[MacPorts] #42571: libpng headers are invalid with older versions of clang

[MacPorts]

#42571: libpng headers are invalid with older versions of clang
------------------------+--------------------------
 Reporter:  jeremyhu@…  |      Owner:  ryandesign@…
     Type:  defect      |     Status:  new
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:  2.2.1
 Keywords:              |       Port:  libpng
------------------------+--------------------------
 https://sourceforge.net/p/libpng/bugs/220/

 {{{
 /opt/local/include/libpng16/pngconf.h:379:26: error: token is not a valid
 binary operator in a preprocessor subexpression
 if __has_extension(attribute_unavailable_with_message)
 }}}

 This occurred when building gimp2 using the version of clang in the Xcode
 3.2.6 for Snow Leopard:
 {{{
 $ /usr/bin/clang --version
 Apple clang version 1.7 (tags/Apple/clang-77) (based on LLVM 2.9svn)
 Target: x86_64-apple-darwin10
 Thread model: posix
 }}}


 For compatibility, please add:

 {{{
 #ifndef __has_extension
 #define __has_extension(x) 0
 #endif
 }}}

-- 
Ticket URL: <https://trac.macports.org/ticket/42571>
MacPorts <http://www.macports.org/>
Ports system for OS X