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Fix Windows atomic ops to return pre-operation value (match Linux/C11 semantics) #812

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Merged
ithewei merged 3 commits into from
Mar 11, 2026
Merged

Fix Windows atomic ops to return pre-operation value (match Linux/C11 semantics) #812

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dec4b90
Initial plan
Copilot Mar 10, 2026
de866ca
fix: use InterlockedExchangeAdd for Windows atomic ops to return old …
Copilot Mar 10, 2026
0f3ec91
fix: prefer GCC builtins over Interlocked for MinGW compatibility
Copilot Mar 11, 2026
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26 changes: 13 additions & 13 deletions base/hatomic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -44,30 +44,30 @@ typedef volatile size_t atomic_size_t;

typedef struct atomic_flag { atomic_long _Value; } atomic_flag;

#ifdef _WIN32
#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1))

#define ATOMIC_FLAG_TEST_AND_SET atomic_flag_test_and_set
static inline bool atomic_flag_test_and_set(atomic_flag* p) {
// return InterlockedIncrement((LONG*)&p->_Value, 1);
return InterlockedCompareExchange(&p->_Value, 1, 0);
return !__sync_bool_compare_and_swap(&p->_Value, 0, 1);
}

#define ATOMIC_ADD InterlockedAdd
#define ATOMIC_SUB(p, n) InterlockedAdd(p, -n)
#define ATOMIC_INC InterlockedIncrement
#define ATOMIC_DEC InterlockedDecrement
#define ATOMIC_ADD __sync_fetch_and_add
#define ATOMIC_SUB __sync_fetch_and_sub
#define ATOMIC_INC(p) ATOMIC_ADD(p, 1)
#define ATOMIC_DEC(p) ATOMIC_SUB(p, 1)

#elif __GNUC_PREREQ(4, 1)
#elif defined(_WIN32)

#define ATOMIC_FLAG_TEST_AND_SET atomic_flag_test_and_set
static inline bool atomic_flag_test_and_set(atomic_flag* p) {
return !__sync_bool_compare_and_swap(&p->_Value, 0, 1);
// return InterlockedIncrement((LONG*)&p->_Value, 1);
return InterlockedCompareExchange(&p->_Value, 1, 0);
}

#define ATOMIC_ADD __sync_fetch_and_add
#define ATOMIC_SUB __sync_fetch_and_sub
#define ATOMIC_INC(p) ATOMIC_ADD(p, 1)
#define ATOMIC_DEC(p) ATOMIC_SUB(p, 1)
#define ATOMIC_ADD InterlockedExchangeAdd
#define ATOMIC_SUB(p, n) InterlockedExchangeAdd(p, -(n))
#define ATOMIC_INC(p) InterlockedExchangeAdd(p, 1)
#define ATOMIC_DEC(p) InterlockedExchangeAdd(p, -1)

#endif

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