Re: [PATCH] stdnoreturn: new module

[Bruno Haible]

Hi Paul,
> > The current set of definitions
> > 
> >   #define _Noreturn __declspec (noreturn)
> >   #define noreturn _Noreturn
> > 
> > leads to a syntax error when someone writes  __declspec (noreturn),
> > because preprocessing transforms it to  __declspec (__declspec (noreturn)).
> > 
> > How can this syntax error be avoided?
> 
> I don't see any reasonable way to do it.

If we could redefine __declspec, it would be possible. Like this:

$ cat foo.c

  #define noreturn __declspec(noreturn)
  #define _Noreturn noreturn

  #define __declspec(a) __declspec1(a)
  #define __declspec1(a) __wrapped_##a
  #define __wrapped_noreturn __declspec(noreturn1)
  #define __wrapped_noreturn1 __declspec(noreturn)
  #define __wrapped___wrapped_noreturn __declspec1(noreturn2)
  #define __wrapped_noreturn2 noreturn

  __declspec(noreturn) void exit (int);
  noreturn void exit (int);

$ cl -E foo.c
...
  __declspec(noreturn) void exit (int);
  __declspec(noreturn) void exit (int);

But unfortunately there are also other possible elements in a declspec
list, see [1]. I don't see how to accommodate these.

And interestingly, this preprocessor output from 'cl' is different
from the one that gcc produces. With gcc, it's easier:

$ cat foo.c

  #define noreturn __declspec(noreturn)
  #define _Noreturn noreturn

  #define __declspec(a) __wrapped_##a
  #define __wrapped_noreturn __attribute__((__noreturn__))

  __declspec(noreturn) void exit (int);
  noreturn void exit (int);

$ gcc -E foo.c
...
  __attribute__((__noreturn__)) void exit (int);
  __attribute__((__noreturn__)) void exit (int);


Bruno

[1] http://msdn.microsoft.com/en-us/library/dabb5z75%28v=vs.80%29.aspx