[cfe-dev] Missing NoReturnAttr in the AST?

[Hubert Tong via cfe-dev]

On Fri, Oct 4, 2019 at 6:12 AM Gábor Márton via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> I've found that the GCC __attribute__((noreturn)) is part of the type, and
> not parsed into a separate AST node like the C++11 [[noreturn]] or the GNU
> __attribute__((analyzer_noreturn)).
> To query the GCC __attribute__((noreturn)) we can use
> FunctionType::getNoReturnAttr().
>
> Why do we have these differences, with these attributes, why was the GCC
> noreturn uplifted into the Type?
>
Because it applies to function types:
typedef void (*fptype)(void) __attribute__((__noreturn__));
int f(int x, fptype fp) {
  if (x) return 42;
  fp();
}


>
> Thanks,
> Gabor
>
> On Fri, Oct 4, 2019 at 11:40 AM Gábor Márton <martongabesz at gmail.com>
> wrote:
>
>> Hi,
>>
>> Having a source file (/tmp/attr.cpp)
>>   void f() __attribute__((analyzer_noreturn));
>>   void g() __attribute__((noreturn));
>>   [[gnu::noreturn]] void h(void);
>> Generates the following AST, when clang -cc1 -ast-dump /tmp/attr.cpp is
>> used
>>   |-FunctionDecl 0x18a5178 </tmp/attr.cpp:1:1, col:43> col:6 f 'void ()'
>>   | `-AnalyzerNoReturnAttr 0x18a5218 <col:25>
>>   |-FunctionDecl 0x18a5308 <line:2:1, col:34> col:6 g 'void ()
>> __attribute__((noreturn))'
>>   `-FunctionDecl 0x18a5440 <line:3:19, col:30> col:24 h 'void ()
>> __attribute__((noreturn))'
>>
>> I.e. the NoReturnAttr node is missing. This is very confusing, when
>> compared to the AnalyzerNoReturnAttr, which is there.
>> The only difference in Attr.td is that noreturn has GCC spelling, while
>> analyzer_noreturn has GNU spelling.
>> What am I missing to have a NoReturnAttr node? Do I have to specify a
>> special extra flag for CC1 to enable GCC attributes?
>>
>> Thanks,
>> Gabor
>>
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