c - Determining Stack Space with Visual Studio

Question

I'm programming in C in Visual Studio 2005. I have a multi-threaded program, but that's not especially important here.

How can I determine (approximately) how much stack space my threads use?

The technique I was planning to use is setting the stack memory to some predetermined value, say 0xDEADBEEF, running the program for a long time, pausing the program, and investigating the stack.

How do I read and write stack memory with Visual Studio?

EDIT: See, for example, "How to determine maximum stack usage." That question talks about an embedded system, but here I'm trying to determine the answer on a regular PC.

Answer 1

Windows does not commit the stack memory immediately; instead, it reserves the address space for it, and commits it page-by-page when it is accessed. Read this page for more info.

As a result, stack address space consists of three contiguous regions:

• Reserved but uncommitted memory which can be used for stack growth (but was never accessed yet);
• Guard page, which was never accessed yet too, and serves to trigger stack growth when accessed;
• Committed memory, i.e. stack memory which was ever accessed by the thread.

This allows us to construct a function that obtains stack size (with page size granularity):

static size_t GetStackUsage()
{
    MEMORY_BASIC_INFORMATION mbi;
    VirtualQuery(&mbi, &mbi, sizeof(mbi));
    // now mbi.AllocationBase = reserved stack memory base address

    VirtualQuery(mbi.AllocationBase, &mbi, sizeof(mbi));
    // now (mbi.BaseAddress, mbi.RegionSize) describe reserved (uncommitted) portion of the stack
    // skip it

    VirtualQuery((char*)mbi.BaseAddress + mbi.RegionSize, &mbi, sizeof(mbi));
    // now (mbi.BaseAddress, mbi.RegionSize) describe the guard page
    // skip it

    VirtualQuery((char*)mbi.BaseAddress + mbi.RegionSize, &mbi, sizeof(mbi));
    // now (mbi.BaseAddress, mbi.RegionSize) describe the committed (i.e. accessed) portion of the stack

    return mbi.RegionSize;
}

One thing to consider: CreateThread allows to specify initial stack commit size (via dwStackSize parameter, when STACK_SIZE_PARAM_IS_A_RESERVATION flag is not set). If this parameter is nonzero, our function will return correct value only when stack usage becomes greater than dwStackSize value.