Compilation Errors on Mac

I run ./configure and I receive the following errors amongst many warnings:

gcc -c -DLOCALEDIR=\"/usr/local/share/locale\" -DLOCALE_ALIAS_PATH=\"/usr/local/share/locale\" -DLIBDIR=\"/usr/local/lib\" -DBUILDING_LIBINTL -DBUILDING_DLL -DIN_LIBINTL -DENABLE_RELOCATABLE=1 -DIN_LIBRARY -DINSTALLDIR=\"/usr/local/lib\" -DNO_XMALLOC -Dset_relocation_prefix=libintl_set_relocation_prefix -Drelocate=libintl_relocate -DDEPENDS_ON_LIBICONV=1 -DHAVE_CONFIG_H -I. -I. -I..  -g -O2 -Wall -W -Wmissing-prototypes -Wstrict-prototypes -pedantic   xsize.c
In file included from xsize.c:3:
./xsize.h:56:1: error: unknown type name '_GL_UNUSED'
XSIZE_INLINE size_t

In file included from xsize.c:3:
./xsize.h:58:27: error: expected ';' after top level declarator

2 errors generated.
make[2]: *** [xsize.o] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2

Now, I also had similar issues compiling the older version over on SourceForge on my Mac. I wonder if my version of the gcc is too old?

$ which gcc
/usr/bin/gcc

$ gcc -v
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/c++/4.2.1
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.2.0
Thread model: posix

Do you know if there is a minimum version of gcc required for this to compile?

rrthomas / plptools

Compilation Errors on Mac #3