Compilation fails due to -Wreturn-type errors

[DyniteMrc5]

Environment:

gcc --version Configured with: --prefix=/Applications/Xcode_6.4.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn) Target: x86_64-apple-darwin14.5.0 Thread model: posix

I get lots of errors about functions which don't declare a return type.

In order to fix it, I had to ./configure CC='gcc -Wno-return-type -std=gnu89'

(Also separate issues: I had to create directories lib and bin or the make failed)