Make stdatomic.h work with gcc4.6 host compiler

This is needed to make L work correctly, and bionic tests pass
again, after applying the equivalent of
commit 00aaea364501b3b0abe58dae461136159df1e356 there.

It makes the preexisting code that uses __sync implementations
much more useful, although we should no longer be exercising that
code in AOSP.

Specifically fixes:

We were invoking __has_extension and __has_builtin for GCC compilations.
They're clang specific. Restructured the tests.

The __sync implementation was not defining the LOCK_FREE macros.

ATOMIC_VAR_INIT was using named field initializations.  These are a
C, not C++, feature, that is not supported by g++ 4.6.

The stdatomic bionic test still failed with 4.6 and glibc with our
questionable LOCK_FREE macro implementation.  Don't run that piece
with 4.6.

In L, this is a prerequisite for fixing:

    Bug:16880454
    Bug:16513433

Change-Id: I9b61e42307f96a114dce7552b6ead4ad1c544eab
(cherry picked from commit 32429606bf696d3b2ca555f132a0d60c566d0bd0)

1 files changed, 4 insertions, 1 deletions

diff --git a/tests/stdatomic_test.cpp b/tests/stdatomic_test.cpp
index 222bd9c..b7fb19b 100644
--- a/tests/stdatomic_test.cpp
+++ b/tests/stdatomic_test.cpp
@@ -63,14 +63,17 @@ TEST(stdatomic, atomic_signal_fence) {
 
 TEST(stdatomic, atomic_is_lock_free) {
   atomic_char small;
-  atomic_intmax_t big;
   ASSERT_TRUE(atomic_is_lock_free(&small));
+#if defined(__clang__) || __GNUC_PREREQ(4, 7)
+  // Otherwise stdatomic.h doesn't handle this.
+  atomic_intmax_t big;
   // atomic_intmax_t(size = 64) is not lock free on mips32.
 #if defined(__mips__) && !defined(__LP64__)
   ASSERT_FALSE(atomic_is_lock_free(&big));
 #else
   ASSERT_TRUE(atomic_is_lock_free(&big));
 #endif
+#endif
 }
 
 TEST(stdatomic, atomic_flag) {