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[libpng16] Added information about configuring for multiprocessing to INSTALL.

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Glenn Randers-Pehrson 2014-03-16 19:31:09 -05:00
parent 2f5fb84cc4
commit 0464b436b6
1 changed files with 14 additions and 0 deletions
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INSTALL
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@ -395,6 +395,20 @@ pngusr.h a system builder may also define equivalent options in pngusr.dfa
(or, indeed, any file) and add that to the configuration by setting
DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate
how to do this, and a case where pngusr.h is still required.
Configuring libpng for multiprocessing
Libpng uses setjmp()/longjmp() for error handling. Unfortunately setjmp()
is known to be not thread-safe on some platforms and we don't know of
any platform where it is guaranteed to be thread-safe. Therefore, if
your application is going to be using multiple threads, you should
configure libpng with PNG_NO_SETJMP in your pngusr.dfa file, with
-DPNG_NO_SETJMP on your compile line, or with
#undef PNG_SETJMP_SUPPORTED
in your pnglibconf.h or pngusr.h.
Other sources of information about libpng:
Further information can be found in the README and libpng-manual.txt