[MacPorts] #43939: libpng: pngconf.h:366:52: error: token is not a valid binary operator in a preprocessor subexpression (was: gegl @0.2.0_12: error: token is not a valid binary operator in a preprocessor subexpression)

[MacPorts]

#43939: libpng: pngconf.h:366:52: error: token is not a valid binary operator in a
preprocessor subexpression
-------------------------+--------------------------
  Reporter:  macports@…  |      Owner:  ryandesign@…
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.3.0
Resolution:              |   Keywords:
      Port:  libpng      |
-------------------------+--------------------------
Changes (by ryandesign@…):

 * cc: devans@… (added)
 * status:  new => assigned
 * port:  gegl => libpng
 * owner:  devans@… => ryandesign@…


Comment:

 Actually this is a libpng problem (the error message refers to a libpng
 header). We fixed a similar error encountered with the new libpng headers
 in #42571 some months ago. The problem only occurred with older versions
 of clang. On Snow Leopard, usually the very old version of clang provided
 by its version of Xcode would not be used, but gegl is unusual in that it
 blacklists all the other compilers. You should be able to work around this
 by installing a newer version of clang and using that to compile gegl, for
 example:

 {{{
 sudo port clean gegl
 sudo port install clang-3.4
 sudo port install gegl configure.compiler=macports-clang-3.4
 }}}

 I will need to contact the libpng developers to see how we can fix these
 headers to let older versions of clang process them correctly.

-- 
Ticket URL: <https://trac.macports.org/ticket/43939#comment:2>
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