There is already a bug reported on this at www.sourceforge.org, but the developers declared it a Redhat bug. The getenv prototype in stdlib.h conflicts with a declaration in one of the gtk-- source files (parser.yy). There is a hack mentioned in the bug at sourceforge that gets the compilation to complete, but there's no guarentee that the hack produces valid code. http://sourceforge.net/bugs/?func=detailbug&bug_id=115781&group_id=1161 The actual text of the compile error can be found at the above link.
This is a plain-and-simple gtk-- bug. getenv() is defined to be declared in stdlib.h: http://www.opengroup.org/onlinepubs/007908799/xsh/getenv.html And prototype in parser.yy is just wrong - extern "C" only affects mangling and does not give the C interpretation of () - see Stroustrup's "The C++ Programming Language", section 9.2.4.
I suspected it was their bug, but apparently it compiles ok on Redhat6.2. I guess they'll have to own up to it eventually (when one of the developers installs Redhat7.0).