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Re: avoiding recursive calls of calloc due to optimization
- From: Andrew Pinski <pinskia at gmail dot com>
- To: Daniel Gutson <daniel dot gutson at tallertechnologies dot com>
- Cc: gcc Mailing List <gcc at gcc dot gnu dot org>, glisse at gcc dot gnu dot org, Sebastian Huber <sebastian dot huber at embedded-brains dot de>
- Date: Mon, 21 Sep 2015 10:26:23 -0700
- Subject: Re: avoiding recursive calls of calloc due to optimization
- Authentication-results: sourceware.org; auth=none
- References: <CAF5HaEWYyPpxQe_iJqF8LXn_Yp-8aJ6uzMP-nzK9Y5UhRX_JwQ at mail dot gmail dot com>
On Mon, Sep 21, 2015 at 10:20 AM, Daniel Gutson
> This is derived from https://gcc.gnu.org/ml/gcc-help/2015-03/msg00091.html
> Currently, gcc provides an optimization that transforms a call to
> malloc and a call to memset into a call to calloc.
> This is fine except when it takes place within the calloc() function
> implementation itself, causing a recursive call.
> Two alternatives have been proposed: -fno-malloc-builtin and disable
> optimizations in calloc().
> I think the former is suboptimal since it affects all the code just
> because of the implementation of one function (calloc()),
> whereas the latter is suboptimal too since it disables the
> optimizations in the whole function (calloc too).
> I think of two alternatives: either make -fno-calloc-builtin to
> disable the optimization, or make the optimization aware of the
> function context where it is operating and prevent it to do the
> transformation if the function is calloc().
> Please help me to find the best alternative so we can implent it.
Did you try the optimize attribute?
Also you can try the following:
size_t ns = size*elements;
If (ns / elements != size)
void *ptr = malloc (ns);
memset (ptr, 0, ns);
Notice I put in a check for overflow in there.