 For conditions of distribution and use, see the disclaimer
@@ -11,9 +11,9 @@ libpng-manual.txt - A description on how to use and modify libpng

 Based on:

- libpng versions 0.97, January 1998, through 1.6.30beta03 - May 22, 2017
+ libpng versions 0.97, January 1998, through 1.6.31beta04 - July 11, 2017
 Updated and distributed by Glenn Randers-Pehrson
- Copyright (c) 1998-2016 Glenn Randers-Pehrson
+ Copyright (c) 1998-2017 Glenn Randers-Pehrson

 libpng 1.0 beta 6 - version 0.96 - May 28, 1997
 Updated and distributed by Andreas Dilger
@@ -101,7 +101,7 @@ majority of the needs of its users.

 Libpng uses zlib for its compression and decompression of PNG files.
 Further information about zlib, and the latest version of zlib, can
-be found at the zlib home page, <http://zlib.net/>.
+be found at the zlib home page, <https://zlib.net/>.
 The zlib compression utility is a general purpose utility that is
 useful for more than PNG files, and can be used without libpng.
 See the documentation delivered with zlib for more details.
@@ -1330,6 +1330,11 @@ in until png_read_end() has read the chunk data following the image.
    rowbytes = png_get_rowbytes(png_ptr, info_ptr);

    rowbytes       - number of bytes needed to hold a row
+                     This value, the bit_depth, color_type,
+                     and the number of channels can change
+                     if you use transforms such as
+                     png_set_expand(). See
+                     png_read_update_info(), below.

    signature = png_get_signature(png_ptr, info_ptr);

@@ -5216,11 +5221,13 @@ control.  The git repository was built from old libpng-x.y.z.tar.gz files
 going back to version 0.70.  You can access the git repository (read only)
 at

-    git://git.code.sf.net/p/libpng/code.git
+    https://github.com/glennrp/libpng or
+    https://git.code.sf.net/p/libpng/code.git

-or you can browse it with a web browser by selecting the "code" button at
+or you can browse it with a web browser at

-    https://sourceforge.net/projects/libpng
+    https://github.com/glennrp/libpng or
+    https://sourceforge.net/p/libpng/code/ci/libpng16/tree/

 Patches can be sent to glennrp at users.sourceforge.net or to
 png-mng-implement at lists.sourceforge.net or you can upload them to
@@ -5228,10 +5235,14 @@ the libpng bug tracker at

    https://libpng.sourceforge.io/

+or as a "pull request" to
+
+    https://github.com/glennrp/libpng/pulls
+
 We also accept patches built from the tar or zip distributions, and
 simple verbal discriptions of bug fixes, reported either to the
 SourceForge bug tracker, to the png-mng-implement at lists.sf.net
-mailing list, or directly to glennrp.
+mailing list, as github issues, or directly to glennrp.

 XV. Coding style

@@ -5377,7 +5388,7 @@ Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.

 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.6.30beta03 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.31beta04 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.

 Libpng only has two year fields.  One is a 2-byte unsigned integer
--- a/libpng.3
+++ b/libpng.3
@@ -1,6 +1,6 @@
-.TH LIBPNG 3 "May 22, 2017"
+.TH LIBPNG 3 "July 11, 2017"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.30beta03
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.31beta04
 .SH SYNOPSIS
 \fB
 #include <png.h>\fP
@@ -510,10 +510,10 @@ Following is a copy of the libpng-manual.txt file that accompanies libpng.
 .SH LIBPNG.TXT
 libpng-manual.txt - A description on how to use and modify libpng

- libpng version 1.6.30beta03 - May 22, 2017
+ libpng version 1.6.31beta04 - July 11, 2017
 Updated and distributed by Glenn Randers-Pehrson
 <glennrp at users.sourceforge.net>
- Copyright (c) 1998-2016 Glenn Randers-Pehrson
+ Copyright (c) 1998-2017 Glenn Randers-Pehrson

 This document is released under the libpng license.
 For conditions of distribution and use, see the disclaimer
@@ -521,9 +521,9 @@ libpng-manual.txt - A description on how to use and modify libpng

 Based on:

- libpng versions 0.97, January 1998, through 1.6.30beta03 - May 22, 2017
+ libpng versions 0.97, January 1998, through 1.6.31beta04 - July 11, 2017
 Updated and distributed by Glenn Randers-Pehrson
- Copyright (c) 1998-2016 Glenn Randers-Pehrson
+ Copyright (c) 1998-2017 Glenn Randers-Pehrson

 libpng 1.0 beta 6 - version 0.96 - May 28, 1997
 Updated and distributed by Andreas Dilger
@@ -611,7 +611,7 @@ majority of the needs of its users.

 Libpng uses zlib for its compression and decompression of PNG files.
 Further information about zlib, and the latest version of zlib, can
-be found at the zlib home page, <http://zlib.net/>.
+be found at the zlib home page, <https://zlib.net/>.
 The zlib compression utility is a general purpose utility that is
 useful for more than PNG files, and can be used without libpng.
 See the documentation delivered with zlib for more details.
@@ -1840,6 +1840,11 @@ in until png_read_end() has read the chunk data following the image.
    rowbytes = png_get_rowbytes(png_ptr, info_ptr);

    rowbytes       - number of bytes needed to hold a row
+                     This value, the bit_depth, color_type,
+                     and the number of channels can change
+                     if you use transforms such as
+                     png_set_expand(). See
+                     png_read_update_info(), below.

    signature = png_get_signature(png_ptr, info_ptr);

@@ -5726,11 +5731,13 @@ control.  The git repository was built from old libpng-x.y.z.tar.gz files
 going back to version 0.70.  You can access the git repository (read only)
 at

-    git://git.code.sf.net/p/libpng/code.git
+    https://github.com/glennrp/libpng or
+    https://git.code.sf.net/p/libpng/code.git

-or you can browse it with a web browser by selecting the "code" button at
+or you can browse it with a web browser at

-    https://sourceforge.net/projects/libpng
+    https://github.com/glennrp/libpng or
+    https://sourceforge.net/p/libpng/code/ci/libpng16/tree/

 Patches can be sent to glennrp at users.sourceforge.net or to
 png-mng-implement at lists.sourceforge.net or you can upload them to
@@ -5738,10 +5745,14 @@ the libpng bug tracker at

    https://libpng.sourceforge.io/

+or as a "pull request" to
+
+    https://github.com/glennrp/libpng/pulls
+
 We also accept patches built from the tar or zip distributions, and
 simple verbal discriptions of bug fixes, reported either to the
 SourceForge bug tracker, to the png-mng-implement at lists.sf.net
-mailing list, or directly to glennrp.
+mailing list, as github issues, or directly to glennrp.

 .SH XV. Coding style

@@ -5887,7 +5898,7 @@ Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.

 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.6.30beta03 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.31beta04 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.

 Libpng only has two year fields.  One is a 2-byte unsigned integer
@@ -5989,7 +6000,7 @@ the first widely used release:
 ...
 1.5.28                  15    10528  15.so.15.28[.0]
 ...
- 1.6.30                  16    10630  16.so.16.30[.0]
+ 1.6.31                  16    10631  16.so.16.31[.0]

 Henceforth the source version will match the shared-library minor
 and patch numbers; the shared-library major version number will be
@@ -6016,7 +6027,7 @@ http://www.libpng.org/pub/png
 .I libpng
 or at
 .br
-http://zlib.net/
+https://zlib.net/

 .LP
 .IR PNG specification: RFC 2083
@@ -6045,7 +6056,7 @@ possible without all of you.

