SGI's C compiler is ANSI C by default in IRIX 4 and later. Use the
  '-cckr' option to compile K&R (traditional) C. You can do this most
  easily by setting the environment variable SGI_CC to "-cckr" or by
  editing the application's Makefile, often by adding "-cckr" to the
  CFLAGS variable.

  A related problem is that Makefiles generated by 'imake' most often
  use 'cc -cckr -prototypes'; missing or incorrect prototypes usually
  just generate pages of warnings but may cause an unrecoverable
  error.  You can often work around this by removing "-prototypes" from
  the line where it appears in the Makefile (not the Imakefile).