_InterlockedDecrement Intrinsic Functions
Microsoft Specific
Provides compiler intrinsic support for the Win32 Windows SDK InterlockedDecrement function.
long _InterlockedDecrement(
long * lpAddend
);
long _InterlockedDecrement_acq(
long * lpAddend
);
long _InterlockedDecrement_rel(
long * lpAddend
);
long _InterlockedDecrement_nf(
long * lpAddend
);
short _InterlockedDecrement16(
short * lpAddend
);
short _InterlockedDecrement16_acq(
short * lpAddend
);
short _InterlockedDecrement16_rel(
short * lpAddend
);
short _InterlockedDecrement16_nf(
short * lpAddend
);
__int64 _InterlockedDecrement64(
__int64 * lpAddend
);
__int64 _InterlockedDecrement64_acq(
__int64 * lpAddend
);
__int64 _InterlockedDecrement64_rel(
__int64 * lpAddend
);
__int64 _InterlockedDecrement64_nf(
__int64 * lpAddend
);
Parameters
- [in, out] lpAddend
Pointer to the variable to be decremented.
Return Value
The return value is the resulting decremented value.
Requirements
Intrinsic |
Architecture |
|---|---|
_InterlockedDecrement, _InterlockedDecrement16, _InterlockedDecrement64 |
x86, ARM, x64 |
_InterlockedDecrement_acq, _InterlockedDecrement_rel, _InterlockedDecrement_nf, _InterlockedDecrement16_acq, _InterlockedDecrement16_rel, _InterlockedDecrement16_nf, _InterlockedDecrement64_acq, _InterlockedDecrement64_rel, _InterlockedDecrement64_nf, |
ARM |
Header file <intrin.h>
Remarks
There are several variations on _InterlockedDecrement that vary based on the data types they involve and whether processor-specific acquire or release semantics is used.
While the _InterlockedDecrement function operates on 32-bit integer values, _InterlockedDecrement16 operates on 16-bit integer values and _InterlockedDecrement64 operates on 64-bit integer values.
On ARM platforms, use the intrinsics with _acq and _rel suffixes if you need acquire and release semantics, such as at the beginning and end of a critical section. The intrinsics with an _nf ("no fence") suffix do not act as a memory barrier.
The variable pointed to by the lpAddend parameter must be aligned on a 32-bit boundary; otherwise, this function fails on multiprocessor x86 systems and any non-x86 systems. For more information, see align.
These routines are only available as intrinsics.
Example
// compiler_intrinsics_interlocked.cpp
// compile with: /Oi
#define _CRT_RAND_S
#include <cstdlib>
#include <cstdio>
#include <process.h>
#include <windows.h>
// To declare an interlocked function for use as an intrinsic,
// include intrin.h and put the function in a #pragma intrinsic
// statement.
#include <intrin.h>
#pragma intrinsic (_InterlockedIncrement)
// Data to protect with the interlocked functions.
volatile LONG data = 1;
void __cdecl SimpleThread(void* pParam);
const int THREAD_COUNT = 6;
int main() {
DWORD num;
HANDLE threads[THREAD_COUNT];
int args[THREAD_COUNT];
int i;
for (i = 0; i < THREAD_COUNT; i++) {
args[i] = i + 1;
threads[i] = reinterpret_cast<HANDLE>(_beginthread(SimpleThread, 0,
args + i));
if (threads[i] == reinterpret_cast<HANDLE>(-1))
// error creating threads
break;
}
WaitForMultipleObjects(i, threads, true, INFINITE);
}
// Code for our simple thread
void __cdecl SimpleThread(void* pParam) {
int threadNum = *((int*)pParam);
int counter;
unsigned int randomValue;
unsigned int time;
errno_t err = rand_s(&randomValue);
if (err == 0) {
time = (unsigned int) ((double) randomValue / (double) UINT_MAX * 500);
while (data < 100) {
if (data < 100) {
_InterlockedIncrement(&data);
printf_s("Thread %d: %d\n", threadNum, data);
}
Sleep(time); // wait up to half of a second
}
}
printf_s("Thread %d complete: %d\n", threadNum, data);
}