bug#38511: etags seems to be confused by macros

[Eli Zaretskii <eliz@gnu.org>]

> From: Skip Montanaro <skip.montanaro@gmail.com>
> Date: Fri, 6 Dec 2019 14:20:14 -0600
> 
> I use speedbar in Emacs, which relies on etags to generate tag files.
> The Python source defines a macro named Py_LOCAL_INLINE, which is used
> to select the appropriate spelling of "static inline":
> 
> #if defined(_MSC_VER)
> ...
> #  define Py_LOCAL_INLINE(type) static __inline type __fastcall
> #else
> ...
> #  define Py_LOCAL_INLINE(type) static inline type
> #endif
> 
> It's used like so:
> 
> Py_LOCAL_INLINE(void)
> stackdepth_push(basicblock ***sp, basicblock *b, int depth)
> {
>     assert(b->b_startdepth < 0 || b->b_startdepth == depth);
>     if (b->b_startdepth < depth && b->b_startdepth < 100) {
>         assert(b->b_startdepth < 0);
>         b->b_startdepth = depth;
>         *(*sp)++ = b;
>     }
> }
> 
> It all works well. Etags though, thinks the file contains a function
> named "Py_LOCAL_INLINE" and completely misses the actual function,
> "stackdepth_push".

Etags works by looking at the source at face value, and it doesn't
expand macros as a C compiler would.  So this:

  Py_LOCAL_INLINE(void) stackdepth_push(basicblock ***sp, basicblock *b, int depth)

looks to its naïve lexical analysis very much like a K&R definition of
a function and declaration of its arguments:

  Py_LOCAL_INLINE(foo) int foo(bar)

> Seems like a bug to me, but it's not obvious if there is a trivial
> fix.

Patches are welcome, if someone has an idea for how to fix that.

Thanks.