This adds a new configuration file, 'contrib/conftest/basic.dfa' which
disables unused APIs on a test Linux-based system. So support the
configuration several fixes were necessary in the test programs so that
the tests are skipped correctly when APIs are not available.
The configuration has been tested on a range of common Linux apps
including web browser code (qtwebengine), image processing code (e.g.
ImageMagick) and general display code (X11, Qt5 and Qt6, KDE). Overall
this first step reduces libpng linked code and data size to about 2/3 of
the full configuration.
To use the new test simply copy basic.dfa to 'pngusr.dfa' in the root of
the source directory and build.
Signed-off-by: John Bowler <jbowler@acm.org>
pngimage.c:
Initialize sig_bits on a NOTREACHED path to avoid warnings about using
uninitialized variables.
pngstest.c:
Enlarge buffers and fix signedness to avoid legitimate warnings about
potential buffer overflows.
pngunknown.c:
pngvalid.c:
Use NULL instead of 0 for pointers and apply other style fixes.
makepng.c:
tarith.c:
Apply various style fixes.
Also remove the "last changed" version info from source comments.
The version control system maintains this information automatically.
I got a warning while compiling under Ubuntu 18.04 and gcc 7.4:
"__BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
Quote from the Linux Programmer's Manual:
"To allow code that requires _BSD_SOURCE in glibc 2.19 and earlier and
_DEFAULT_SOURCE in glibc 2.20 and later to compile without warnings,
define both _BSD_SOURCE and _DEFAULT_SOURCE."
As per the const correctness rules, top-level const-ness of data
in automatic scopes does not propagate outside of these scopes
(unlike const-ness at lower levels, such as pointers to const data).
Previously, const was used liberally, but inconsistently across the
libpng codebase. Using const wherever applicable is not incorrect.
However, _consistent_ use of const is difficult to maintain in such
conditions.
In conclusion, we shall continue to use const only where doing so is
strictly necessary:
1. If a function guarantees that it will not modify an argument
passed by pointer, the corresponding function parameter should be
a pointer-to-const (const T *).
2. Static data should not be modified, therefore it should be const.
Reference:
Google C++ Style Guide
https://google.github.io/styleguide/cppguide.html#Use_of_const
In v1.6.0, size_t became a required type. It should be used
consistently. To maintain backwards compatibility, png_size_t
is still maintained in deprecated form.
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.
This removes the use of a macro containing the pre-processor 'defined'
operator. It is unclear whether this is valid; a macro which
"generates" 'defined' is not permitted, but the use of the work
"generates" within the C90 standard seems to imply more than simple
substitution of an expression itself containing a well-formed defined
operation.
Signed-off-by: John Bowler <jbowler@acm.org>
Remove all currently detected cases of unsigned overflow. Detection is
runtime, so test case dependent. The changes to pngvalid.c eliminate
spurious and probably invalid tests with one while loop exception.
Apart from that and the change to the dependence on the intended
unsigned overflow in pngtrans.c the changes are limited to altering the
meme for an unsigned 'x' from:
while (x-- > 0)
to
for (; x > 0; --x)
This works because, in all cases, the control variable is not used in
the loop. The 'while' meme was, at one time, warn'ed by GCC so it is
probably a good change, for some weird religious value of good.
Signed-off-by: John Bowler <jbowler@acm.org>
MSVC does not like (uInt) = -(unsigned) (i.e. as an initializer), but it is fine
with it if the conversion is explicitly invoked by a cast.
Signed-off-by: John Bowler <jbowler@acm.org>
Coverity rejects code where an array element count has type size_t, this
elminates the code in question from contrib/libtests/pngvalid.c
Signed-off-by: John Bowler <jbowler@acm.org>
The previous version of the code invariably passed just one byte at a time to
libpng. The intention was to pass a random number of bytes in the range 0..511
(and this is what happens now).
Signed-off-by: John Bowler <jbowler@acm.org>
Undefined because (png_byte) << shift is undefined if it changes the signed bit
(because png_byte is promoted to int). The libpng exported functions
png_get_uint_32 and png_get_uint_16 handle this.
Bug reported by David Drysdale as a result of reports from UBSAN in clang 3.8.
This changes pngvalid to use BE random numbers; this used to produce errors but
these should not be fixed as a result of the previous changes.
Signed-off-by: John Bowler <jbowler@acm.org>
This widens the 'limit' check on the internally calculated error limits in the
'DIGITIZE' case (the code used prior to 1.7 for rgb_to_gray error checks) and it
changes the check to only operate in non-release builds (base build type not RC
or RELEASE.)
Signed-off-by: John Bowler <jbowler@acm.org>
