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[libpng15] Update CHANGES and ANNOUNCE

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Glenn Randers-Pehrson 2016-12-26 19:28:24 -06:00
parent 80d36775d4
commit daa97ebf42
2 changed files with 40 additions and 0 deletions
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17
ANNOUNCE
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@ -34,6 +34,23 @@ version 1.5.28beta01 [December 27, 2016]
Added "Common linking failures" section to INSTALL.
Merge contrib/pngminim/*/makefile with libpng-1.6.24
Minor editing of INSTALL, (whitespace, added copyright line)
Removed the use of a macro containing the pre-processor 'defined'
operator. It is unclear whether this is valid; a macro that
"generates" 'defined' is not permitted, but the use of the word
"generates" within the C90 standard seems to imply more than simple
substitution of an expression itself containing a well-formed defined
operation.
Previously the pngtrans.c code always resulted in an unsigned arithmetic
overflow. This is well defined but produces errors from clang with the
option to detect unsigned overflow. As the expression only gets
evaluated once per row in this version of libpng it is easier just
to rewrite it.
The previous version of png.c produced a signed overflow as a result of
both the "& 0xffff" on the most significant bits of a negative argument;
this converted (-1) into 65535 which resulted in a subsequent overflow.
Since signed overflow is undefined in C90 the code has been modified to
correctly calculate a signed result. This requires changing the 'hi'
result parameter to a signed value.
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23
CHANGES
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@ -4504,6 +4504,29 @@ version 1.5.28beta01 [December 27, 2016]
Added "Common linking failures" section to INSTALL.
Merge contrib/pngminim/*/makefile with libpng-1.6.24
Minor editing of INSTALL, (whitespace, added copyright line)
Removed the use of a macro containing the pre-processor 'defined'
operator. It is unclear whether this is valid; a macro that
"generates" 'defined' is not permitted, but the use of the word
"generates" within the C90 standard seems to imply more than simple
substitution of an expression itself containing a well-formed defined
operation.
Previously the pngtrans.c code always resulted in an unsigned arithmetic
overflow. This is well defined but produces errors from clang with the
option to detect unsigned overflow. As the expression only gets
evaluated once per row in this version of libpng it is easier just
to rewrite it.
The previous version of png.c produced a signed overflow as a result of
both the "& 0xffff" on the most significant bits of a negative argument;
this converted (-1) into 65535 which resulted in a subsequent overflow.
Since signed overflow is undefined in C90 the code has been modified to
correctly calculate a signed result. This requires changing the 'hi'
result parameter to a signed value.
This has been code reviewed solely by the author. A further code review
is highly desireable. Nevertheless the code compiles without warnings
from clang and without the prior detection of an overflow. Since it no
longer truncates any of the intermediate values this should be enough to
ensure that it is correct.
Send comments/corrections/commendations to png-mng-implement at lists.sf.net
(subscription required; visit