Program only crashes as release build -- how to debug?


Question

I've got a "Schroedinger's Cat" type of problem here -- my program (actually the test suite for my program, but a program nonetheless) is crashing, but only when built in release mode, and only when launched from the command line. Through caveman debugging (ie, nasty printf() messages all over the place), I have determined the test method where the code is crashing, though unfortunately the actual crash seems to happen in some destructor, since the last trace messages I see are in other destructors which execute cleanly.

When I attempt to run this program inside of Visual Studio, it doesn't crash. Same goes when launching from WinDbg.exe. The crash only occurs when launching from the command line. This is happening under Windows Vista, btw, and unfortunately I don't have access to an XP machine right now to test on.

It would be really nice if I could get Windows to print out a stack trace, or something other than simply terminating the program as if it had exited cleanly. Does anyone have any advice as to how I could get some more meaningful information here and hopefully fix this bug?

Edit: The problem was indeed caused by an out-of-bounds array, which I describe more in this post. Thanks everybody for your help in finding this problem!

1
87
5/23/2017 11:33:14 AM

Accepted Answer

In 100% of the cases I've seen or heard of, where a C or C++ program runs fine in the debugger but fails when run outside, the cause has been writing past the end of a function local array. (The debugger puts more on the stack, so you're less likely to overwrite something important.)

120
10/9/2008 7:41:26 AM

When I have encountered problems like this before it has generally been due to variable initialization. In debug mode, variables and pointers get initialized to zero automatically but in release mode they do not. Therefore, if you have code like this

int* p;
....
if (p == 0) { // do stuff }

In debug mode the code in the if is not executed but in release mode p contains an undefined value, which is unlikely to be 0, so the code is executed often causing a crash.

I would check your code for uninitialized variables. This can also apply to the contents of arrays.


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