Re: [Swig-devel] Problem expanding macro arguments within comments

[Robert L. t. G. <rh...@as...>]

I pointed out that swig doesn't strip comments in macros, which can lead
to surprising bugs.  William points out that using C83 /* comments */
avoids the problem, but I still think that this is unhelpful behaviour;
what would we lose by stripping comments?  Users assume that swig
understands // comments, so it's surprising that it doesn't in this  
case.

					R


> To me it is doing the right thing. %GOO(float) expands to (where \n  
> is a newline):
> \nfloat x;\n
>
> So %FOO(%GOO(float)) is then:
> \n// \nfloat x;\n ABC\n
>
> If you run swig -E, you'll see the resulting output, eg using this:
> /*start*/%FOO(%GOO(float));/*end*/
>
> you'll get:
>
> /*start*//*@SWIG:example.i,10,%FOO@*/
> // /*@SWIG:example.i,6,%GOO@*/
> float x;
> /*@SWIG@*/ ABC
> /*@SWIG@*/;/*end*/
>
> Consider using C comments rather than C++ comments as that will give  
> you what you want.


This will clearly work;  it's what you have to do in CPP macros too.

> Robert Lupton the Good wrote:
>> The following .i file generates a syntax error;  remove the comment  
>> in  %FOO
>> and all is well.  It's something about expanding an argument within a
>> comment, and I'd guess that the result of expanding %GOO includes  
>> the  newline
>> (which is usually what you want) --- so the ABC appears on a line  
>> of  its own.
>> If I'm right, we should strip comments before expanding macro  
>> arguments.
>> 				R
>> %module foo;
>> %define %GOO(ARG1)
>> ARG1 x;
>> %enddef
>> %define %FOO(ARG2)
>> // ARG2 ABC
>> %enddef
>> %FOO(%GOO(float));
>