build: Use macOS' compatibility macros to enable all features.

* configure.ac: On macOS, use the compatibility macros to expose every
feature of the libc.  This is the equivalent of _GNU_SOURCE on GNU
libc.
--
Not defining this leads to compilation errors or superfluous warnings
on macOS.

GnuPG-bug-id: 2910
Signed-off-by: Justus Winter <justus@g10code.com>

diff --git a/configure.ac b/configure.ac
index 78508ec..2609b41 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -270,6 +270,10 @@ case "${host}" in
         ;;
     m68k-atari-mint)
         ;;
+    *-apple-darwin*)
+        AC_DEFINE(_DARWIN_C_SOURCE, 900000L,
+                  Expose all libc features (__DARWIN_C_FULL).)
+        ;;
     *)
       ;;
 esac