r291963 - [clang] Emit `diagnose_if` warnings from system headers

[Hans Wennborg via cfe-commits]

Richard, what do you think?

On Fri, Jan 13, 2017 at 3:16 PM, Eric Fiselier <eric at efcs.ca> wrote:
> I would love to see this merged. It would make it easier to write libc++
> tests if the tests didn't have to worry about the old 4.0 behavior.
>
> CC'ing Richard: Would merging this be OK?
>
> On Fri, Jan 13, 2017 at 3:46 PM, George Burgess IV
> <george.burgess.iv at gmail.com> wrote:
>>
>> Do we want to consider merging this into the release branch? Seems like
>> more of a bugfix than a feature to me.
>>
>> On Fri, Jan 13, 2017 at 2:11 PM, Eric Fiselier via cfe-commits
>> <cfe-commits at lists.llvm.org> wrote:
>>>
>>> Author: ericwf
>>> Date: Fri Jan 13 16:11:40 2017
>>> New Revision: 291963
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=291963&view=rev
>>> Log:
>>> [clang] Emit `diagnose_if` warnings from system headers
>>>
>>> Summary: In order for libc++ to meaningfully use `diagnose_if` warnings
>>> they need to be emitted from system headers by default. This patch changes
>>> the `diagnose_if` warning diagnostic to be shown in system headers.
>>>
>>> Reviewers: george.burgess.iv, rsmith, aaron.ballman
>>>
>>> Subscribers: cfe-commits
>>>
>>> Differential Revision: https://reviews.llvm.org/D28703
>>>
>>> Added:
>>>     cfe/trunk/test/Sema/Inputs/diagnose-if-warn-system-header.h
>>> Modified:
>>>     cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>     cfe/trunk/test/Sema/diagnose_if.c
>>>
>>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=291963&r1=291962&r2=291963&view=diff
>>>
>>> ==============================================================================
>>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Jan 13
>>> 16:11:40 2017
>>> @@ -3380,7 +3380,8 @@ def note_ovl_candidate_has_pass_object_s
>>>      "candidate address cannot be taken because parameter %0 has "
>>>      "pass_object_size attribute">;
>>>  def err_diagnose_if_succeeded : Error<"%0">;
>>> -def warn_diagnose_if_succeeded : Warning<"%0">,
>>> InGroup<UserDefinedWarnings>;
>>> +def warn_diagnose_if_succeeded : Warning<"%0">,
>>> InGroup<UserDefinedWarnings>,
>>> +    ShowInSystemHeader;
>>>  def note_ovl_candidate_disabled_by_function_cond_attr : Note<
>>>      "candidate disabled: %0">;
>>>  def note_ovl_candidate_disabled_by_extension : Note<
>>>
>>> Added: cfe/trunk/test/Sema/Inputs/diagnose-if-warn-system-header.h
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/Inputs/diagnose-if-warn-system-header.h?rev=291963&view=auto
>>>
>>> ==============================================================================
>>> --- cfe/trunk/test/Sema/Inputs/diagnose-if-warn-system-header.h (added)
>>> +++ cfe/trunk/test/Sema/Inputs/diagnose-if-warn-system-header.h Fri Jan
>>> 13 16:11:40 2017
>>> @@ -0,0 +1,11 @@
>>> +#pragma GCC system_header
>>> +
>>> +inline int system_header_func(int x)
>>> +  __attribute__((diagnose_if(x == x, "system header warning",
>>> "warning"))) // expected-note {{from 'diagnose_if' attribute}}
>>> +{
>>> +  return 0;
>>> +}
>>> +
>>> +void test_system_header() {
>>> +  system_header_func(0); // expected-warning {{system header warning}}
>>> +}
>>>
>>> Modified: cfe/trunk/test/Sema/diagnose_if.c
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/diagnose_if.c?rev=291963&r1=291962&r2=291963&view=diff
>>>
>>> ==============================================================================
>>> --- cfe/trunk/test/Sema/diagnose_if.c (original)
>>> +++ cfe/trunk/test/Sema/diagnose_if.c Fri Jan 13 16:11:40 2017
>>> @@ -150,3 +150,6 @@ void alwaysWarnWithArg(int a) _diagnose_
>>>  void runAlwaysWarnWithArg(int a) {
>>>    alwaysWarnWithArg(a); // expected-warning{{alwaysWarn}}
>>>  }
>>> +
>>> +// Test that diagnose_if warnings generated in system headers are not
>>> ignored.
>>> +#include "Inputs/diagnose-if-warn-system-header.h"
>>>
>>>
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>>> cfe-commits at lists.llvm.org
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>>
>>
>