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Asked: 2026-06-09T12:32:57+00:00

Is it possible for stack space allocated by CreateThread to interfere with the usage

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Is it possible for stack space allocated by CreateThread to interfere with the usage of VirtualAlloc? I can’t find any discussion or documentation explaining precisely where stack space is allowed to be allocated…

The following more precisely illustrates my question:

uint8_t *baseA = (uint8_t*)VirtualAlloc(NULL,1,MEM_RESERVE,PAGE_NOACCESS);

// Create a thread with the default stack size
HANDLE hThread = CreateThread(NULL,0,SomeThreadProc,NULL,NULL,NULL);

// Possibly create even more threads here.

// Can this ever fail in the absence of other allocators? It doesn't here...
uint8_t *baseB = (uint8_t*)VirtualAlloc(NULL,1,MEM_RESERVE,PAGE_NOACCESS);

// Furthermore, in this test, baseB-baseA == 65536 (unless the debugger did something),
// so nothing appeared between baseA and baseB... not even enough space for the
// full 64kb of wastage, as baseA points to 4096 bytes by itself

If it does in fact use some analogue of VirtualAlloc, is there a way to change how Windows allocates stack space in a given process?

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1 Answer

  1. Editorial Team

    Stack space can be allocated anywhere in the address space of the process. There is no documentation on this now and it is unlikely that such documentation will appear in the future.

    You can safely assume that creation of the thread and virtual alloc are independent. If this would not be the case, a lot of things would be broken. Allocator cannot give out overlapping address ranges. This is unthinkable. The problem is somewhere else.

    The only thing that might look like correlation – amount of memory used and virtual address space fragmentation. In this case the latest request will simply fail.

    I worked on a memory analysis utilities.

    enter image description here

    This picture shows distribution of the numbers of virtual allocations per size of the allocation.

    enter image description here

    This is example of the address space contents for a 32-bit process (blue – committed, magenta – reserved, green is a free memory).

    What I write here is based on a real experience.

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