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Re: [PATCH] Fix unsafe function attributes for special functions (PR 71876)

From: Jeff Law <law at redhat dot com>
To: Bernd Edlinger <bernd dot edlinger at hotmail dot de>, Richard Biener <rguenther at suse dot de>
Cc: "jakub at redhat dot com" <jakub at redhat dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Jan Hubicka <hubicka at ucw dot cz>
Date: Wed, 20 Jul 2016 12:48:45 -0600
Subject: Re: [PATCH] Fix unsafe function attributes for special functions (PR 71876)
Authentication-results: sourceware.org; auth=none
References: <AM4PR0701MB216226C00439A01515A3AA5FE4370@AM4PR0701MB2162.eurprd07.prod.outlook.com> <alpine.LSU.2.11.1607201243320.30444@t29.fhfr.qr> <AM4PR0701MB2162738A0964E4579175FE86E4080@AM4PR0701MB2162.eurprd07.prod.outlook.com> <8ecb18e7-7914-aa9f-3000-95fd0830c2a5@redhat.com> <AM4PR0701MB2162F81DBC64692DC5100927E4080@AM4PR0701MB2162.eurprd07.prod.outlook.com>

On 07/20/2016 10:54 AM, Bernd Edlinger wrote:


Yes. That is another interesting observation.  I think, originally this
flag was introduced by Jan Hubicka, and should mean, "it may be alloca
or a weak alias to alloca or maybe even something different".
But some of the later optimizations use it in a way as if it meant
"it must be alloca".  However I have not been able to come up with
a test case that makes this assumption false, but I probably just
did not try hard enough.

But I think that alloca just should not be recognized by name any
more.

And those optimizations probably aren't safe in the presence of allocaimplemented on top of malloc. They are safe for the built-in alloca though.


jeff

References:
- Re: [PATCH] Fix unsafe function attributes for special functions (PR 71876)
  - From: Bernd Edlinger

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