Native stack overlapping system heap base address on some systems

Alexandre Julliard julliard at
Wed Mar 23 05:48:43 CST 2005

Mike Hearn <mh at> writes:

> I know people have been seeing this intermittently for a while now, we
> have a few CodeWeavers support tickets with this problem too. The issue
> seems to be that the Linux native (main thread) stack was allocated here:
>    7fffb000     20K rwx--    [ stack ]
> Surprise surprise, 0x7fffb000 + (1024 * 20) == 0x80000000
> Unfortunately I lack enough knowledge about the kernels VM algorithms to
> say why it's being allocated here. For comparison on my Fedora Core 3
> machine:
>    fef0d000     16K rwx--    [ stack ]
> One other thing I don't understand. It seems the stack and the system heap
> overlap by exactly 1 byte, otherwise the mmap would not fail.

No it doesn't overlap, a 20K mapping at 7fffb000 ends at
7fffffff. Most likely that kernel is configured for a 2Gb virtual
address space.

Alexandre Julliard
julliard at

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