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POWhat causes a segfault in C++ STL list node memory allocation?
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copied!<p>I've written some C++ code that runs perfectly fine on my laptop PC (compiled under both a Microsoft compiler and g++ under MinGW). I am in the process of porting it to a Unix machine.</p> <p>I've compiled with both g++ and with Intel's ipcp on the Unix machine and in both cases, my program crashes (segfaults) after running for a while. I can run it for a short time without a crash. </p> <p>When I debug, I find that the crash is happening when the program tries to copy an STL list - specifically, it happens when the program tries to allocate memory to create a new node in the list. And the error I get in the debugger (TotalView) is that "an allocation call failed or the address returned is null."</p> <p>The crash does not always happen in the same place in the code each time I run it, but does always happen during an allocation call to create a node in an STL list. I don't think I'm running out of memory. I have a few memory leaks, but they're very small. What else can cause a memory allocation error? And why does it happen on the Unix machine and not on my PC? </p> <p>UPDATE: I used MemoryScape to help debug. When I used guard blocks, the program ran through without crashing, further suggesting a memory issue. What finally worked to nail down the problem was to "paint" allocated memory. It turns out I was initializing a variable, but not setting it to a value before I used it as an array index. The array was therefore overrunning because it was using whatever garbage was in the variable's memory location -- often it was 0 or some other small number, so no problem. But when I ran the program long enough, it was more likely to hold a larger number and corrupt the heap when I wrote out of bounds of the array. Painting the allocated memory with a large number forced a segfault right at the line of code where I attempted to write a value in the array and I could see that large painted number being used as the array index.</p>

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