bpo-41617: Add _Py__has_builtin() macro (GH-23260) (GH-23262)
Fix building pycore_bitutils.h internal header on old clang version
without __builtin_bswap16() (ex: Xcode 4.6.3 on Mac OS X 10.7).
Add a new private _Py__has_builtin() macro to check for availability
of a preprocessor builtin function.
Co-Authored-By: Joshua Root <jmr@macports.org>
Co-authored-by: Joshua Root <jmr@macports.org>
(cherry picked from commit b3b98082c5431e77c64cab2c85525a804436b505)
diff --git a/Include/internal/pycore_byteswap.h b/Include/internal/pycore_byteswap.h
index 975e150..2b20fc6 100644
--- a/Include/internal/pycore_byteswap.h
+++ b/Include/internal/pycore_byteswap.h
@@ -15,12 +15,9 @@
# error "this header requires Py_BUILD_CORE define"
#endif
-#if ((defined(__GNUC__) \
- && ((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 8))) \
- || (defined(__clang__) \
- && (__clang_major__ >= 4 \
- || (__clang_major__ == 3 && __clang_minor__ >= 2))))
- /* __builtin_bswap16() is available since GCC 4.8 and clang 3.2,
+#if defined(__GNUC__) \
+ && ((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 8))
+ /* __builtin_bswap16() is available since GCC 4.8,
__builtin_bswap32() is available since GCC 4.3,
__builtin_bswap64() is available since GCC 4.3. */
# define _PY_HAVE_BUILTIN_BSWAP
@@ -34,7 +31,7 @@
static inline uint16_t
_Py_bswap16(uint16_t word)
{
-#ifdef _PY_HAVE_BUILTIN_BSWAP
+#if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap16)
return __builtin_bswap16(word);
#elif defined(_MSC_VER)
Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned short));
@@ -49,7 +46,7 @@
static inline uint32_t
_Py_bswap32(uint32_t word)
{
-#ifdef _PY_HAVE_BUILTIN_BSWAP
+#if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap32)
return __builtin_bswap32(word);
#elif defined(_MSC_VER)
Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned long));
@@ -66,7 +63,7 @@
static inline uint64_t
_Py_bswap64(uint64_t word)
{
-#ifdef _PY_HAVE_BUILTIN_BSWAP
+#if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap64)
return __builtin_bswap64(word);
#elif defined(_MSC_VER)
return _byteswap_uint64(word);
diff --git a/Include/pyport.h b/Include/pyport.h
index 6505af4..4bd4eb4 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -863,4 +863,16 @@
# define _Py_NO_RETURN
#endif
+
+// Preprocessor check for a builtin preprocessor function. Always return 0
+// if __has_builtin() macro is not defined.
+//
+// __has_builtin() is available on clang and GCC 10.
+#ifdef __has_builtin
+# define _Py__has_builtin(x) __has_builtin(x)
+#else
+# define _Py__has_builtin(x) 0
+#endif
+
+
#endif /* Py_PYPORT_H */
diff --git a/Misc/NEWS.d/next/Build/2020-11-13-15-04-53.bpo-41617.98_oaE.rst b/Misc/NEWS.d/next/Build/2020-11-13-15-04-53.bpo-41617.98_oaE.rst
new file mode 100644
index 0000000..a5f35b2
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2020-11-13-15-04-53.bpo-41617.98_oaE.rst
@@ -0,0 +1,3 @@
+Fix building ``pycore_bitutils.h`` internal header on old clang version
+without ``__builtin_bswap16()`` (ex: Xcode 4.6.3 on Mac OS X 10.7). Patch by
+Joshua Root and Victor Stinner.