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Re: [PATCH] restore -Wstringop-overflow for checked strcpy/strcat (PR 85259)
- From: Jeff Law <law at redhat dot com>
- To: Martin Sebor <msebor at gmail dot com>, Gcc Patch List <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 11 Jun 2018 15:25:41 -0600
- Subject: Re: [PATCH] restore -Wstringop-overflow for checked strcpy/strcat (PR 85259)
- References: <9a8db8a9-acd7-665a-1300-a295e1945bf3@gmail.com>
On 05/14/2018 04:41 PM, Martin Sebor wrote:
> r256683 committed to GCC 8 to avoiding duplicate instances of
> -Wstringop-overflow warnings on some targets has the unintended
> side-effect of suppressing even singleton instances of the warning
> in cases such as 'strcat (strcpy (buf, "hello "), "world!")' when
> _FORTIFY_SOURCE is defined.
>
> The attached patch restores the warning for the trunk.
>
> Since this is a regression in a security feature and the warning
> isn't prone to false positives (I don't think I've seen any when
> _FORTIFY_SOURCE is defined), I'd also like the fix considered for
> the 8 branch.
>
> Thanks
> Martin
>
> gcc-85259.diff
>
>
> PR tree-optimization/85259 - Missing -Wstringop-overflow= since r256683
>
> gcc/ChangeLog:
>
> PR tree-optimization/85259
> * builtins.c (compute_objsize): Handle constant offsets.
> * gimple-ssa-warn-restrict.c (maybe_diag_offset_bounds): Return
> true iff a warning has been issued.
> * gimple.h (gimple_nonartificial_location): New function.
> * tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Call
> gimple_nonartificial_location and handle -Wno-system-headers.
> (handle_builtin_stxncpy): Same.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/85259
> * gcc.dg/Wstringop-overflow-5.c: New test.
> * gcc.dg/Wstringop-overflow-6.c: New test.
OK for the trunk.
The general guidance we've received is to not try and fix these on the
release branches. However, I think this one deserves an exception to
the general guidance. So OK for the gcc-8 branch.
jeff