 Thanks to Frank J. T. Wojcik for helping with the documentation.

-Libpng version 1.6.30beta03 - May 22, 2017:
+Libpng version 1.6.31beta04 - July 11, 2017:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).

@@ -6070,7 +6081,7 @@ this sentence.

 This code is released under the libpng license.

-libpng versions 1.0.7, July 1, 2000 through 1.6.30beta03, May 22, 2017 are
+libpng versions 1.0.7, July 1, 2000 through 1.6.31beta04, July 11, 2017 are
 Copyright (c) 2000-2002, 2004, 2006-2017 Glenn Randers-Pehrson, are
 derived from libpng-1.0.6, and are distributed according to the same
 disclaimer and license as libpng-1.0.6 with the following individuals
@@ -6198,7 +6209,7 @@ files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).

 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-May 22, 2017
+July 11, 2017

 .\" end of man page

--- a/libpng.pc.in
+++ b/libpng.pc.in
@@ -6,6 +6,7 @@ includedir=@includedir@/libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@
 Name: libpng
 Description: Loads and saves PNG files
 Version: @PNGLIB_VERSION@
+Requires: zlib
 Libs: -L${libdir} -lpng@PNGLIB_MAJOR@@PNGLIB_MINOR@
 Libs.private: @LIBS@
 Cflags: -I${includedir}
--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,11 +1,11 @@
-.TH LIBPNGPF 3 "May 22, 2017"
+.TH LIBPNGPF 3 "April 1, 2017"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.30beta03
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.31beta04
 (private functions)
 .SH SYNOPSIS
-\fB#include \fI"pngpriv.h"
+\fB\fB#include \fI\fI"pngpriv.h"

-\fBAs of libpng version \fP\fI1.5.1\fP\fB, this section is no longer \fP\fImaintained\fP\fB, now that the private function prototypes are hidden in pngpriv.h and not accessible to applications. Look in pngpriv.h for the prototypes and a short description of each \fIfunction.
+\fB\fBAs of libpng version \fP\fI\fP\fI1.5.1\fP\fB\fP\fB, this section is no longer \fP\fI\fP\fImaintained\fP\fB\fP\fB, now that the private function prototypes are hidden in pngpriv.h and not accessible to applications. Look in pngpriv.h for the prototypes and a short description of each \fI\fIfunction.

 .SH DESCRIPTION
 The functions previously listed here are used privately by libpng and are not
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "May 22, 2017"
+.TH PNG 5 "April 1, 2017"
 .SH NAME
 png \- Portable Network Graphics (PNG) format
 .SH DESCRIPTION
--- a/png.c
+++ b/png.c
@@ -1,7 +1,7 @@

 /* png.c - location for general purpose libpng functions
 *
- * Last changed in libpng 1.6.30 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -14,7 +14,27 @@
 #include "pngpriv.h"

 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_30beta03 Your_png_h_is_not_version_1_6_30beta03;
+typedef png_libpng_version_1_6_31beta04 Your_png_h_is_not_version_1_6_31beta04;
+
+#ifdef __GNUC__
+/* The version tests may need to be added to, but the problem warning has
+ * consistently been fixed in GCC versions which obtain wide-spread release.
+ * The problem is that many versions of GCC rearrange comparison expressions in
+ * the optimizer in such a way that the results of the comparison will change
+ * if signed integer overflow occurs.  Such comparisons are not permitted in
+ * ANSI C90, however GCC isn't clever enough to work out that that do not occur
+ * below in png_ascii_from_fp and png_muldiv, so it produces a warning with
+ * -Wextra.  Unfortunately this is highly dependent on the optimizer and the
+ * machine architecture so the warning comes and goes unpredictably and is
+ * impossible to "fix", even were that a good idea.
+ */
+#if __GNUC__ == 7 && __GNUC_MINOR__ == 1
+#define GCC_STRICT_OVERFLOW 1
+#endif /* GNU 7.1.x */
+#endif /* GNU */
+#ifndef GCC_STRICT_OVERFLOW
+#define GCC_STRICT_OVERFLOW 0
+#endif

 /* Tells libpng that we have already handled the first "num_bytes" bytes
 * of the PNG file signature.  If the PNG data is embedded into another
@@ -776,14 +796,14 @@ png_get_copyright(png_const_structrp png_ptr)
 #else
 #  ifdef __STDC__
   return PNG_STRING_NEWLINE \
-      "libpng version 1.6.30beta03 - May 22, 2017" PNG_STRING_NEWLINE \
+      "libpng version 1.6.31beta04 - July 11, 2017" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson" \
      PNG_STRING_NEWLINE \
      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
      PNG_STRING_NEWLINE;
 #  else
-   return "libpng version 1.6.30beta03 - May 22, 2017\
+   return "libpng version 1.6.31beta04 - July 11, 2017\
      Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson\
      Copyright (c) 1996-1997 Andreas Dilger\
      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -2857,6 +2877,14 @@ png_pow10(int power)
 /* Function to format a floating point value in ASCII with a given
 * precision.
 */
+#if GCC_STRICT_OVERFLOW
+#pragma GCC diagnostic push
+/* The problem arises below with exp_b10, which can never overflow because it
+ * comes, originally, from frexp and is therefore limited to a range which is
+ * typically +/-710 (log2(DBL_MAX)/log2(DBL_MIN)).
+ */
+#pragma GCC diagnostic warning "-Wstrict-overflow=2"
+#endif /* GCC_STRICT_OVERFLOW */
 void /* PRIVATE */
 png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
    double fp, unsigned int precision)
@@ -2946,7 +2974,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
             */
            if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */
            {
-               czero = (unsigned int)(-exp_b10); /* PLUS 2 digits: TOTAL 3 */
+               czero = 0U-exp_b10; /* PLUS 2 digits: TOTAL 3 */
               exp_b10 = 0;      /* Dot added below before first output. */
            }
            else
@@ -3087,7 +3115,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,

            /* Check for an exponent, if we don't need one we are
             * done and just need to terminate the string.  At
-             * this point exp_b10==(-1) is effectively if flag - it got
+             * this point exp_b10==(-1) is effectively a flag - it got
             * to '-1' because of the decrement after outputting
             * the decimal point above (the exponent required is
             * *not* -1!)
@@ -3101,7 +3129,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
                * zeros were *not* output, so this doesn't increase
                * the output count.
                */
-               while (--exp_b10 >= 0) *ascii++ = 48;
+               while (exp_b10-- > 0) *ascii++ = 48;

               *ascii = 0;

@@ -3131,11 +3159,11 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
               if (exp_b10 < 0)
               {
                  *ascii++ = 45; --size; /* '-': PLUS 1 TOTAL 3+precision */
-                  uexp_b10 = (unsigned int)(-exp_b10);
+                  uexp_b10 = 0U-exp_b10;
               }

               else
-                  uexp_b10 = (unsigned int)exp_b10;
+                  uexp_b10 = 0U+exp_b10;

               cdigits = 0;

