[PATCH] Fix PR 86572

[H.J. Lu]

On Mon, Nov 5, 2018 at 3:20 PM Bernd Edlinger <bernd.edlinger@hotmail.de> 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?
>

I opened:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87940

to track it.

-- 
H.J.