Re: [PATCH] Fix PR 86572

[Jeff Law <law at redhat dot com>]

On 11/5/18 4:20 PM, Bernd Edlinger wrote:
> On 11/5/18 1:28 AM, H.J. Lu wrote:
>> On Sun, Nov 4, 2018 at 10:02 AM Jeff Law <law@redhat.com> wrote:
>>> On 10/22/18 9:08 AM, Bernd Edlinger wrote:
>>>> Hi!
>>>>
>>>> This makes c_strlen avoid an unsafe strlen folding of const arguments
>>>> with non-const offset.  Currently a negative out of bounds offset
>>>> makes the strlen function return an extremely large number, and
>>>> at the same time, prevents the VRP machinery, to determine the correct
>>>> range if the strlen function in this case.
>>>>
>>>> Fixed by doing the whole computation in size_t and casting the
>>>> result back to ssize_t.
>>>>
>>>>
>>>> Bootstrapped and reg-tested on x86_64-pc-linux-gnu.
>>>> Is it OK for trunk?
>>>>
>>>>
>>>> Thanks
>>>> Bernd.
>>>>
>>>>
>>>> patch-pr86572.diff
>>>>
>>>> gcc:
>>>> 2018-10-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>
>>>>
>>>>        PR tree-optimization/86572
>>>>        * builtins.c (c_strlen): Handle negative offsets in a safe way.
>>>>
>>>> testsuite:
>>>> 2018-10-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>
>>>>
>>>>        PR tree-optimization/86572
>>>>        * gcc.dg/pr86572.c: New test.
>>> OK.
>>> jeff
>> This caused:
>>
>> /export/gnu/import/git/gcc-test-ia32/src-trunk/gcc/testsuite/gcc.dg/warn-strlen-no-nul.c:56:1:
>> internal compiler error: verify_gimple failed^M
>> 0x8922dc4 verify_gimple_in_seq(gimple*)^M
>>          ../../src-trunk/gcc/tree-cfg.c:5082^M
>> 0x86899d7 gimplify_body(tree_node*, bool)^M
>>          ../../src-trunk/gcc/gimplify.c:12859^M
>> 0x8689b8b gimplify_function_tree(tree_node*)^M
>>          ../../src-trunk/gcc/gimplify.c:12949^M
>> 0x84f7690 cgraph_node::analyze()^M
>>          ../../src-trunk/gcc/cgraphunit.c:667^M
>> 0x84fa1d8 analyze_functions^M
>>          ../../src-trunk/gcc/cgraphunit.c:1126^M
>> 0x84fadd3 symbol_table::finalize_compilation_unit()^M
>>          ../../src-trunk/gcc/cgraphunit.c:2833^M
>> Please submit a full bug report,^M
>> with preprocessed source if appropriate.^M
>> Please include the complete backtrace with any bug report.^M
>> See <https://gcc.gnu.org/bugs/> for instructions.^M
>> compiler exited with status 1
>> FAIL: gcc.dg/warn-strlen-no-nul.c (internal compiler error)
>>
>> on i386.
>>
> Ah yes thanks.
> 
> This is caused by an incorrect folding in string_constant.
> After stripping the type casts in the POINTER_PLUS_EXPR
> we add the offset which is sizetype to what is left
> over from arg1, which is probably even a correctness issue,
> if the type cast was a narrowing one.
> 
> Bootstrapped and reg-tested on x86_64-pc-linux-gnu (this time
> tested with RUNTESTFLAGS="--target_board=unix\{-m32,\}")
> Is it OK for trunk?
> 
> 
> Thanks
> Bernd.
> 
> 
> 
> patch-fix-string-cst.diff
> 
> 2018-11-05  Bernd Edlinger  <bernd.edlinger@hotmail.de>
> 
> 	* expr.c (string_constant): Don't strip NOPS in subexpressions.
> 	Fold PLUS_EXPR correctly.
OK.
jeff