@@ -3178,6 +3206,9 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
   /* Here on buffer too small. */
   png_error(png_ptr, "ASCII conversion buffer too small");
 }
+#if GCC_STRICT_OVERFLOW
+#pragma GCC diagnostic pop
+#endif /* GCC_STRICT_OVERFLOW */

 #  endif /* FLOATING_POINT */

@@ -3291,6 +3322,15 @@ png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)
 * the nearest .00001).  Overflow and divide by zero are signalled in
 * the result, a boolean - true on success, false on overflow.
 */
+#if GCC_STRICT_OVERFLOW /* from above */
+/* It is not obvious which comparison below gets optimized in such a way that
+ * signed overflow would change the result; looking through the code does not
+ * reveal any tests which have the form GCC complains about, so presumably the
+ * optimizer is moving an add or subtract into the 'if' somewhere.
+ */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic warning "-Wstrict-overflow=2"
+#endif /* GCC_STRICT_OVERFLOW */
 int
 png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
    png_int_32 divisor)
@@ -3405,6 +3445,9 @@ png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,

   return 0;
 }
+#if GCC_STRICT_OVERFLOW
+#pragma GCC diagnostic pop
+#endif /* GCC_STRICT_OVERFLOW */
 #endif /* READ_GAMMA || INCH_CONVERSIONS */

 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@

 /* png.h - header file for PNG reference library
 *
- * libpng version 1.6.30beta03, May 22, 2017
+ * libpng version 1.6.31beta04, July 11, 2017
 *
 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -12,7 +12,7 @@
 * Authors and maintainers:
 *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
 *   libpng versions 0.89, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.6.30beta03, May 22, 2017:
+ *   libpng versions 0.97, January 1998, through 1.6.31beta04, July 11, 2017:
 *     Glenn Randers-Pehrson.
 *   See also "Contributing Authors", below.
 */
@@ -25,7 +25,7 @@
 *
 * This code is released under the libpng license.
 *
- * libpng versions 1.0.7, July 1, 2000 through 1.6.30beta03, May 22, 2017 are
+ * libpng versions 1.0.7, July 1, 2000 through 1.6.31beta04, July 11, 2017 are
 * Copyright (c) 2000-2002, 2004, 2006-2017 Glenn Randers-Pehrson, are
 * derived from libpng-1.0.6, and are distributed according to the same
 * disclaimer and license as libpng-1.0.6 with the following individuals
@@ -213,7 +213,7 @@
 *    ...
 *    1.5.28                  15    10527  15.so.15.28[.0]
 *    ...
- *    1.6.30                  16    10630  16.so.16.30[.0]
+ *    1.6.31                  16    10631  16.so.16.31[.0]
 *
 *    Henceforth the source version will match the shared-library major
 *    and minor numbers; the shared-library major version number will be
@@ -241,13 +241,13 @@
 * Y2K compliance in libpng:
 * =========================
 *
- *    May 22, 2017
+ *    July 11, 2017
 *
 *    Since the PNG Development group is an ad-hoc body, we can't make
 *    an official declaration.
 *
 *    This is your unofficial assurance that libpng from version 0.71 and
- *    upward through 1.6.30beta03 are Y2K compliant.  It is my belief that
+ *    upward through 1.6.31beta04 are Y2K compliant.  It is my belief that
 *    earlier versions were also Y2K compliant.
 *
 *    Libpng only has two year fields.  One is a 2-byte unsigned integer
@@ -309,8 +309,8 @@
 */

 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.6.30beta03"
-#define PNG_HEADER_VERSION_STRING " libpng version 1.6.30beta03 - May 22, 2017\n"
+#define PNG_LIBPNG_VER_STRING "1.6.31beta04"
+#define PNG_HEADER_VERSION_STRING " libpng version 1.6.31beta04 - July 11, 2017\n"

 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -318,13 +318,13 @@
 /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
 #define PNG_LIBPNG_VER_MAJOR   1
 #define PNG_LIBPNG_VER_MINOR   6
-#define PNG_LIBPNG_VER_RELEASE 30
+#define PNG_LIBPNG_VER_RELEASE 31

 /* This should match the numeric part of the final component of
 * PNG_LIBPNG_VER_STRING, omitting any leading zero:
 */

-#define PNG_LIBPNG_VER_BUILD  03
+#define PNG_LIBPNG_VER_BUILD  04

 /* Release Status */
 #define PNG_LIBPNG_BUILD_ALPHA    1
@@ -349,7 +349,7 @@
 * version 1.0.0 was mis-numbered 100 instead of 10000).  From
 * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release
 */
-#define PNG_LIBPNG_VER 10630 /* 1.6.30 */
+#define PNG_LIBPNG_VER 10631 /* 1.6.31 */

 /* Library configuration: these options cannot be changed after
 * the library has been built.
@@ -459,7 +459,7 @@ extern "C" {
 /* This triggers a compiler error in png.c, if png.c and png.h
 * do not agree upon the version number.
 */
-typedef char* png_libpng_version_1_6_30beta03;
+typedef char* png_libpng_version_1_6_31beta04;

 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
 *
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@

 /* pngconf.h - machine configurable file for libpng
 *
- * libpng version 1.6.30beta03, May 22, 2017
+ * libpng version 1.6.31beta04, July 11, 2017
 *
 * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
--- a/pngerror.c
+++ b/pngerror.c
@@ -1,8 +1,8 @@

 /* pngerror.c - stub functions for i/o and memory allocation
 *
- * Last changed in libpng 1.6.26 [October 20, 2016]
- * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
+ * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@@ -163,7 +163,7 @@ png_format_number(png_const_charp start, png_charp end, int format,
         case PNG_NUMBER_FORMAT_02u:
            /* Expects at least 2 digits. */
            mincount = 2;
-            /* FALL THROUGH */
+            /* FALLTHROUGH */

         case PNG_NUMBER_FORMAT_u:
            *--end = digits[number % 10];
@@ -173,7 +173,7 @@ png_format_number(png_const_charp start, png_charp end, int format,
         case PNG_NUMBER_FORMAT_02x:
            /* This format expects at least two digits */
            mincount = 2;
-            /* FALL THROUGH */
+            /* FALLTHROUGH */

         case PNG_NUMBER_FORMAT_x:
            *--end = digits[number & 0xf];
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1,7 +1,7 @@

 /* pngpriv.h - private declarations for use inside libpng
 *
- * Last changed in libpng 1.6.30 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -35,7 +35,9 @@
 * Windows/Visual Studio) there is no effect; the OS specific tests below are
 * still required (as of 2011-05-02.)
 */
-#define _POSIX_SOURCE 1 /* Just the POSIX 1003.1 and C89 APIs */
+#ifndef _POSIX_SOURCE
+# define _POSIX_SOURCE 1 /* Just the POSIX 1003.1 and C89 APIs */
+#endif

 #ifndef PNG_VERSION_INFO_ONLY
 /* Standard library headers not required by png.h: */
@@ -452,6 +454,21 @@
 #  define png_fixed_error(s1,s2) png_err(s1)
 #endif

