Portability: check 64-bit GNU atomic operators are useable

Sometimes (namely 32-bit OpenBSD libstdc++) do not fully implement the
GNU atomic operators for both 32-bit and 64-bit. But Squid makes use of
both types if the compiler deems them required.

We need to check them all before declaring the atomics usable, or not.

 Thanks to Stuart Henderson for identifying the issue.

diff --git a/configure.ac b/configure.ac
index 5b43401b5ba043d1222ea1eced983b3eece768e4..6f1b55de0d6af1dc87728bf1d17633097c8b7be4 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -424,17 +424,30 @@ dnl Check for atomic operations support in the compiler
 dnl
 AC_MSG_CHECKING([for GNU atomic operations support])
 AC_RUN_IFELSE([AC_LANG_PROGRAM([[
-    int n = 0;
+    int32_t n_32 = 0;
+    uint64_t n_64 = 0;
 ]],[[
-    __sync_add_and_fetch(&n, 10); // n becomes 10
-    __sync_fetch_and_add(&n, 20); // n becomes 30
-    __sync_sub_and_fetch(&n, 15); // n becomes 15
-    __sync_bool_compare_and_swap(&n, 15, 201); // n becomes 201
-    __sync_fetch_and_and(&n, 200); // n becomes 200
-    return (n == 200) ? 0 : -1;
+    // 32-bit
+    __sync_add_and_fetch(&n_32, 10); // n becomes 10
+    __sync_fetch_and_add(&n_32, 20); // n becomes 30
+    __sync_sub_and_fetch(&n_32, 15); // n becomes 15
+    __sync_bool_compare_and_swap(&n_32, 15, 201); // n becomes 201
+    __sync_fetch_and_and(&n_32, 200); // n becomes 200
+    if (n != 200) return -1;
+
+    // 64-bit
+    __sync_add_and_fetch(&n_64, 10); // n becomes 10
+    __sync_fetch_and_add(&n_64, 20); // n becomes 30
+    __sync_sub_and_fetch(&n_64, 15); // n becomes 15
+    __sync_bool_compare_and_swap(&n_64, 15, 201); // n becomes 201
+    __sync_fetch_and_and(&n_64, 200); // n becomes 200
+    if (n_64 != 200) return -1;
+
+    // seems to be okay.
+    return 0;
 ]])],
 [
-    AC_DEFINE(HAVE_ATOMIC_OPS,1,[Define to 1 if you have __sync_add_and_fetch() and such])
+    AC_DEFINE(HAVE_ATOMIC_OPS,1,[Define to 1 if you have GCC __sync_add_and_fetch() and such])
     AC_MSG_RESULT(yes)
 ],[
     AC_MSG_RESULT(no)