From: Marc Glisse <marc.glisse@inria.fr>
To: Jeff Law <law@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: Warn when returning the address of a temporary (middle-end) v2
Date: Tue, 22 Jul 2014 09:04:00 -0000 [thread overview]
Message-ID: <alpine.DEB.2.11.1407221056190.1843@laptop-mg.saclay.inria.fr> (raw)
In-Reply-To: <53C746CC.1000007@redhat.com>
On Wed, 16 Jul 2014, Jeff Law wrote:
> On 06/22/14 12:20, Marc Glisse wrote:
>> Hello,
>>
>> I followed the advice in this discussion:
>> https://gcc.gnu.org/ml/gcc-patches/2014-04/msg00269.html
>>
>> and here is a new patch. I made an effort to isolate a path in at least
>> one subcase so it doesn't look too strange that the warning is in this
>> file. Computing the dominance info just to tweak the warning message may
>> be a bit excessive. I kept the same option as the front-ends, I don't
>> know if we want a different one, or maybe a Wmaybe-... version. There
>> will be cases where we get a duplicate warning from -Wtarget-lifetime in
>> fortran, but none in the testsuite, and I would rather have 2 warnings
>> than miss such broken code. The uninit-G testcase is about
>> initialization, not returning, so I am changing that, even if it is
>> unnecessary with the current version of the patch (only activated at -O2).
>>
>> Bootstrap+testsuite (--enable-languages=all,obj-c++,ada,go) on
>> x86_64-unknown-linux-gnu.
>>
>> (by the way, contrib/compare_tests is confused when I use all languages,
>> it prints "comm: file 1 is not in sorted order" and tons of spurious
>> differences)
>>
>> 2014-06-23 Marc Glisse <marc.glisse@inria.fr>
>>
>> PR c++/60517
>> gcc/c/
>> * c-typeck.c (c_finish_return): Return 0 instead of the address of
>> a local variable.
>> gcc/cp/
>> * typeck.c (maybe_warn_about_returning_address_of_local): Return
>> whether it is returning the address of a local variable.
>> (check_return_expr): Return 0 instead of the address of a local
>> variable.
>> gcc/c-family/
>> * c.opt (-Wreturn-local-addr): Move to common.opt.
>> gcc/
>> * common.opt (-Wreturn-local-addr): Moved from c.opt.
>> * gimple-ssa-isolate-paths.c: Include diagnostic-core.h.
>> (isolate_path): New argument to avoid inserting a trap.
>> (find_implicit_erroneous_behaviour): Handle returning the address
>> of a local variable.
>> (find_explicit_erroneous_behaviour): Likewise.
>> (gimple_ssa_isolate_erroneous_paths): Calculate dominance info.
>> gcc/testsuite/
>> * c-c++-common/addrtmp.c: New file.
>> * c-c++-common/uninit-G.c: Adapt.
> I note you don't catch return &localvar in the isolation code -- it looks
> like you just catch those which potentially flow from PHIs.
I thought I was handling it in the find_explicit_erroneous_behaviour part
of the patch (as opposed to the implicit part which deals with PHIs).
Function f1 in the testcase addrtmp.c has no PHI. Am I missing something?
> I realize you're primarily catching that in the front-ends, but can't we have
> cases which aren't caught by the front end, but after optimizations we're
> able to propagate &somelocal into the return statement?
We can, and it was my original motivation. I only added PHI handling when
you asked for it.
> It generally looks good and I'm ready to approve if the answer to the above
> question is "can't happen". If it can happen, then we ought to handle it in
> the isolation code as well (ought to be relatively easy).
Just to be clear, the approval would include the PARM_DECL tweak in
https://gcc.gnu.org/ml/gcc-patches/2014-06/msg02327.html
?
Thanks,
--
Marc Glisse
next prev parent reply other threads:[~2014-07-22 9:03 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-22 18:20 Marc Glisse
2014-06-29 9:22 ` Marc Glisse
2014-06-30 21:04 ` Jeff Law
2014-06-30 21:37 ` Marc Glisse
2014-07-02 12:19 ` Alan Modra
2014-07-02 12:41 ` Marc Glisse
2014-07-02 22:39 ` Jeff Law
2014-07-02 22:46 ` Jeff Law
2014-07-18 5:06 ` Jeff Law
2014-07-22 9:04 ` Marc Glisse [this message]
2014-07-31 4:54 ` Jeff Law
2014-07-27 18:20 ` Richard Sandiford
2014-07-27 19:09 ` Marc Glisse
2014-07-27 20:45 ` Andreas Schwab
2014-07-27 21:05 ` Marc Glisse
2014-07-29 19:00 ` Marc Glisse
2014-07-29 19:13 ` David Malcolm
2014-07-29 19:22 ` Marek Polacek
2014-07-29 19:47 ` David Malcolm
2014-07-29 19:28 ` Marc Glisse
2014-07-30 12:00 ` Marc Glisse
2014-07-31 4:58 ` Jeff Law
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