+/* Some fixed point APIs are still required even if not exported because
+ * they get used by the corresponding floating point APIs.  This magic
+ * deals with this:
+ */
+#ifdef PNG_FIXED_POINT_SUPPORTED
+#  define PNGFAPI PNGAPI
+#else
+#  define PNGFAPI /* PRIVATE */
+#endif
+
+#ifndef PNG_VERSION_INFO_ONLY
+/* Other defines specific to compilers can go here.  Try to keep
+ * them inside an appropriate ifdef/endif pair for portability.
+ */
+
 /* C allows up-casts from (void*) to any pointer and (const void*) to any
 * pointer to a const object.  C++ regards this as a type error and requires an
 * explicit, static, cast and provides the static_cast<> rune to ensure that
@@ -480,20 +497,6 @@
 #  define png_aligncastconst(type, value) ((const void*)(value))
 #endif /* __cplusplus */

-/* Some fixed point APIs are still required even if not exported because
- * they get used by the corresponding floating point APIs.  This magic
- * deals with this:
- */
-#ifdef PNG_FIXED_POINT_SUPPORTED
-#  define PNGFAPI PNGAPI
-#else
-#  define PNGFAPI /* PRIVATE */
-#endif
-
-#ifndef PNG_VERSION_INFO_ONLY
-/* Other defines specific to compilers can go here.  Try to keep
- * them inside an appropriate ifdef/endif pair for portability.
- */
 #if defined(PNG_FLOATING_POINT_SUPPORTED) ||\
    defined(PNG_FLOATING_ARITHMETIC_SUPPORTED)
   /* png.c requires the following ANSI-C constants if the conversion of
--- a/pngread.c
+++ b/pngread.c
@@ -1,8 +1,8 @@

 /* pngread.c - read a PNG file
 *
- * Last changed in libpng 1.6.26 [October 20, 2016]
- * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
+ * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@@ -1883,7 +1883,7 @@ png_create_colormap_entry(png_image_read_control *display,
         {
            case 4:
               entry[afirst ? 0 : 3] = (png_uint_16)alpha;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */

            case 3:
               if (alpha < 65535)
@@ -1905,7 +1905,7 @@ png_create_colormap_entry(png_image_read_control *display,

            case 2:
               entry[1 ^ afirst] = (png_uint_16)alpha;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */

            case 1:
               if (alpha < 65535)
@@ -1934,6 +1934,7 @@ png_create_colormap_entry(png_image_read_control *display,
         {
            case 4:
               entry[afirst ? 0 : 3] = (png_byte)alpha;
+               /* FALLTHROUGH */
            case 3:
               entry[afirst + (2 ^ bgr)] = (png_byte)blue;
               entry[afirst + 1] = (png_byte)green;
@@ -1942,6 +1943,7 @@ png_create_colormap_entry(png_image_read_control *display,

            case 2:
               entry[1 ^ afirst] = (png_byte)alpha;
+               /* FALLTHROUGH */
            case 1:
               entry[afirst] = (png_byte)green;
               break;
@@ -2861,7 +2863,7 @@ png_image_read_colormap(png_voidp argument)
      case P_sRGB:
         /* Change to 8-bit sRGB */
         png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
-         /* FALL THROUGH */
+         /* FALLTHROUGH */

      case P_FILE:
         if (png_ptr->bit_depth > 8)
@@ -3179,8 +3181,7 @@ png_image_read_colormapped(png_voidp argument)
            image->colormap_entries == 244 /* 216 + 1 + 27 */)
            break;

-         /* goto bad_output; */
-         /* FALL THROUGH */
+         goto bad_output;

      default:
      bad_output:
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,7 +1,7 @@

 /* pngrtran.c - transforms the data in a row for PNG readers
 *
- * Last changed in libpng 1.6.30 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -49,6 +49,7 @@ png_set_crc_action(png_structrp png_ptr, int crit_action, int ancil_action)
      case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
         png_warning(png_ptr,
             "Can't discard critical data on CRC error");
+         /* FALLTHROUGH */
      case PNG_CRC_ERROR_QUIT:                                /* Error/quit */

      case PNG_CRC_DEFAULT:
@@ -1253,7 +1254,7 @@ png_init_rgb_transformations(png_structrp png_ptr)
            default:

            case 8:
-               /* FALL THROUGH (Already 8 bits) */
+               /* FALLTHROUGH */ /*  (Already 8 bits) */

            case 16:
               /* Already a full 16 bits */
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,7 +1,7 @@

 /* pngrutil.c - utilities to read a PNG file
 *
- * Last changed in libpng 1.6.30 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -2978,7 +2978,7 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
         case 2:
            png_ptr->user_chunk_cache_max = 1;
            png_chunk_benign_error(png_ptr, "no space in chunk cache");
-            /* FALL THROUGH */
+            /* FALLTHROUGH */
         case 1:
            /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
             * chunk being skipped, now there will be a hard error below.
@@ -2987,7 +2987,7 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,

         default: /* not at limit */
            --(png_ptr->user_chunk_cache_max);
-            /* FALL THROUGH */
+            /* FALLTHROUGH */
         case 0: /* no limit */
 #  endif /* USER_LIMITS */
            /* Here when the limit isn't reached or when limits are compiled
--- a/pngset.c
+++ b/pngset.c
@@ -1,7 +1,7 @@

 /* pngset.c - storage of image information into info struct
 *
- * Last changed in libpng 1.6.30 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.30 [June 28, 2017]
 * Copyright (c) 1998-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
--- a/pngtest.c
+++ b/pngtest.c
@@ -2088,4 +2088,4 @@ main(void)
 #endif

 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_30beta03 Your_png_h_is_not_version_1_6_30beta03;
+typedef png_libpng_version_1_6_31beta04 Your_png_h_is_not_version_1_6_31beta04;
--- a/pngtrans.c
+++ b/pngtrans.c
@@ -1,7 +1,7 @@

 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
 *
- * Last changed in libpng 1.6.30 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.30 [June 28, 2017]
 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,8 +1,8 @@

 /* pngwrite.c - general routines to write a PNG file
 *
- * Last changed in libpng 1.6.26 [October 20, 2016]
- * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.31 [(PENDING RELEASE)]
+ * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@@ -1007,8 +1007,8 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
         case 5:
         case 6:
         case 7: png_app_error(png_ptr, "Unknown row filter for method 0");
-            /* FALL THROUGH */
 #endif /* WRITE_FILTER */
+            /* FALLTHROUGH */
         case PNG_FILTER_VALUE_NONE:
            png_ptr->do_filter = PNG_FILTER_NONE; break;

@@ -1875,7 +1875,7 @@ png_image_set_PLTE(png_image_write_control *display)
               tRNS[i] = entry[afirst ? 0 : 3];
               if (tRNS[i] < 255)
                  num_trans = i+1;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */
            case 3:
               palette[i].blue = entry[afirst + (2 ^ bgr)];
               palette[i].green = entry[afirst + 1];
@@ -1886,7 +1886,7 @@ png_image_set_PLTE(png_image_write_control *display)
               tRNS[i] = entry[1 ^ afirst];
               if (tRNS[i] < 255)
                  num_trans = i+1;
-               /* FALL THROUGH */
+               /* FALLTHROUGH */
            case 1:
               palette[i].blue = palette[i].red = palette[i].green =
                  entry[afirst];
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1003,7 +1003,8 @@ png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
               optimize_cmf(data, png_image_size(png_ptr));
 #endif

