Compiling gegl 0.1.4 on Solaris with gcc 3.4.6 fails with

  CC      exp-combine.c
exp-combine.c: In function `gegl_expcombine_new_exposure':
exp-combine.c:149: error: `NAN' undeclared (first use in this function)
exp-combine.c:149: error: (Each undeclared identifier is reported only once
exp-combine.c:149: error: for each function it appears in.)
exp-combine.c: In function `gegl_expcombine_normalize':

When adding "-std=c99 -D_XOPEN_SOURCE=600" to CFLAGS, compilation breaks at

 CC     gegl-xml.lo
gegl-xml.c:21:1: warning: "_XOPEN_SOURCE" redefined
<command line>:6:1: warning: this is the location of the previous definition
...
/usr/include/sys/feature_tests.h:332:2: #error "Compiler or options invalid for pre-UNIX 03 X/Open applications         and pre-2001 POSIX applications"

because gegl-xml.c contains

/* For clang, remove when getting rid of using PATH_MAX */
#define _XOPEN_SOURCE 500

This is probably another reason to evaluate Bug 617416 and the proposed patch.