Added new "png_structrp" typedef. Because of the
way libpng works both png_info and png_struct are always accessed via a
single pointer. This means adding C99 'restrict' to the pointer gives
the compiler some opportunity to optimize the code. This change allows that.
Previously it was disabled whenever internal fixed point arithmetic was
selected, which meant it didn't exist even on systems where FP was available
but not preferred.
These changes alter how the tricky allocation of the initial png_struct and
png_info structures are handled. png_info is now handled in pretty much the
same way as everything else, except that the allocations handle NULL return
silently. png_struct is changed in a similar way on allocation and on
deallocation a 'safety' error handler is put in place (which should never
be required). The error handler itself is changed to permit mismatches
in the application and libpng error buffer size; however, this means a
silent change to the API to return the jmp_buf if the size doesn't match
the size from the libpng compilation; libpng now allocates the memory and
this may fail. Overall these changes result in slight code size
reductions; however, this is a reduction in code that is always executed
so is particularly valuable. Overall on a 64-bit system the libpng DLL
decreases in code size by 1733 bytes. pngerror.o increases in size by
about 465 bytes because of the new functionality.
of parallelism during 'make' the use of the same temporary file names such
as 'dfn*' can result in a race where a temporary file from one arm of the
build is deleted or overwritten in another arm. This changes the
temporary files for suffix rules to always use $* and ensures that the
non-suffix rules use unique file names.
Some compilers fault 'extern const' data declarations (because the data is
not initialized); this turns on const-ness only for compilers where
this is known to work.
using g++. The compiler imposes C++ rules on the C source; thus it
is desireable to make the source work with either C or C++ rules
without throwing away useful error information. This change adds
png_voidcast to allow C semantic (void*) cases or the corresponding
C++ static_cast operation, as appropriate.
The slightly modified tables reduce the number of 16-bit values that
convert to an off-by-one 8-bit value. The "makesRGB.c" code that was used
to generate the tables is now in a contrib/sRGBtables sub-directory.
