Port better to AIX.

* configure.ac (CFLAGS): Append -O if the user did not specify CFLAGS,
we did not already infer an optimization option, and -O works.
AIX xlc needs -O, otherwise garbage collection doesn't work.
* src/lisp.h (ENUM_BF) [__IBMC__]: Make it 'unsigned int' here, too,
to pacify AIX xlc.

Fixes: debbugs:14258

4 files changed, 39 insertions, 10 deletions

diff --git a/ChangeLog b/ChangeLog
index 5f74726a743..cf1d4f0d54e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2013-04-26  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Port better to AIX (Bug#14258).
+        * configure.ac (CFLAGS): Append -O if the user did not specify CFLAGS,
+        we did not already infer an optimization option, and -O works.
+        AIX xlc needs -O, otherwise garbage collection doesn't work.
+
 2013-04-22  Paul Eggert  <eggert@cs.ucla.edu>
 
         * make-dist: Do not distribute admin/unidata/Makefile.
diff --git a/configure.ac b/configure.ac
index 2b3afc1fb80..6c59dcaa7e3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -613,10 +613,10 @@ AC_DEFUN([gl_THREADLIB])
 dnl Amongst other things, this sets AR and ARFLAGS.
 gl_EARLY
 
-# It's helpful to have C macros available to GDB, so prefer -g3 to -g
-# if -g3 works and the user does not specify CFLAGS.
-# This test must follow gl_EARLY; otherwise AC_LINK_IFELSE complains.
 if test "$ac_test_CFLAGS" != set; then
+  # It's helpful to have C macros available to GDB, so prefer -g3 to -g
+  # if -g3 works and the user does not specify CFLAGS.
+  # This test must follow gl_EARLY; otherwise AC_LINK_IFELSE complains.
   case $CFLAGS in
     '-g')
       emacs_g3_CFLAGS='-g3';;
@@ -632,13 +632,29 @@ if test "$ac_test_CFLAGS" != set; then
       [emacs_cv_prog_cc_g3],
       [AC_LINK_IFELSE([AC_LANG_PROGRAM()],
          [emacs_cv_prog_cc_g3=yes],
-         [emacs_cv_prog_cc_g3=no])])
-    if test $emacs_cv_prog_cc_g3 = yes; then
-      CFLAGS=$emacs_g3_CFLAGS
-    else
+         [emacs_cv_prog_cc_g3=no])])
+    if test $emacs_cv_prog_cc_g3 != yes; then
       CFLAGS=$emacs_save_CFLAGS
     fi
   fi
+
+  case $CFLAGS in
+    *-O*) ;;
+    *)
+      # No optimization flag was inferred for this non-GCC compiler.
+      # Try -O.  This is needed for xlc on AIX; see Bug#14258.
+      emacs_save_CFLAGS=$CFLAGS
+      test -z "$CFLAGS" || CFLAGS="$CFLAGS "
+      CFLAGS=${CFLAGS}-O
+      AC_CACHE_CHECK([whether $CC accepts -O],
+        [emacs_cv_prog_cc_o],
+        [AC_LINK_IFELSE([AC_LANG_PROGRAM()],
+           [emacs_cv_prog_cc_o=yes],
+           [emacs_cv_prog_cc_o=no])])
+      if test $emacs_cv_prog_cc_o != yes; then
+        CFLAGS=$emacs_save_CFLAGS
+      fi ;;
+  esac
 fi
 
 AC_ARG_ENABLE([gcc-warnings],
diff --git a/src/ChangeLog b/src/ChangeLog
index 99e2c3d9a84..9ae5c29ab72 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2013-04-26  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Port better to AIX (Bug#14258).
+        * lisp.h (ENUM_BF) [__IBMC__]: Make it 'unsigned int' here, too,
+        to pacify AIX xlc.
+
 2013-04-24  Kenichi Handa  <handa@gnu.org>
 
         * coding.c (decode_coding_iso_2022): When an invalid escape
diff --git a/src/lisp.h b/src/lisp.h
index bcb866b4cc4..e2c24eed352 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -231,9 +231,9 @@ enum enum_USE_LSB_TAG { USE_LSB_TAG = 0 };
 #define case_Lisp_Int case Lisp_Int0: case Lisp_Int1
 #define LISP_INT_TAG_P(x) (((x) & ~Lisp_Int1) == 0)
 
-/* Stolen from GDB.  The only known compiler that doesn't support
-   enums in bitfields is MSVC.  */
-#ifdef _MSC_VER
+/* Idea stolen from GDB.  MSVC doesn't support enums in bitfields,
+   and xlc complains vociferously about them.  */
+#if defined _MSC_VER || defined __IBMC__
 #define ENUM_BF(TYPE) unsigned int
 #else
 #define ENUM_BF(TYPE) enum TYPE