Re: [PATCH 1/3] improve detection of attribute conflicts (PR 81544)

[Jeff Law <law at redhat dot com>]

On 09/20/2017 12:04 PM, Martin Sebor wrote:
> On 09/19/2017 03:00 PM, Joseph Myers wrote:
>> On Tue, 19 Sep 2017, Martin Sebor wrote:
>>
>>>> In general, the data structures where you need to ensure manually that if
>>>>
>>>> attribute A is listed in EXCL for B, then attribute B is also listed in
>>>> EXCL for A, seem concerning.  I'd expect either data structures that make
>>>>
>>>> such asymmetry impossible, or a self-test that verifies that the tables in
>>>>
>>>> use are in fact symmetric (unless there is some reason the symmetry is not
>>>>
>>>> in fact required and symmetric diagnostics still result from asymmetric
>>>> tables - in which case the various combinations and orderings of
>>>> gnu_inline and noinline definitely need tests to show that the diagnostics
>>>>
>>>> work).
>>>
>>> If I understand correctly what you're concerned about then I don't
>>> think there are any such cases in the updated version of the patch.
>>
>> I don't see how you ensure that it's not possible to have such asymmetry.
>> My point wasn't so much "there was a bug in the previous patch version" as
>>
>> "the choice of data structures for defining such exclusions is prone to
>> such bugs".  Which can be addressed either by using different data
>> structures (e.g. listing incompatible pairs in a single array) or by a
>> self-test to verify symmetry so a compiler with asymmetry doesn't build.
> 
> Okay, that's a useful thing to add.  It exposed a couple of missing
> attribute exclusions that I had overlooked.  Thanks for the suggestion!
> Attached is an incremental diff with just these changes to make review
> easier and an updated patch.
> 
> As an aside, there are a number of other possible logic errors in
> the attribute specifications that could be detected by self-tests.
> The one I ran into is misspelled attribute names.  The added test
> detects misspelled names in exclusions, but not in the main specs.
> 
> Martin
> 
> gcc-81544-1-inc.diff
> 
> 


> gcc-81544-1.diff
> 
> 
> PR c/81544 - attribute noreturn and warn_unused_result on the same function accepted
> 
> gcc/c/ChangeLog:
> 
> 	PR c/81544
> 	* c-decl.c (c_decl_attributes): Look up existing declaration and
> 	pass it to decl_attributes.
> 
> gcc/c-family/ChangeLog:
> 
> 	PR c/81544
> 	* c-attribs.c (attr_aligned_exclusions): New array.
> 	(attr_alloc_exclusions, attr_cold_hot_exclusions): Same.
> 	(attr_common_exclusions, attr_const_pure_exclusions): Same.
> 	(attr_gnu_inline_exclusions, attr_inline_exclusions): Same.
> 	(attr_noreturn_exclusions, attr_returns_twice_exclusions): Same.
> 	(attr_warn_unused_result_exclusions): Same.
> 	(handle_hot_attribute, handle_cold_attribute): Simplify.
> 	(handle_const_attribute): Warn on function returning void.
> 	(handle_pure_attribute): Same.
> 	* c-warn.c (diagnose_mismatched_attributes): Simplify.
> 
> gcc/ChangeLog:
> 
> 	PR c/81544
> 	* attribs.c (empty_attribute_table): Initialize new member of
> 	struct attribute_spec.
> 	(decl_attributes): Add argument.  Handle mutually exclusive
> 	combinations of attributes.
> 	* attribs.h (decl_attributes): Add default argument.
> 	* selftest.h (attribute_c_tests): Declare.
> 	* selftest-run-tests.c (selftest::run_tests): Call attribute_c_tests.
> 	* tree-core.h (attribute_spec::exclusions, exclude): New type and
> 	member.
> 	* doc/extend.texi (Common Function Attributes): Update const and pure.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c/81544
> 	* c-c++-common/Wattributes-2.c: New test.
> 	* c-c++-common/Wattributes.c: New test.
> 	* c-c++-common/attributes-3.c: Adjust.
> 	* gcc.dg/attr-noinline.c: Adjust.
> 	* gcc.dg/pr44964.c: Same.
> 	* gcc.dg/torture/pr42363.c: Same.
> 	* gcc.dg/tree-ssa/ssa-ccp-2.c: Same.
OK.
jeff