Messages in this thread | | | Date | Wed, 27 Jun 2007 00:11:38 -0400 | From | Rik van Riel <> | Subject | Re: [patch 2/3] MAP_NOZERO - implement sys_brk2() |
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Ulrich Drepper wrote: > On 6/26/07, Rik van Riel <riel@redhat.com> wrote: >> Since programs can get back free()d memory after a malloc(), >> with the old contents of the memory intact, surely your >> MAP_NONZERO behavior could be the default for programs that >> can get away with it? >> >> Maybe we could use some magic ELF header, similar to the >> way non-executable stack is handled? > > No. This is an implementation detail of the libc version. The malloc > as compiled today is expecting brk-ed memory to be zeroed. This > default can of course be changed (it's a simple define) but you cannot > make this the default behavior for brk.
After going through the first malloc()/free() cycle, surely the memory will no longer be zeroed on the second malloc() ?
What makes the first brk malloc so special?
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