-         png_write_complete_chunk(png_ptr, png_IDAT, data, size);
+         if (size > 0)
+            png_write_complete_chunk(png_ptr, png_IDAT, data, size);
         png_ptr->mode |= PNG_HAVE_IDAT;

         png_ptr->zstream.next_out = data;
@@ -1049,7 +1050,8 @@ png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
            optimize_cmf(data, png_image_size(png_ptr));
 #endif

-         png_write_complete_chunk(png_ptr, png_IDAT, data, size);
+         if (size > 0)
+            png_write_complete_chunk(png_ptr, png_IDAT, data, size);
         png_ptr->zstream.avail_out = 0;
         png_ptr->zstream.next_out = NULL;
         png_ptr->mode |= PNG_HAVE_IDAT | PNG_AFTER_IDAT;
--- a/projects/vstudio/README.txt
+++ b/projects/vstudio/README.txt
@@ -1,7 +1,7 @@

 VisualStudio instructions

-libpng version 1.6.30beta03 - May 22, 2017
+libpng version 1.6.31beta04 - July 11, 2017

 Copyright (c) 2010,2013,2015 Glenn Randers-Pehrson

--- a/projects/vstudio/zlib.props
+++ b/projects/vstudio/zlib.props
@@ -2,7 +2,7 @@
 <!--
 * zlib.props - location of zlib source
 *
- * libpng version 1.6.30beta03 - May 22, 2017
+ * libpng version 1.6.31beta04 - July 11, 2017
 *
 * Copyright (c) 1998-2011 Glenn Randers-Pehrson
 *
--- a/scripts/README.txt
+++ b/scripts/README.txt
@@ -1,9 +1,11 @@

-Makefiles for  libpng version 1.6.30beta03 - May 22, 2017
+Makefiles for  libpng version 1.6.31beta04 - July 11, 2017

 pnglibconf.h.prebuilt       =>  Stores configuration settings
 makefile.linux    =>  Linux/ELF makefile
-                       (gcc, creates libpng16.so.16.1.6.30beta03)
+                       (gcc, creates libpng16.so.16.1.6.31beta04)
+ makefile.linux-opt=>  Linux/ELF makefile with hardware optimizations on
+                       (gcc, creates libpng16.so.16.1.6.31beta04)
 makefile.gcc      =>  Generic makefile (gcc, creates static libpng.a)
 makefile.knr      =>  Archaic UNIX Makefile that converts files with
                       ansi2knr (Requires ansi2knr.c from
@@ -33,12 +35,12 @@ pnglibconf.h.prebuilt       =>  Stores configuration settings
 makefile.os2      =>  OS/2 Makefile (gcc and emx, requires libpng.def)
 makefile.sco      =>  For SCO OSr5  ELF and Unixware 7 with Native cc
 makefile.sggcc    =>  Silicon Graphics (gcc,
-                       creates libpng16.so.16.1.6.30beta03)
+                       creates libpng16.so.16.1.6.31beta04)
 makefile.sgi      =>  Silicon Graphics IRIX makefile (cc, creates static lib)
 makefile.solaris  =>  Solaris 2.X makefile (gcc,
-                       creates libpng16.so.16.1.6.30beta03)
+                       creates libpng16.so.16.1.6.31beta04)
 makefile.so9      =>  Solaris 9 makefile (gcc,
-                       creates libpng16.so.16.1.6.30beta03)
+                       creates libpng16.so.16.1.6.31beta04)
 makefile.std      =>  Generic UNIX makefile (cc, creates static libpng.a)
 makefile.sunos    =>  Sun makefile
 makefile.32sunu   =>  Sun Ultra 32-bit makefile
--- a/scripts/def.c
+++ b/scripts/def.c
@@ -21,7 +21,7 @@ PNG_DFN "OS2 DESCRIPTION "PNG image compression library""
 PNG_DFN "OS2 CODE PRELOAD MOVEABLE DISCARDABLE"
 PNG_DFN ""
 PNG_DFN "EXPORTS"
-PNG_DFN ";Version 1.6.30beta03"
+PNG_DFN ";Version 1.6.31beta04"

 #define PNG_EXPORTA(ordinal, type, name, args, attributes)\
        PNG_DFN "@" SYMBOL_PREFIX "@@" name "@"
--- a/scripts/libpng-config-head.in
+++ b/scripts/libpng-config-head.in
@@ -11,7 +11,7 @@

 # Modeled after libxml-config.

-version=1.6.30beta03
+version=1.6.31beta04
 prefix=""
 libdir=""
 libs=""
--- a/scripts/libpng.pc.in
+++ b/scripts/libpng.pc.in
@@ -5,6 +5,6 @@ includedir=@includedir@/libpng16

 Name: libpng
 Description: Loads and saves PNG files
-Version: 1.6.30beta03
+Version: 1.6.31beta04
 Libs: -L${libdir} -lpng16
 Cflags: -I${includedir}
--- a/scripts/makefile.cegcc
+++ b/scripts/makefile.cegcc
@@ -23,7 +23,7 @@

 VERMAJ = 1
 VERMIN = 6
-VERMIC = 30
+VERMIC = 31
 VER = $(VERMAJ).$(VERMIN).$(VERMIC)
 NAME = libpng
 PACKAGE = $(NAME)-$(VER)
--- a/scripts/makefile.linux
+++ b/scripts/makefile.linux
@@ -10,7 +10,7 @@
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 30
+RELEASE = 31

