[英]How to pass integer to CreateThread()?
How to pass int parameter to CreateThread callback function? 如何将int参数传递给CreateThread回调函数? I try it:
我试试看:
DWORD WINAPI mHandler(LPVOID sId) {
...
arr[(int)sId]
...
}
int id=1;
CreateThread(NULL, NULL, mHandler, (LPVOID)id, NULL, NULL);
But I get warnings: 但我收到警告:
warning C4311: 'type cast' : pointer truncation from 'LPVOID' to 'int'
warning C4312: 'type cast' : conversion from 'int' to 'LPVOID' of greater size
Pass the address of the integer instead of its value: 传递整数的地址而不是其值:
// parameter on the heap to avoid possible threading bugs
int* id = new int(1);
CreateThread(NULL, NULL, mHandler, id, NULL, NULL);
DWORD WINAPI mHandler(LPVOID sId) {
// make a copy of the parameter for convenience
int id = *static_cast<int*>(sId);
delete sId;
// now do something with id
}
You can make this warning go away by using appropriate types. 您可以使用适当的类型使此警告消失。 In this case use INT_PTR or DWORD_PTR (or any other _PTR type) type instead of int (see Windows Data Types in MSDN).
在这种情况下,使用INT_PTR或DWORD_PTR(或任何其他_PTR类型)类型而不是int(请参阅MSDN中的Windows数据类型 )。
DWORD WINAPI mHandler(LPVOID p)
{
INT_PTR id=reinterpret_cast<INT_PTR>(p);
}
...
INT_PTR id = 123;
CreateThread(NULL, NULL, mHandler, reinterpret_cast<LPVOID>(id), NULL, NULL);
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