tree ec9f75afcaa6c6cbb78086ca520fd4fce136ef87
parent 6cac43c974806cf5823eccc754f42d68b4a55b42
author Glenn Randers-Pehrson <glennrp at users.sourceforge.net> 1277774268 -0500
committer Glenn Randers-Pehrson <glennrp at users.sourceforge.net> 1277774397 -0500

[devel] Reverted changes to call png_longjmp in contrib/gregbook

where it is not appropriate.  If mainprog->jmpbuf is used by setjmp,
then png_longjmp cannot be used.
Reversed patch to remove error handler when the jmp_buf is stored in the
main program structure, not the png_struct.
The error handler is needed because the default handler in libpng will
always use the jmp_buf in the library control structure; this is never
set.  The gregbook code is a useful example because, even though it
uses setjmp/longjmp, it shows how error handling can be implemented
using control mechanisms not directly supported by libpng.  The
technique will work correctly with mechanisms such as Microsoft
Structure Exceptions or C++ exceptions (compiler willing - note that gcc
does not by default support interworking of C and C++ error handling.)