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Asymmetry between __libc_memalign() and free() in dl-tls.c ?

From: Colin Smith
Subject: Asymmetry between __libc_memalign() and free() in dl-tls.c ?
Date: 24 Jun 2003 11:39:34 -0700

Dear glibc mavens,

I'm working on an application developed under glibc-2.2.2.  When I run
it with glibc-2.3.2 in its special "debug" mode, it reports a memory
corruption error.  In debug mode, the app defines the symbols malloc(),
free() etc.  In the malloc case, it calls __libc_malloc with in order to
implement guard zones on either end of the requested memory buffer.

I've tracked this down to sysdeps/generic/dl-tls.c: the thread manager
allocates a buffer of memory with __libc_memalign(), but frees it with

If only it would free the memory with __libc_free(), my app would be
fine, since memory obtained/freed this way avoids the guard zone code. 
Since the memory is being freed with free(), we think it must have been
obtained with malloc, and when we don't see the magic pattern in the
guard zones the app assumes memory has been trampled.

Do you agree that it would be better if __libc_ calls were matched up
here, or is there a subtlety I'm missing?


Colin Smith

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