 # Shared library names:
 LIBSO=$(LIBNAME).so
--- a/scripts/makefile.linux-opt
+++ b/scripts/makefile.linux-opt
@@ -0,0 +1,265 @@
+# makefile for libpng.a and libpng16.so on Linux ELF with gcc
+# Copyright (C) 1998,1999,2002,2006,2008,2010-2014,2017 Greg Roelofs and
+# Glenn Randers-Pehrson
+# Copyright (C) 1996,1997 Andreas Dilger
+#
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
+# Library name:
+LIBNAME = libpng16
+PNGMAJ = 16
+RELEASE = 31
+
+# Shared library names:
+LIBSO=$(LIBNAME).so
+LIBSOMAJ=$(LIBNAME).so.$(PNGMAJ)
+LIBSOREL=$(LIBSOMAJ).$(RELEASE)
+OLDSO=libpng.so
+
+# Utilities:
+AR_RC=ar rc
+CC=gcc
+MKDIR_P=mkdir -p
+LN_SF=ln -sf
+RANLIB=ranlib
+CP=cp
+RM_F=/bin/rm -f
+
+# where "make install" puts libpng16.a, libpng16.so*,
+# libpng16/png.h, libpng16/pngconf.h, and libpng16/pnglibconf.h
+# Prefix must be a full pathname.
+prefix=/usr/local
+exec_prefix=$(prefix)
+
+# Where the zlib library and include files are located.
+#ZLIBLIB=/usr/local/lib
+#ZLIBINC=/usr/local/include
+ZLIBLIB=../zlib
+ZLIBINC=../zlib
+
+ALIGN=
+# for i386:
+#ALIGN=-malign-loops=2 -malign-functions=2
+
+#WARNMORE=-Wwrite-strings -Wpointer-arith \
+#	-Wmissing-declarations -Wtraditional -Wcast-align \
+#	-Wstrict-prototypes -Wmissing-prototypes
+
+# for pgcc version 2.95.1, -O3 is buggy; don't use it.
+
+CPPFLAGS=-I$(ZLIBINC)
+CPPFLAGS += -DPNG_ARM_NEON
+CPPFLAGS += -DPNG_MIPS_MSA
+CPPFLAGS += -DPNG_INTEL_SSE
+CPPFLAGS += -DPNG_POWERPC_VSX
+CPPFLAGS+=-ansi -pedantic -Wextra -Wall -Wshadow -Wno-sign-conversion
+CPPFLAGS+=-W -Wall -Wconversion $(ALIGN)
+# CPPFLAGS+=$(WARNMORE)
+CFLAGS= -O3 -funroll-loops
+
+LDFLAGS=-L. -Wl,-rpath,. -L$(ZLIBLIB) -Wl,-rpath,$(ZLIBLIB) -lpng16 -lz -lm
+LDFLAGS_A=-L$(ZLIBLIB) -Wl,-rpath,$(ZLIBLIB) libpng.a -lz -lm
+
+INCPATH=$(prefix)/include
+LIBPATH=$(exec_prefix)/lib
+MANPATH=$(prefix)/man
+BINPATH=$(exec_prefix)/bin
+
+# override DESTDIR= on the make install command line to easily support
+# installing into a temporary location.  Example:
+#
+#    make install DESTDIR=/tmp/build/libpng
+#
+# If you're going to install into a temporary location
+# via DESTDIR, $(DESTDIR)$(prefix) must already exist before
+# you execute make install.
+DESTDIR=
+
+DB=$(DESTDIR)$(BINPATH)
+DI=$(DESTDIR)$(INCPATH)
+DL=$(DESTDIR)$(LIBPATH)
+DM=$(DESTDIR)$(MANPATH)
+
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
+OBJS =  png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
+	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
+	pngwtran.o pngmem.o pngerror.o pngpread.o \
+	arm/arm_init.o arm/filter_neon_intrinsics.o \
+	mips/mips_init.o mips/filter_msa_intrinsics.o \
+	intel/intel_init.o intel/filter_sse2_intrinsics.o\
+	powerpc/powerpc_init.o powerpc/filter_vsx_intrinsics.o
+
+OBJSDLL = $(OBJS:.o=.pic.o)
+
+.SUFFIXES:      .c .o .pic.o
+
+.c.o:
+	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
+
+.c.pic.o:
+	$(CC) -c $(CPPFLAGS) $(CFLAGS) -fPIC -o $@ $*.c
+
+all: libpng.a $(LIBSO) pngtest pngtest-static libpng.pc libpng-config
+
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
+	$(CP) $(PNGLIBCONF_H_PREBUILT) $@
+
+libpng.a: $(OBJS)
+	$(AR_RC) $@ $(OBJS)
+	$(RANLIB) $@
+
+libpng.pc:
+	cat scripts/libpng.pc.in | sed -e s!@prefix@!$(prefix)! \
+	-e s!@exec_prefix@!$(exec_prefix)! \
+	-e s!@libdir@!$(LIBPATH)! \
+	-e s!@includedir@!$(INCPATH)! \
+	-e s!-lpng16!-lpng16\ -lz\ -lm! > libpng.pc
+
+libpng-config:
+	( cat scripts/libpng-config-head.in; \
+	echo prefix=\"$(prefix)\"; \
+	echo I_opts=\"-I$(INCPATH)/$(LIBNAME)\"; \
+	echo L_opts=\"-L$(LIBPATH)\"; \
+	echo R_opts=\"-Wl,-rpath,$(LIBPATH)\"; \
+	echo libs=\"-lpng16 -lz -lm\"; \
+	cat scripts/libpng-config-body.in ) > libpng-config
+	chmod +x libpng-config
+
+$(LIBSO): $(LIBSOMAJ)
+	$(LN_SF) $(LIBSOMAJ) $(LIBSO)
+
+$(LIBSOMAJ): $(OBJSDLL)
+	$(CC) -shared -Wl,-soname,$(LIBSOMAJ) -o $(LIBSOMAJ) $(OBJSDLL)
+
+pngtest: pngtest.o $(LIBSO)
+	$(CC) -o pngtest $(CFLAGS) pngtest.o $(LDFLAGS)
+
+pngtest-static: pngtest.o libpng.a
+	$(CC) -o pngtest-static $(CFLAGS) pngtest.o $(LDFLAGS_A)
+
+test: pngtest pngtest-static
+	@echo ""
+	@echo "   Running pngtest dynamically linked with $(LIBSO):"
+	@echo ""
+	./pngtest
+	@echo ""
+	@echo "   Running pngtest statically linked with libpng.a:"
+	@echo ""
+	./pngtest-static
+
+install-headers: png.h pngconf.h pnglibconf.h
+	-@if [ ! -d $(DI) ]; then $(MKDIR_P) $(DI); fi
+	-@if [ ! -d $(DI)/$(LIBNAME) ]; then $(MKDIR_P) $(DI)/$(LIBNAME); fi
+	cp png.h pngconf.h pnglibconf.h $(DI)/$(LIBNAME)
+	chmod 644 $(DI)/$(LIBNAME)/png.h $(DI)/$(LIBNAME)/pngconf.h $(DI)/$(LIBNAME)/pnglibconf.h
+	-@$(RM_F) $(DI)/png.h $(DI)/pngconf.h $(DI)/pnglibconf.h
+	-@$(RM_F) $(DI)/libpng
+	(cd $(DI); $(LN_SF) $(LIBNAME) libpng; $(LN_SF) $(LIBNAME)/* .)
+
+install-static: install-headers libpng.a
+	-@if [ ! -d $(DL) ]; then $(MKDIR_P) $(DL); fi
+	cp libpng.a $(DL)/$(LIBNAME).a
+	chmod 644 $(DL)/$(LIBNAME).a
+	-@$(RM_F) $(DL)/libpng.a
+	(cd $(DL); $(LN_SF) $(LIBNAME).a libpng.a)
+
+install-shared: install-headers $(LIBSOMAJ) libpng.pc
+	-@if [ ! -d $(DL) ]; then $(MKDIR_P) $(DL); fi
+	-@$(RM_F) $(DL)/$(LIBSO)
+	-@$(RM_F) $(DL)/$(LIBSOREL)
+	-@$(RM_F) $(DL)/$(OLDSO)
+	cp $(LIBSOMAJ) $(DL)/$(LIBSOREL)
+	chmod 755 $(DL)/$(LIBSOREL)
+	(cd $(DL); \
+	$(LN_SF) $(LIBSOREL) $(LIBSO); \
+	$(LN_SF) $(LIBSO) $(OLDSO))
+
+	-@if [ ! -d $(DL)/pkgconfig ]; then $(MKDIR_P) $(DL)/pkgconfig; fi
+	-@$(RM_F) $(DL)/pkgconfig/$(LIBNAME).pc
+	-@$(RM_F) $(DL)/pkgconfig/libpng.pc
+	cp libpng.pc $(DL)/pkgconfig/$(LIBNAME).pc
+	chmod 644 $(DL)/pkgconfig/$(LIBNAME).pc
+	(cd $(DL)/pkgconfig; $(LN_SF) $(LIBNAME).pc libpng.pc)
+
+install-man: libpng.3 libpngpf.3 png.5
+	-@if [ ! -d $(DM) ]; then $(MKDIR_P) $(DM); fi
+	-@if [ ! -d $(DM)/man3 ]; then $(MKDIR_P) $(DM)/man3; fi
+	-@$(RM_F) $(DM)/man3/libpng.3
+	-@$(RM_F) $(DM)/man3/libpngpf.3
+	cp libpng.3 $(DM)/man3
+	cp libpngpf.3 $(DM)/man3
+	-@if [ ! -d $(DM)/man5 ]; then $(MKDIR_P) $(DM)/man5; fi
+	-@$(RM_F) $(DM)/man5/png.5
+	cp png.5 $(DM)/man5
+
+install-config: libpng-config
+	-@if [ ! -d $(DB) ]; then $(MKDIR_P) $(DB); fi
+	-@$(RM_F) $(DB)/libpng-config
+	-@$(RM_F) $(DB)/$(LIBNAME)-config
+	cp libpng-config $(DB)/$(LIBNAME)-config
+	chmod 755 $(DB)/$(LIBNAME)-config
+	(cd $(DB); $(LN_SF) $(LIBNAME)-config libpng-config)
+
+install: install-static install-shared install-man install-config
+
+# If you installed in $(DESTDIR), test-installed won't work until you
+# move the library to its final location.  Use test-dd to test it
+# before then.
+
+test-dd:
+	echo
+	echo Testing installed dynamic shared library in $(DL).
+	$(CC) -I$(DI) $(CPPFLAGS) \
+	   `$(BINPATH)/$(LIBNAME)-config --cflags` pngtest.c \
+	   -L$(DL) -L$(ZLIBLIB) -Wl, -rpath,$(DL) -Wl,-rpath,$(ZLIBLIB) \
+	   -o pngtestd `$(BINPATH)/$(LIBNAME)-config --ldflags`
+	./pngtestd pngtest.png
+
+test-installed:
+	$(CC) $(CPPFLAGS) \
+	   `$(BINPATH)/$(LIBNAME)-config --cflags` pngtest.c \
+	   -L$(ZLIBLIB) -Wl,-rpath,$(ZLIBLIB) \
+	   -o pngtesti `$(BINPATH)/$(LIBNAME)-config --ldflags`
+	./pngtesti pngtest.png
+
+clean:
+	$(RM_F) *.o libpng.a pngtest pngout.png libpng-config \
+	$(LIBSO) $(LIBSOMAJ)* pngtest-static pngtesti \
+	libpng.pc pnglibconf.h
+
+DOCS = ANNOUNCE CHANGES INSTALL KNOWNBUG LICENSE README TODO Y2KINFO
+writelock:
+	chmod a-w *.[ch35] $(DOCS) scripts/*
+
+# DO NOT DELETE THIS LINE -- make depend depends on it.
+
+png.o png.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngerror.o pngerror.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngrio.o pngrio.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwio.o pngwio.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngmem.o pngmem.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngset.o pngset.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngget.o pngget.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngread.o pngread.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngrtran.o pngrtran.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngrutil.o pngrutil.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngtrans.o pngtrans.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwrite.o pngwrite.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwtran.o pngwtran.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwutil.o pngwutil.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngpread.o pngpread.pic.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+arm/arm_init.o arm/arm_init.o: pngpriv.h
+arm/filter_neon_intrinsics.o arm/filter_neon_intrinsics.pic.o: pngpriv.h
+mips/mips_init.o mips/mips_init.pic.o: pngpriv.h
+mips/filter_msa_intrinsics.o mips/filter_msa_intrinsics.pic.:  pngpriv.h
+intel/intel_init.o intel/intel_init.pic.:  pngpriv.h
+intel/filter_sse2_intrinsics.o intel/filter_sse2_intrinsics.pic.:  pngpriv.h
+powerpc/powerpc_init.o powerpc/powerpc_init.pic.:  pngpriv.h
+powerpc/filter_vsx_intrinsics.o powerpc/filter_vsx_intrinsics.pic.:  pngpriv.h
+
+pngtest.o: png.h pngconf.h pnglibconf.h
--- a/scripts/makefile.msys
+++ b/scripts/makefile.msys
@@ -18,7 +18,7 @@ exec_prefix=$(prefix)
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 30
+RELEASE = 31

