[libpng16] Start-up code size improvements, error handler flexibility. 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.
diff --git a/pngwio.c b/pngwio.c
index 8c1cab3..65ac856 100644
--- a/pngwio.c
+++ b/pngwio.c
@@ -34,7 +34,8 @@
{
/* NOTE: write_data_fn must not change the buffer! */
if (png_ptr->write_data_fn != NULL )
- (*(png_ptr->write_data_fn))(png_ptr, (png_bytep)data, length);
+ (*(png_ptr->write_data_fn))(png_ptr, png_constcast(png_bytep,data),
+ length);
else
png_error(png_ptr, "Call to NULL write function");