Re: [Boost-users] [wave] Wave macro expansion problem

Subject: Re: [Boost-users] [wave] Wave macro expansion problem
From: Edward Diener (eldiener_at_[hidden])
Date: 2013-09-10 07:49:15

On 9/10/2013 7:13 AM, Hartmut Kaiser wrote:
>
>> The code:
>>
>> // test_macros_o.cpp
>>
>> #define f(a) f(x + (a))
>> #define x 2
>> #define g f
>> #define h g(~
>>
>> int main()
>>     {
>>
>> #pragma wave trace(enable)
>>
>>     h 5);
>>
>> #pragma wave trace(disable)
>>
>>     return 0;
>>     }
>>
>> In the latest C++ standard at 16.3.5 paragraph 5 the expansion of 'h 5)'
>> is given as:
>>
>> f(2 * (~5))
>>
>> but the wave.exe driver gives:
>>
>> C:\Programming\VersionControl\boost\libs\vmd\test\test_macros_o.cpp:11:3:
>> h
>>
>> C:\Programming\VersionControl\boost\libs\vmd\test\test_macros_o.cpp:4:9:
>> see macro definition: h
>>     [
>>       g(~
>>       rescanning
>>       [
>>
>> C:\Programming\VersionControl\boost\libs\vmd\test\test_macros_o.cpp:3:9:
>> see macro definition: g
>>         [
>>           f
>>           rescanning
>>           [
>>             f
>>           ]
>>         ]
>
> It actually should say something like:
>
> t.cpp:13:4: error: improperly terminated macro invocation or replacement-
> list terminates in partial macro expansion (not supported yet): missing ')'

You are correct. It does say this on stderr. Sorry for the noise.

>
> This is a known bug in wave caused by its recursive expansion algorithm
> which does not allow to handle this pathologic corner case. All I could do
> was to detect and report this.

It might be worth it to fix this known bug.