The memory debug helper stores the size of allocated blocks in a static variable when libxml2 is compiled with --with-mem-debug. The static vars are defined in xmlmemory.c as

static unsigned long  debugMemSize = 0;
static unsigned long  debugMemBlocks = 0;
static unsigned long  debugMaxMemSize = 0;

However the functions to retrieve the values return an int thus leading to an overflow when lots of memory is allocated

int
xmlMemUsed(void) {
     return(debugMemSize);
}

Also unsigned long isn't a wise choice since Windows always defines long as a 32bit type, even on AMD64 platform. This may lead to another overflow. size_t should be better.


recommended fix:

* use size_t instead of unsigned long

* either redefine the return type of xmlMemUsed() and xmlMemBlocks() or add two new methods like xmlMemUsedL() to return size_t.

While you are on it, a method xmlMemMaxUsed() wouldn't hurt, too. I can provide a patch if you concur with my analysis.