Can't run process by Filename if read from file

Question

LPCSTR      __FileName = "program.exe";   

void ProcessRun(LPCSTR pszExeName)
    {
        PROCESS_INFORMATION piProcInfoGPS;
        STARTUPINFO siStartupInfo;
        SECURITY_ATTRIBUTES saProcess, saThread;
        ZeroMemory(&siStartupInfo, sizeof(siStartupInfo));
        siStartupInfo.cb = sizeof(siStartupInfo);
        saProcess.nLength = sizeof(saProcess);
        saProcess.lpSecurityDescriptor = NULL;
        saProcess.bInheritHandle = true;
        saThread.nLength = sizeof(saThread);
        saThread.lpSecurityDescriptor = NULL;
        saThread.bInheritHandle = true;

        CreateProcess(NULL, (LPTSTR)pszExeName, &saProcess, &saThread, false, CREATE_DEFAULT_ERROR_MODE, NULL, NULL, &siStartupInfo, &piProcInfoGPS);

        __hProcess = piProcInfoGPS.hProcess;
        __ProcessID = piProcInfoGPS.dwProcessId;
    }

If I pass __FileName to the function the program will run. However, when I read the filename from my ini file

[Launcher]
FileName=program.exe


char INIValue[256];
GetPrivateProfileString("Launcher", "FileName", "nan.exe", INIValue, 256, ".\\BackgroundConfig.ini");

string temp(INIValue);
__FileName = temp.c_str();

And then try to pass the filename to the function, it doesn't run. What in the world is causing this? The file name is exactly the same.

Check your current directory, most likely the ini file is not being found. Check your return values and error codes. Use a debugger and see what value (if any) is being read from the file. There are lots of things you could try before asking on here. — Jonathan Potter, Dec 13 '14 at 13:43
@JonathanPotter Hello. The ini file is being found and read. I have checks for this. The value is correctly read, see http://i.imgur.com/tqv7w6T.png. If I simply comment out the read part and manually set the LPCSTR to "Nightcore.exe" the process will start, which I find weird. — Zute, Dec 13 '14 at 13:47
Is your second code snippet within the same function that is calling `ProcessRun`? I suspect your `string` might be getting destroyed before you call `ProcessRun` — wakjah, Dec 13 '14 at 13:48
@wakjah Hello. No it is not. But I am assigning the value to a non-local variable, so how does this create an issue? Never thought of testing but the received string in ProcessRun is indeed NULL. Why is this? — Zute, Dec 13 '14 at 13:56

score 2 · Accepted Answer · edited May 23 '17 at 10:26

You haven't shown enough code to be certain that this is the issue, but consider the following:

char * someString;

void foo()
{
    std::string str("whatever");
    doSomethingWithCharStar(str.c_str()); // fine: str's data has not been destroyed yet
    someString = str.c_str();
} // uh-oh, here the std::string's memory will be deleted

void bar()
{
    foo(); // sets someString
    doSomethingWithCharStar(someString); // by the time we get here, though, the memory pointed to by someString is freed
}

The code above invokes undefined behaviour (assuming doSomethingWithCharStar dereferences the pointer passed in). Instead of storing a char* as a global, you should store a std::string. Better yet, don't use a global at all:

std::string foo()
{
    return std::string("whatever");
}

void bar()
{
    std::string value(foo());
    doSomethingWithCharStar(value.c_str());
}

Note that the issue encountered in the first snippet above is essentially the same issue as when Returning a reference to a local variable.

Hello, thanks. My bad, I thought it would be okay if I passed str's data to another non-local variable. Making both variables non-local solved the problem. Thanks again. — Zute, Dec 13 '14 at 14:13

Can't run process by Filename if read from file

1 Answers1