The following patches are required to make pkg-config compile under IRIX:

--- parse.c.orig        2002-09-26 19:25:41.000000000 +0200
+++ parse.c
@@ -953,6 +953,7 @@ parse_package_file (const char *path)
     verbose_error ("Package file '%s' appears to be empty\n",
                    path);

+  fclose(f);
   return pkg;
 }

--- pkg.h.orig  2004-09-04 17:42:52.000000000 -0400
+++ pkg.h       2004-09-04 17:45:38.000000000 -0400
@@ -85,6 +85,7 @@
 char *   packages_get_I_cflags    (GSList     *pkgs);
 char *   package_get_other_cflags (Package    *pkg);
 char *   packages_get_all_cflags  (GSList     *pkgs);
+char *   packages_get_other_cflags(GSList     *pkgs);
 char *   package_get_var          (Package    *pkg,
                                    const char *var);
 char *   packages_get_var          (GSList     *pkgs,