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Re: [PATCH] add support for strnlen (PR 81384)
- 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: Tue, 12 Jun 2018 15:11:02 -0600
- Subject: Re: [PATCH] add support for strnlen (PR 81384)
- References: <d72c0492-28aa-0d90-ee82-53520583bb73@gmail.com>
On 06/05/2018 03:43 PM, Martin Sebor wrote:
> The attached patch adds basic support for handling strnlen
> as a built-in function. It touches the strlen pass where
> it folds constant results of the function, and builtins.c
> to add simple support for expanding strnlen calls with known
> results. It also changes calls.c to detect excessive bounds
> to the function and unsafe calls with arguments declared
> attribute nonstring.
>
> A side-effect of the strlen change I should call out is that
> strlen() calls to all zero-length arrays that aren't considered
> flexible array members (i.e., internal members or non-members)
> are folded into zero. No warning is issued for such invalid
> uses of zero-length arrays but based on the responses to my
> question Re: aliasing between internal zero-length-arrays and
> other members(*) it sounds like one would be appropriate.
> I will see about adding one in a separate patch.
>
> Martin
>
> [*] https://gcc.gnu.org/ml/gcc/2018-06/msg00046.html
>
> gcc-81384.diff
>
>
> PR tree-optimization/81384 - built-in form of strnlen missing
>
> gcc/ChangeLog:
>
> PR tree-optimization/81384
> * builtin-types.def (BT_FN_SIZE_CONST_STRING_SIZE): New.
> * builtins.c (expand_builtin_strnlen): New function.
> (expand_builtin): Call it.
> (fold_builtin_n): Avoid setting TREE_NO_WARNING.
> * builtins.def (BUILT_IN_STRNLEN): New.
> * calls.c (maybe_warn_nonstring_arg): Handle BUILT_IN_STRNLEN.
> Warn for bounds in excess of maximum object size.
> * tree-ssa-strlen.c (maybe_set_strlen_range): Return tree representing
> single-value ranges. Handle strnlen.
> (handle_builtin_strlen): Handle strnlen.
> (strlen_check_and_optimize_stmt): Same.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/81384
> * gcc.c-torture/execute/builtins/lib/strnlen.c: New test.
> * gcc.c-torture/execute/builtins/strnlen-lib.c: New test.
> * gcc.c-torture/execute/builtins/strnlen.c: New test.
> * gcc.dg/attr-nonstring-2.c: New test.
> * gcc.dg/attr-nonstring-3.c: New test.
> * gcc.dg/attr-nonstring-4.c: New test.
> * gcc.dg/strlenopt-44.c: New test.
> * gcc.dg/strlenopt.h (strnlen): Declare.
>
> diff --git a/gcc/builtin-types.def b/gcc/builtin-types.def
> index 5365bef..1f15350 100644
> --- a/gcc/builtin-types.def
> +++ b/gcc/builtin-types.def
> @@ -322,6 +322,8 @@ DEF_FUNCTION_TYPE_2 (BT_FN_STRING_CONST_STRING_INT,
> BT_STRING, BT_CONST_STRING, BT_INT)
> DEF_FUNCTION_TYPE_2 (BT_FN_STRING_CONST_STRING_SIZE,
> BT_STRING, BT_CONST_STRING, BT_SIZE)
> +DEF_FUNCTION_TYPE_2 (BT_FN_SIZE_CONST_STRING_SIZE,
> + BT_SIZE, BT_CONST_STRING, BT_SIZE)
> DEF_FUNCTION_TYPE_2 (BT_FN_INT_CONST_STRING_FILEPTR,
> BT_INT, BT_CONST_STRING, BT_FILEPTR)
> DEF_FUNCTION_TYPE_2 (BT_FN_INT_INT_FILEPTR,
I believe Jakub already suggested these change and you ack'd that.
You have some hunks which will need updating now that the CHKP/MPX bits
are gone.
So OK after the cleanups noted above and a fresh bootstrap & regression
test cycle.
jeff