 # Shared library names:
 LIBSO=$(LIBNAME).dll
--- a/scripts/makefile.ne12bsd
+++ b/scripts/makefile.ne12bsd
@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include/libpng16

 LIB=	png16
 SHLIB_MAJOR=	0
-SHLIB_MINOR=	1.6.30beta03
+SHLIB_MINOR=	1.6.31beta04
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
--- a/scripts/makefile.netbsd
+++ b/scripts/makefile.netbsd
@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include

 LIB=	png
 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.30beta03
+SHLIB_MINOR=	1.6.31beta04
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
--- a/scripts/makefile.openbsd
+++ b/scripts/makefile.openbsd
@@ -11,7 +11,7 @@ LIBDIR=	${PREFIX}/lib
 MANDIR= ${PREFIX}/man/cat

 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.30beta03
+SHLIB_MINOR=	1.6.31beta04

 LIB=	png
 SRCS=	png.c pngerror.c pngget.c pngmem.c pngpread.c \
--- a/scripts/pnglibconf.dfa
+++ b/scripts/pnglibconf.dfa
@@ -8,7 +8,7 @@ com pnglibconf.h - library build configuration
 com
 version
 com
-com Copyright (c) 1998-2016 Glenn Randers-Pehrson
+com Copyright (c) 1998-2017 Glenn Randers-Pehrson
 com
 com This code is released under the libpng license.
 com For conditions of distribution and use, see the disclaimer
--- a/scripts/pnglibconf.h.prebuilt
+++ b/scripts/pnglibconf.h.prebuilt
@@ -1,10 +1,10 @@
-/* libpng 1.6.30beta03 STANDARD API DEFINITION */
+/* libpng 1.6.31beta04 STANDARD API DEFINITION */

 /* pnglibconf.h - library build configuration */

-/* Libpng version 1.6.30beta03 - May 22, 2017 */
+/* Libpng version 1.6.31beta04 - July 11, 2017 */

-/* Copyright (c) 1998-2015 Glenn Randers-Pehrson */
+/* Copyright (c) 1998-2017 Glenn Randers-Pehrson */

