How to verify memory usage

Question

I'd like to implement a C++ function (using WIN32 API) to get current memory usage of my process.

I checked code from this post How to determine CPU and memory consumption from inside a process? and implemented the function.

bool GetMemoryUsage( size_t& usageInBytes )
{
    PROCESS_MEMORY_COUNTERS_EX pmc;
    if ( GetProcessMemoryInfo(GetCurrentProcess(), (PROCESS_MEMORY_COUNTERS*) &pmc, sizeof(pmc)) )
    {
        usageInBytes = pmc.WorkingSetSize;
        return true;
    }
    else
    {
        return false;
    }
}

However, when I try to test it like that:

size_t initialMemoryUsage = 0;
GetMemoryUsage( initialMemoryUsage );

size_t use = 596;
void* memUsed = malloc( use );

size_t memoryUsage = 0;
GetMemoryUsage( memoryUsage );
assert( memoryUsage == initialMemoryUsage + 596 );

free( memUsed );

GetMemoryUsage( memoryUsage );
assert( memoryUsage == initialMemoryUsage );

It fails:

• If GetMemoryUsage uses pmc.WorkingSetSize, memoryUsage is greater than initialMemoryUsage by 12288 and freeing memory does not make it decrease
• If GetMemoryUsage uses pmc.PrivateUsage, memoryUsage and initialMemoryUsage are all equal, even after I allocated some memory

How can I implement GetMemoryUsage in an accurate and reliable way to have the test above pass?

Answer 1

Actually, I want to check at runtime that a specific function call not introduce any memory leak. I want to check that any memory allocated by the function was released. So I need to know at some point how many memory was allocated by new/malloc and not released yet.

Sorry, it just doesn't work that way.

 std::string foo()
 {
     return "hello";
 }

When this function returns, there may be a new std::string that didn't exist before. That doesn't indicate any leak.

You have expectations about how software works that just isn't how software works.

I think you would find it more fruitful to look at how programmers typically debug memory leaks. A very common mistake people make when asking for help solving a problem is that they come up with a way they think the problem should be solved and ask for help getting that way to work. That's what you're doing.

Instead, describe your actual problem in as much detail as possible and ask experts to suggest how they think you should solve it. They're more likely to suggest ways that will work.