进程ID函数得到错误“ ERROR_NO_MORE_FILES”

Question

Im trying to get the ID from a process using the function below, however GetLastError keeps returning ERROR_NO_MORE_FILES so it never gets the chance to iterate through all the processes. Im not sure whats causing this. Any ideas? Also as a test i was passing in the param as "notepad.exe"

int GetProcID(string ProcName){
    PROCESSENTRY32 PE32;
    HANDLE ProcSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS,0);

    PE32.dwSize = sizeof(PROCESSENTRY32);

    if(!Process32First(ProcSnapshot,&PE32))
        return 0;
    else
        if(PE32.szExeFile == ProcName)
            return PE32.th32ProcessID;
        else
        {
            while(GetLastError() != ERROR_NO_MORE_FILES){
                Process32Next(ProcSnapshot,&PE32);
                    if(PE32.szExeFile == ProcName)
                        return PE32.th32ProcessID;
            }
            return 0;
        }
}

Answer 1

Your while loop is wrong. You shouldn't be checking for the error value even before calling Process32Next function. Your function will return without doing anything if the prior call to a Windows API function (probably another Process32Next function) returned ERROR_NO_MORE_FILES , and the name of the first process in the snapshot happens to be something other than the name you want to search for.

Keep in mind that not all API functions set the error code to ERROR_SUCCESS even they have succeeded (and also don't forget to close the snapshot handle after you're done with it).