[PATCH] autoconf: tune long long tests, particularly for c99

[Paul Eggert]

I pushed this.

---
 ChangeLog             |   16 ++++++++++
 lib/autoconf/types.m4 |   74 ++++++++++++++++++++++++++----------------------
 2 files changed, 56 insertions(+), 34 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index fbfbc53..79b9058 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2011-02-16  Paul Eggert  <address@hidden>
+
+       autoconf: tune long long tests, particularly for c99
+
+       This change is imported from gnulib.
+       * lib/autoconf/types.m4 (AC_TYPE_LONG_LONG_INT): Don't bother compiling
+       or running anything if c99, or if unsigned long long int does not
+       work.  In either case, we know the answer without further tests.
+       Do not compile _AC_TYPE_LONG_LONG_SNIPPET twice.  Instead, compile
+       it at most once, and use its results for both long long int and
+       unsigned long long int.  This is more likely to be efficient in
+       the common case where the program wants to check for both long
+       long int and unsigned long long int.
+       (AC_TYPE_UNSIGNED_LONG_LONG_INT): Don't bother compiling if c99,
+       since the answer is already known.
+
 2011-02-15  Eric Blake  <address@hidden>
 
        doc: fix debug advice typo
diff --git a/lib/autoconf/types.m4 b/lib/autoconf/types.m4
index 6583cb0..166aeb5 100644
--- a/lib/autoconf/types.m4
+++ b/lib/autoconf/types.m4
@@ -500,37 +500,40 @@ AC_DEFUN([_AC_TYPE_LONG_LONG_SNIPPET],
 # ---------------------
 AC_DEFUN([AC_TYPE_LONG_LONG_INT],
 [
+  AC_REQUIRE([AC_TYPE_UNSIGNED_LONG_LONG_INT])
   AC_CACHE_CHECK([for long long int], [ac_cv_type_long_long_int],
-    [AC_LINK_IFELSE(
-       [_AC_TYPE_LONG_LONG_SNIPPET],
-       [dnl This catches a bug in Tandem NonStop Kernel (OSS) cc -O circa 2004.
-       dnl If cross compiling, assume the bug isn't important, since
-       dnl nobody cross compiles for this platform as far as we know.
-       AC_RUN_IFELSE(
-         [AC_LANG_PROGRAM(
-            address@hidden:@include <limits.h>
-              @%:@ifndef LLONG_MAX
-              @%:@ define HALF \
-                       (1LL << (sizeof (long long int) * CHAR_BIT - 2))
-              @%:@ define LLONG_MAX (HALF - 1 + HALF)
-              @%:@endif]],
-            [[long long int n = 1;
-              int i;
-              for (i = 0; ; i++)
-                {
-                  long long int m = n << i;
-                  if (m >> i != n)
-                    return 1;
-                  if (LLONG_MAX / 2 < m)
-                    break;
-                }
-              return 0;]])],
-         [ac_cv_type_long_long_int=yes],
-         [ac_cv_type_long_long_int=no],
-         [ac_cv_type_long_long_int=yes])],
-       [ac_cv_type_long_long_int=no])])
+     [ac_cv_type_long_long_int=yes
+      if test "x${ac_cv_prog_cc_c99-no}" = xno; then
+       ac_cv_type_long_long_int=$ac_cv_type_unsigned_long_long_int
+       if test $ac_cv_type_long_long_int = yes; then
+         dnl Catch a bug in Tandem NonStop Kernel (OSS) cc -O circa 2004.
+         dnl If cross compiling, assume the bug is not important, since
+         dnl nobody cross compiles for this platform as far as we know.
+         AC_RUN_IFELSE(
+           [AC_LANG_PROGRAM(
+              address@hidden:@include <limits.h>
+                @%:@ifndef LLONG_MAX
+                @%:@ define HALF \
+                         (1LL << (sizeof (long long int) * CHAR_BIT - 2))
+                @%:@ define LLONG_MAX (HALF - 1 + HALF)
+                @%:@endif]],
+              [[long long int n = 1;
+                int i;
+                for (i = 0; ; i++)
+                  {
+                    long long int m = n << i;
+                    if (m >> i != n)
+                      return 1;
+                    if (LLONG_MAX / 2 < m)
+                      break;
+                  }
+                return 0;]])],
+           [],
+           [ac_cv_type_long_long_int=no])
+       fi
+      fi])
   if test $ac_cv_type_long_long_int = yes; then
-    AC_DEFINE([HAVE_LONG_LONG_INT], 1,
+    AC_DEFINE([HAVE_LONG_LONG_INT], [1],
       [Define to 1 if the system has the type `long long int'.])
   fi
 ])
@@ -542,12 +545,15 @@ AC_DEFUN([AC_TYPE_UNSIGNED_LONG_LONG_INT],
 [
   AC_CACHE_CHECK([for unsigned long long int],
     [ac_cv_type_unsigned_long_long_int],
-    [AC_LINK_IFELSE(
-       [_AC_TYPE_LONG_LONG_SNIPPET],
-       [ac_cv_type_unsigned_long_long_int=yes],
-       [ac_cv_type_unsigned_long_long_int=no])])
+    [ac_cv_type_unsigned_long_long_int=yes
+     if test "x${ac_cv_prog_cc_c99-no}" = xno; then
+       AC_LINK_IFELSE(
+        [_AC_TYPE_LONG_LONG_SNIPPET],
+        [],
+        [ac_cv_type_unsigned_long_long_int=no])
+     fi])
   if test $ac_cv_type_unsigned_long_long_int = yes; then
-    AC_DEFINE([HAVE_UNSIGNED_LONG_LONG_INT], 1,
+    AC_DEFINE([HAVE_UNSIGNED_LONG_LONG_INT], [1],
       [Define to 1 if the system has the type `unsigned long long int'.])
   fi
 ])
-- 
1.7.4