-/* On at least Ultrix 4.3 and NextStep 3.2, getgroups (0, 0) always fails.
- On other systems, it returns the number of supplemental groups for the
- process. This function handles that special case and lets the system-
- provided function handle all others. */
+/* On OS X 10.6 and later, use the usual getgroups, not the one
+ supplied when _DARWIN_C_SOURCE is defined. _DARWIN_C_SOURCE is
+ normally defined, since it means "conform to POSIX, but add
+ non-POSIX extensions even if that violates the POSIX namespace
+ rules", which is what we normally want. But with getgroups there
+ is an inconsistency, and _DARWIN_C_SOURCE means "change getgroups()
+ so that it no longer works right". The BUGS section of compat(5)
+ says that the behavior is dubious if you compile different sections
+ of a program with different _DARWIN_C_SOURCE settings, so fix only
+ the offending symbol. */
+#ifdef __APPLE__
+int posix_getgroups (int, gid_t []) __asm ("_getgroups");
+# define getgroups posix_getgroups
+#endif
+
+/* On at least Ultrix 4.3 and NextStep 3.2, getgroups (0, NULL) always
+ fails. On other systems, it returns the number of supplemental
+ groups for the process. This function handles that special case
+ and lets the system-provided function handle all others. However,
+ it can fail with ENOMEM if memory is tight. It is unspecified
+ whether the effective group id is included in the list. */