Exactly How Does My C++ Program Terminate When it Runs Out of Memory?

Question

The following C++ program crashes on my Windows XP machine with a message "Abnormal program termination"

class Thing {};
int main()
{    
    for (;;) new Thing();    
}

I would say it's an out of memory problem, except I'm not sure Windows gets near the limit. Is it Windows killing it on purpose? If so, how does it decide?

Answer 1

Undoubtedly you are running out of VM.

Answer 2

Did you try to run it in debug?

In my case (Win7) it gave this error: This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information.

But in debug mode it showed that operator new threw excpetion bad_alloc which exactly mean out of memory.

Answer 3

You're right it's an out-of-memory problem that causes your program to end. But it's not Windows that decides to end it with "Abnormal program termination". It's the C++ runtime ("msvcrt*.dll" on Windows) that raises the std::bad_alloc exception when new Thing fails to allocate memory.

You can verify that with a simple change:

#include <exception>
#include <iostream>
class Thing {};
int main()
{
    try
    {    
        for (;;) new Thing();    
    }
    catch(std::bad_alloc e)
    {
        std::cout << "ending with bad_alloc" << std::endl;
    }        
}

This will end the program normally when the program is out of memory. If you don't catch that exception, the unhandled exception will be handled by the C++ runtime, thus creating that famous "Abnormal program termination" message (or something similar).

Answer 4

It is the CRT that is killing your program. The required behavior for an unhandled exception (std::bad_alloc here) is a call to terminate(). Which displays the "Abnormal program termination" message in the MSVC implementation and calls abort() to kill the program.