Re: [GD-General] memory checking

[brian s. <pud...@po...>]

You can probably get what you need writing your own - I imagine that's 
what most cross-platform and console people end up doing.  It's what I 
did.  It's easy.

Assuming you have all the C allocation functions inside your own 
wrappers, you adjust all allocations to allocate a larger block, add 
guard bytes at the start and end of the block, and return a pointer to 
the inside of the block (you'll want to add enough bytes at the front to 
guarantee the same alignment that your platform's malloc delivers).  
You'll want to put a reference to the source file and line in that 
header block too, so you can see where the trashed pointer comes from.

Then when the pointer's freed, you just check those guard bytes and see 
if they're trashed, before calling the actual free function (with the 
pointer adjusted downward, of course). 

You can also keep a list of all the pointers you've alloc'ed, and write 
a function that walks over all of them looking for damage.  And if you 
have a list of all outstanding pointers, with file/line pairs, you can 
even start checking for leaks, if you're so inclined :)

You can do fancier stuff on Win32 and Xbox, like putting allocations in 
separate pages and using page protections to detect overruns 
immediately.  BoundsChecker probably does that (along with all sorts of 
other stuff).  But it's usually enough to be able to see which pointer 
got nuked.  If it's reproducible, you can watch a particular address in 
the debugger to see when it gets hit.

Hope this helps,

--brian

Brett Bibby wrote:

>I recently ran into a serious memory bug I just can't track down and it seems it's time to get some sort of memory debugging tool. Ideally it would be available for Win32, PS2 and GameCube and work with CodeWarrior, but just Windows would be acceptable.  The only tools I can find so far are BoundsChecker and Purify, but neither looks like it will work with our CodeWarrior setup.  I also tried just using the crtdbg funcitons, but getting the MS libs into CodeWarrior is proving problematic.
>
>Does anybody know of any commercial product that might be useful? Are there any standalone memory checkers out there? Anybody using BoundsChecker that can comment on whether you must have Visual Studio or not?
>
>Thanks,
>Brett
>
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