Of Memory Management, Heap Corruption, and C++

Question

So, I need some help. I am working on a project in C++. However, I think I have somehow managed to corrupt my heap. This is based on the fact that I added an std::string to a class and assigning it a value from another std::string:

std::string hello = "Hello, world.\n";
/* exampleString = "Hello, world.\n" would work fine. */
exampleString = hello;

crashes on my system with a stack dump. So basically I need to stop and go through all my code and memory management stuff and find out where I've screwed up. The codebase is still small (about 1000 lines), so this is easily do-able.

Still, I'm over my head with this kind of stuff, so I thought I'd throw it out there. I'm on a Linux system and have poked around with valgrind, and while not knowing completely what I'm doing, it did report that the std::string's destructor was an invalid free. I have to admit to getting the term 'Heap Corruption' from a Google search; any general purpose articles on this sort of stuff would be appreciated as well.

(In before rm -rf ProjectDir, do again in C# :D)

EDIT: I haven't made it clear, but what I'm asking for are ways an advice of diagnosing these sort of memory problems. I know the std::string stuff is right, so it's something I've done (or a bug, but there's Not A Problem With Select). I'm sure I could check the code I've written up and you very smart folks would see the problem in no time, but I want to add this kind of code analysis to my 'toolbox', as it were.

Answer 1

These are relatively cheap mechanisms for possibly solving the problem:

1. Keep an eye on my heap corruption question - I'm updating with the answers as they shake out. The first was balancing new[] and delete[], but you're already doing that.
2. Give valgrind more of a go; it's an excellent tool, and I only wish it was available under Windows. I only slows your program down by about half, which is pretty good compared to the Windows equivalents.
3. Think about using the Google Performance Tools as a replacement malloc/new.
4. Have you cleaned out all your object files and started over? Perhaps your make file is... "suboptimal"
5. You're not assert()ing enough in your code. How do I know that without having seen it? Like flossing, no-one assert()s enough in their code. Add in a validation function for your objects and call that on method start and method end.
6. Are you compiling -wall? If not, do so.
7. Find yourself a lint tool like PC-Lint. A small app like yours might fit in the PC-lint demo page, meaning no purchase for you!
8. Check you're NULLing out pointers after deleteing them. Nobody likes a dangling pointer. Same gig with declared but unallocated pointers.
9. Stop using arrays. Use a vector instead.
10. Don't use raw pointers. Use a smart pointer. Don't use auto_ptr! That thing is... surprising; its semantics are very odd. Instead, choose one of the Boost smart pointers, or something out of the Loki library.