Re: Zeroed pages returned for heap

[Ulrich Drepper]

On 6/6/05, Nagendra Singh Tomar <nagendra_tomar@xxxxxxxxxxx> wrote:
> Is it OK for an application (a C library implementing malloc/calloc is
> also an application) to assume that the pages returned by the OS for heap
> allocation (either directly thru brk() or thru mmap(MAP_ANONYMOUS)) will
> be zero filled.

The malloc code is glibc is defined with the assumption that brk
clears memory.  Since this is what the kernel implements it would be a
horrible waste of time to reinitialize the memory.  This behavior is
part of the kernel ABI and cannot be changed without breaking existing
applications without producing new libc DSOs (set MORECORE_CLEARS
appropriately) and relinking all statically linked apps.
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