[PATCH] add support for strnlen (PR 81384)

[Martin Sebor]

On 06/12/2018 03:11 PM, Jeff Law wrote:
> 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.
>

Done.  I also added documentation for the built-in, reran GCC
and Glibc tests with no regressions, and committed 261705.

Martin