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src/Source/LibPNG/libpng-manual.txt  view on Meta::CPAN

    void user_error_fn(png_structp png_ptr,
        png_const_charp error_msg);

    void user_warning_fn(png_structp png_ptr,
        png_const_charp warning_msg);

The motivation behind using setjmp() and longjmp() is the C++ throw and
catch exception handling methods.  This makes the code much easier to write,
as there is no need to check every return code of every function call.
However, there are some uncertainties about the status of local variables
after a longjmp, so the user may want to be careful about doing anything
after setjmp returns non-zero besides returning itself.  Consult your
compiler documentation for more details.  For an alternative approach, you
may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net),
which is illustrated in pngvalid.c and in contrib/visupng.

Beginning in libpng-1.4.0, the png_set_benign_errors() API became available.
You can use this to handle certain errors (normally handled as errors)
as warnings.

src/Source/LibPNG/libpng.3  view on Meta::CPAN

    void user_error_fn(png_structp png_ptr,
        png_const_charp error_msg);

    void user_warning_fn(png_structp png_ptr,
        png_const_charp warning_msg);

The motivation behind using setjmp() and longjmp() is the C++ throw and
catch exception handling methods.  This makes the code much easier to write,
as there is no need to check every return code of every function call.
However, there are some uncertainties about the status of local variables
after a longjmp, so the user may want to be careful about doing anything
after setjmp returns non-zero besides returning itself.  Consult your
compiler documentation for more details.  For an alternative approach, you
may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net),
which is illustrated in pngvalid.c and in contrib/visupng.

Beginning in libpng-1.4.0, the png_set_benign_errors() API became available.
You can use this to handle certain errors (normally handled as errors)
as warnings.