 /* This code is released under the libpng license. */
 /* For conditions of distribution and use, see the disclaimer */
--- a/scripts/symbols.def
+++ b/scripts/symbols.def
@@ -1,4 +1,4 @@
-;Version 1.6.30beta03
+;Version 1.6.31beta04
 ;--------------------------------------------------------------
 ; LIBPNG symbol list as a Win32 DEF file
 ; Contains all the symbols that can be exported from libpng
Author	SHA1	Message	Date
Glenn Randers-Pehrson	f78a3e7326	[libpng16] Imported from libpng-1.6.31beta04.tar	2017-07-11 12:29:53 -05:00
John Bowler	72d07d3202	[libpng16] Removed one of the GCC-7.1.0 'strict-overflow' warnings that result when integers appear on both sides of a compare. Worked around the others by forcing the strict-overflow setting in the relevant functions to a level where they are not reported. Changed "FALL THROUGH" comments to "FALLTHROUGH" because GCC doesn't like the space. Worked around some C-style casts from (void*) because g++ 5.4.0 objects to them. Increased the buffer size for 'sprint' to pass the gcc 7.1.0 'sprint overflow' check that is on by default with -Wall -Wextra.	2017-07-11 08:47:05 -05:00
Glenn Randers-Pehrson	ecea632c4c	[libpng16] Cross-reference scripts/makefile.linux-opt in INSTALL	2017-07-09 19:35:10 -05:00
Glenn Randers-Pehrson	fd9c48fd9c	[libpng16]Fixed release numbering in makefile.linux,linux-opt, msys	2017-07-09 17:23:56 -05:00
Glenn Randers-Pehrson	f2621c5137	[libpng16] Bump version to 1.6.31beta04	2017-07-09 16:31:45 -05:00
Glenn Randers-Pehrson	a947052ec2	[libpng16] Imported from libpng-1.6.31beta03.tar	2017-07-09 16:31:25 -05:00
Glenn Randers-Pehrson	0a9d2719c5	[libpng16] Added scripts/makefile-linux-opt, which has hardware optimizations enabled.	2017-07-09 16:27:15 -05:00
Glenn Randers-Pehrson	aa6e0482fa	[libpng16] Quieted "declaration after statement" warnings in intel/filter_sse2.c.	2017-07-09 11:51:42 -05:00
Glenn Randers-Pehrson	77a063af16	[libpng16] Balance an if/endif pair in CMakeLists.txt	2017-07-09 08:28:03 -05:00
Glenn Randers-Pehrson	5cc23552a7	[libpng16]Change "int" to "png_uint_32" in intel/filter_sse2.c to prevent possible integer overflow (Bug report by John Bowler).	2017-07-09 08:26:54 -05:00
Glenn Randers-Pehrson	76b3a7e78f	[libpng16] Add "libpng_mips_sources" to CMakeLists.txt when building MIPS_MSA	2017-07-08 20:09:07 -05:00
Glenn Randers-Pehrson	2b80b401be	[libpng16] Mention cmake "PNG_HARDWARE_OPTIMIZATIONS" in INSTALL	2017-07-08 19:25:08 -05:00
Glenn Randers-Pehrson	f16c3406cd	[libpng16] Updated CMakeLists.txt to add INTEL_SSE and MIPS_MSA platforms.	2017-07-08 19:10:49 -05:00
Glenn Randers-Pehrson	918a6ac2b4	[libpng16] Bump version to 1.6.31beta03	2017-07-08 13:26:36 -05:00
Glenn Randers-Pehrson	bd5a826d37	[libpng16] Imported from libpng-1.6.31beta02.tar	2017-07-08 13:15:10 -05:00
Glenn Randers-Pehrson	50b6df5389	[libpng16] Added "--enable-hardware-optimizations" configuration flag to enable or disable all hardware optimizations with one flag. Send comments/corrections/commendations to png-mng-implement at lists.sf.net (subscription required; visit https://lists.sourceforge.net/lists/listinfo/png-mng-implement to subscribe) or to glennrp at users.sourceforge.net Glenn R-P	2017-07-08 12:59:23 -05:00
Glenn Randers-Pehrson	857ef82edf	[libpng16] Expand INSTALL instructions about enabling hardware optimizations.	2017-07-06 20:17:09 -05:00
Glenn Randers-Pehrson	f380ae5243	[libpng16] Added instructions for disabling hardware optimizations in INSTALL.	2017-07-05 19:20:57 -05:00
Glenn Randers-Pehrson	23b51990e3	[libpng16] Bump version to 1.6.31beta02	2017-07-05 06:46:10 -05:00
Glenn Randers-Pehrson	77417b8ea0	[libpng16] Imported from libpng-1.6.31beta01.tar	2017-07-05 06:45:46 -05:00
Glenn Randers-Pehrson	eed9efec4e	[libpng16] Added special case for FreeBSD in arm/filter_neon.S (Maya Rashish).	2017-07-05 05:36:59 -05:00
Glenn Randers-Pehrson	b5c16f8bfc	[libpng16] Added note about png_get_rowbytes() being affected by transforms	2017-07-03 11:11:44 -05:00
Glenn Randers-Pehrson	89b8c133e7	[libpng16] Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).	2017-07-03 10:08:31 -05:00
Glenn Randers-Pehrson	54126d5c59	[libpng16] Revised pngpriv.h to use PNG_VERSION_INFO_ONLY instead of PNG_ARM_NEON_IMPLEMENTATION == 2 to exclude some definitions that assembler cannot recognize.	2017-07-02 07:35:17 -05:00
Glenn Randers-Pehrson	660ce58597	[libpng16] Revised pngpriv.h to work around failure to compile arm/filter_neon.S ("typedef" directive is unrecognized by the assembler).	2017-07-01 16:29:42 -05:00
Glenn Randers-Pehrson	9f7134c3fc	[libpng16] Update some "last changed" dates	2017-06-29 17:52:18 -05:00
Glenn Randers-Pehrson	145361aaac	[libpng16] Bump version to 1.6.31beta01	2017-06-28 14:39:39 -05:00
Glenn Randers-Pehrson	58649f19cb	[libpng16] Imported from libpng-1.6.30.tar	2017-06-28 13:50:29 -05:00
Glenn Randers-Pehrson	14be73c8a3	[libpng16] Imported from libpng-1.6.30rc02.tar	2017-06-25 13:46:37 -05:00
Glenn Randers-Pehrson	87cd2dc07d	[libpng16] Imported from libpng-1.6.30rc01.tar	2017-06-14 10:11:47 -05:00
Glenn Randers-Pehrson	2d306c4b15	[libpng16] Bump version to 1.6.30beta05	2017-06-06 19:44:20 -05:00
Glenn Randers-Pehrson	5aaf6e889c	[libpng16] Imported from libpng-1.6.30beta04.tar	2017-06-06 19:38:17 -05:00
Glenn Randers-Pehrson	c548328904	[libpng16] Avoid writing an empty IDAT when the last IDAT exactly fills the compression buffer (bug report by Brian Baird). This bug was introduced in libpng-1.6.0.	2017-06-06 18:40:45 -05:00
Glenn Randers-Pehrson	11629b1c1a	[libpng16] Mention github issues and pull requests as a bug-reporting method.	2017-05-27 13:12:37 -05:00
Glenn Randers-Pehrson	774922da91	[libpng] Update GIT URL in documentation	2017-05-27 12:33:48 -05:00
Glenn Randers-Pehrson	7da2ea45b9	Merge branch 'ssl' of git://github.com/vszakats/libpng into libpng16 to update zlib.net URLs	2017-05-27 12:25:20 -05:00
Viktor Szakats	95f3c07d6f	use HTTPS for zlib.net	2017-05-27 13:54:30 +00:00
Glenn Randers-Pehrson	a315efe3b2	[libpng16] Mention CVE-2016-5737 in CHANGES, update intel "last changed" date	2017-05-24 09:58:09 -05:00
Glenn Randers-Pehrson	6155c6629d	[libpng16] Bump version to 1.6.30beta04	2017-05-22 10:03:26 -05:00