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bpo-41617: check for bswap builtins before using #21942

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bpo-41617: check for bswap builtins before using #21942

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17 changes: 11 additions & 6 deletions Include/internal/pycore_bitutils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,9 +17,14 @@ extern "C" {
# error "this header requires Py_BUILD_CORE define"
#endif

#if defined(__clang__) || \
(defined(__GNUC__) && \
((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 8)))
// Don't break compilers that don't know about __has_builtin
#ifndef __has_builtin
# define __has_builtin(x) 0
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@vstinner vstinner Aug 24, 2020

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I dislike mocking this function. So I wrote a different fix: PR #21949.

#endif

// No check for clang here, __has_builtin is used instead
#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. */
Expand All @@ -34,7 +39,7 @@ extern "C" {
static inline uint16_t
_Py_bswap16(uint16_t word)
{
#ifdef _PY_HAVE_BUILTIN_BSWAP
#if defined(_PY_HAVE_BUILTIN_BSWAP) || __has_builtin(__builtin_bswap16)
return __builtin_bswap16(word);
#elif defined(_MSC_VER)
Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned short));
Expand All @@ -49,7 +54,7 @@ _Py_bswap16(uint16_t word)
static inline uint32_t
_Py_bswap32(uint32_t word)
{
#ifdef _PY_HAVE_BUILTIN_BSWAP
#if defined(_PY_HAVE_BUILTIN_BSWAP) || __has_builtin(__builtin_bswap32)
return __builtin_bswap32(word);
#elif defined(_MSC_VER)
Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned long));
Expand All @@ -66,7 +71,7 @@ _Py_bswap32(uint32_t word)
static inline uint64_t
_Py_bswap64(uint64_t word)
{
#ifdef _PY_HAVE_BUILTIN_BSWAP
#if defined(_PY_HAVE_BUILTIN_BSWAP) || __has_builtin(__builtin_bswap64)
return __builtin_bswap64(word);
#elif defined(_MSC_VER)
return _byteswap_uint64(word);
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