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From: Vicente Bergas <vicencb@gmail.com>
To: musl@lists.openwall.com
Subject: calloc question about clearing allocated memory
Date: Mon, 26 Jun 2017 23:30:53 +0200	[thread overview]
Message-ID: <CAAMcf8Bvw9Dwd177+WaQ+poArKfWuODPNC8DWsz55DYx3NdKQw@mail.gmail.com> (raw)

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.


             reply	other threads:[~2017-06-26 21:30 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-26 21:30 Vicente Bergas [this message]
2017-06-27 13:13 ` Szabolcs Nagy
2017-06-27 18:24   ` Vicente Bergas

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