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Date: Mon, 26 Jun 2017 23:30:53 +0200
From: Vicente Bergas <vicencb@...il.com>
To: musl@...ts.openwall.com
Subject: calloc question about clearing allocated memory

Hello,
when compiling a program against the musl libc and running it under
valgrind, then it reports lots of uninitialized value errors.
I have tracked them down to only two sources:
http://git.musl-libc.org/cgit/musl/tree/src/string/strlen.c?id=e6def544#n15
http://git.musl-libc.org/cgit/musl/tree/src/malloc/malloc.c?id=e6def544#n375

The first one about strlen is clearly an optimization everybody would
like to have, but the second one in __malloc0 is not that obvious.
Please, could that be explained: why is *z read just before being
cleared?
In fact it is counter-intuitive and looks like an overhead.
In case there is a reason for it, it would be nice to put an
explanatory comment there. Otherwise, that extra read could be
removed to make valgrind happy.

Regards,
  Vicenç.

P.S.: Please, CC me as I am not subscribed to the list.

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