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
diff --git a/libc/include/stdatomic.h b/libc/include/stdatomic.h
index 47b333c..3db25a7 100644
--- a/libc/include/stdatomic.h
+++ b/libc/include/stdatomic.h
@@ -32,8 +32,20 @@
#include <sys/cdefs.h>
-#if defined(__cplusplus) && defined(_USING_LIBCXX) && \
- (__has_feature(cxx_atomic) || _GNUC_VER >= 407)
+
+#if defined(__cplusplus) && defined(_USING_LIBCXX)
+# ifdef __clang__
+# if __has_feature(cxx_atomic)
+# define _STDATOMIC_HAVE_ATOMIC
+# endif
+# else /* gcc */
+# if __GNUC_PREREQ(4, 7)
+# define _STDATOMIC_HAVE_ATOMIC
+# endif
+# endif
+#endif
+
+#ifdef _STDATOMIC_HAVE_ATOMIC
/* We have a usable C++ <atomic>; use it instead. */
@@ -46,6 +58,7 @@
/* included. The definitions in <atomic> themselves see */
/* the old definition, as they should. */
/* Client code sees the following definition. */
+
#define _Atomic(t) std::atomic<t>
using std::atomic_is_lock_free;
@@ -136,14 +149,24 @@
# include <uchar.h> /* For char16_t and char32_t. */
#endif
-#if __has_extension(c_atomic) || __has_extension(cxx_atomic)
-#define __CLANG_ATOMICS
-#elif __GNUC_PREREQ(4, 7)
-#define __GNUC_ATOMICS
-#elif defined(__GNUC__)
-#define __SYNC_ATOMICS
+#ifdef __clang__
+# if __has_extension(c_atomic) || __has_extension(cxx_atomic)
+# define __CLANG_ATOMICS
+# else
+# error "stdatomic.h does not support your compiler"
+# endif
+# if __has_builtin(__sync_swap)
+# define __HAS_BUILTIN_SYNC_SWAP
+# endif
#else
-#error "stdatomic.h does not support your compiler"
+# if __GNUC_PREREQ(4, 7)
+# define __GNUC_ATOMICS
+# else
+# define __SYNC_ATOMICS
+# ifdef __cplusplus
+# define __ATOMICS_AVOID_DOT_INIT
+# endif
+# endif
#endif
/*
@@ -152,33 +175,53 @@
#ifdef __GCC_ATOMIC_BOOL_LOCK_FREE
#define ATOMIC_BOOL_LOCK_FREE __GCC_ATOMIC_BOOL_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_BOOL_LOCK_FREE 2 /* For all modern platforms */
#endif
#ifdef __GCC_ATOMIC_CHAR_LOCK_FREE
#define ATOMIC_CHAR_LOCK_FREE __GCC_ATOMIC_CHAR_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_CHAR_LOCK_FREE 2
#endif
#ifdef __GCC_ATOMIC_CHAR16_T_LOCK_FREE
#define ATOMIC_CHAR16_T_LOCK_FREE __GCC_ATOMIC_CHAR16_T_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_CHAR16_T_LOCK_FREE 2
#endif
#ifdef __GCC_ATOMIC_CHAR32_T_LOCK_FREE
#define ATOMIC_CHAR32_T_LOCK_FREE __GCC_ATOMIC_CHAR32_T_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_CHAR32_T_LOCK_FREE 2
#endif
#ifdef __GCC_ATOMIC_WCHAR_T_LOCK_FREE
#define ATOMIC_WCHAR_T_LOCK_FREE __GCC_ATOMIC_WCHAR_T_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_WCHAR_T_LOCK_FREE 2
#endif
#ifdef __GCC_ATOMIC_SHORT_LOCK_FREE
#define ATOMIC_SHORT_LOCK_FREE __GCC_ATOMIC_SHORT_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_SHORT_LOCK_FREE 2
#endif
#ifdef __GCC_ATOMIC_INT_LOCK_FREE
#define ATOMIC_INT_LOCK_FREE __GCC_ATOMIC_INT_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_INT_LOCK_FREE 2
#endif
#ifdef __GCC_ATOMIC_LONG_LOCK_FREE
#define ATOMIC_LONG_LOCK_FREE __GCC_ATOMIC_LONG_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_LONG_LOCK_FREE 2
#endif
#ifdef __GCC_ATOMIC_LLONG_LOCK_FREE
#define ATOMIC_LLONG_LOCK_FREE __GCC_ATOMIC_LLONG_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_LLONG_LOCK_FREE 1 /* maybe */
#endif
#ifdef __GCC_ATOMIC_POINTER_LOCK_FREE
#define ATOMIC_POINTER_LOCK_FREE __GCC_ATOMIC_POINTER_LOCK_FREE
+#elif defined(__SYNC_ATOMICS)
+#define ATOMIC_POINTER_LOCK_FREE 2
#endif
/*
@@ -189,7 +232,11 @@
#define ATOMIC_VAR_INIT(value) (value)
#define atomic_init(obj, value) __c11_atomic_init(obj, value)
#else
+#ifdef __ATOMICS_AVOID_DOT_INIT
+#define ATOMIC_VAR_INIT(value) { value }
+#else
#define ATOMIC_VAR_INIT(value) { .__val = (value) }
+#endif
#define atomic_init(obj, value) ((void)((obj)->__val = (value)))
#endif
@@ -289,7 +336,7 @@
* 7.17.6 Atomic integer types.
*/
-#if !__has_extension(c_atomic) && !__has_extension(cxx_atomic)
+#ifndef __CLANG_ATOMICS
/*
* No native support for _Atomic(). Place object in structure to prevent
* most forms of direct non-atomic access.
@@ -410,7 +457,7 @@
desired, success, failure) \
atomic_compare_exchange_strong_explicit(object, expected, \
desired, success, failure)
-#if __has_builtin(__sync_swap)
+#ifdef __HAS_BUILTIN_SYNC_SWAP
/* Clang provides a full-barrier atomic exchange - use it if available. */
#define atomic_exchange_explicit(object, desired, order) \
((void)(order), __sync_swap(&(object)->__val, desired))
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_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) {
