Re: [PATCH] add support for strnlen (PR 81384)

[Jeff Law <law@redhat.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