r173952 - [preprocessor] Don't warn about "disabled expansion of recursive macro"

[Richard Smith]

On Wed, Jan 30, 2013 at 12:44 PM, Argyrios Kyrtzidis <akyrtzi at gmail.com> wrote:
> On Jan 30, 2013, at 11:54 AM, Abramo Bagnara <abramo.bagnara at gmail.com> wrote:
>
>> Il 30/01/2013 19:55, Argyrios Kyrtzidis ha scritto:
>>> Author: akirtzidis
>>> Date: Wed Jan 30 12:55:52 2013
>>> New Revision: 173952
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=173952&view=rev
>>> Log:
>>> [preprocessor] Don't warn about "disabled expansion of recursive macro"
>>> for "#define X X".
>>>
>>> This is a pattern that, for example, stdbool.h uses.
>>> rdar://12435773
>>
>> Please revert this commit: this has already been discussed in detail in
>> past and we decided otherwise. Last time it has been discussed in this
>> thread:
>>
>> http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20121029/067098.html
>
> Reverted in r173970.
>
>>
>>>
>>> Modified:
>>>    cfe/trunk/lib/Lex/PPMacroExpansion.cpp
>>>    cfe/trunk/test/Headers/stdbool.cpp
>>>    cfe/trunk/test/Preprocessor/warn-disabled-macro-expansion.c
>>>
>>> Modified: cfe/trunk/lib/Lex/PPMacroExpansion.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Lex/PPMacroExpansion.cpp?rev=173952&r1=173951&r2=173952&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/lib/Lex/PPMacroExpansion.cpp (original)
>>> +++ cfe/trunk/lib/Lex/PPMacroExpansion.cpp Wed Jan 30 12:55:52 2013
>>> @@ -459,7 +459,10 @@ bool Preprocessor::HandleMacroExpandedId
>>>       if (MacroInfo *NewMI = getMacroInfo(NewII))
>>>         if (!NewMI->isEnabled() || NewMI == MI) {
>>>           Identifier.setFlag(Token::DisableExpand);
>>> -          Diag(Identifier, diag::pp_disabled_macro_expansion);
>>> +          // Don't warn for "#define X X" like "#define bool bool" from
>>> +          // stdbool.h.
>>
>> Would you be so kind to add a comment here to remember that the choice
>> to have this warning for thar case (although disabled by default) is
>> deliberate?
>
> Just to make sure, are you of the opinion that we should warn when <stdbool.h> is included and its macros are used ?

As discussed on that thread, we should modify <stdbool.h> to suppress
the warning.