Hello experts,

I need to conditionate the compilation of functions in a C file by
macro definitions. I'll give an example of what I've been trying to
get, but I also accept any answer or suggestion that leads to the same
result, provided it works with the standard GNU compilation tools.

I have a set of C functions in a file, and I want to be able to
enable/disable their compilation by setting or not a macro. Here is a
short example:

#ifdef compile_A
void A()
{
  ...
}
#endif

#ifdef compile_B
void B()
{
  ..
}
#endif

However, in my case I'm manipulating very long function names. I'd
like to obtain the same effet by a set of preprocessor macros such as:

DEFINE_FUNCTION(A)
 ..
END_FUNCTION

DEFINE_FUNCTION(B)
 ..
END_FUNCTION

These macros would expand to the same output as above, or something
completely equivalent.

After digging through the cpp documentation, I have been unable to
find something that would do. I don't want to use any other layer of
preprocessing, so if someone would have a solution that works with the
standard GNU cpp, that'd be just great.

---

Request for Question Clarification by maniac-ga on 25 May 2005 16:38 PDT

Hello Gnurou,

Would you be willing to run the C preprocessor as an added step prior
to the C compiler?

The general solution to what you ask (nested evaluation of
preprocessor directives) is not possible in C (it was in Jovial, but
alas not C). [and I would explain why in a complete answer]

It would also be possible to automate that extra step using a
Makefile; I would explain that as well.

  --Maniac

---

Clarification of Question by gnurou-ga on 25 May 2005 23:07 PDT

It should be acceptable to run the preprocessor separately, although
I'd prefer not to generate intermediate files. But if there is no
other solution, I'll accept that too. Anyway, I'm already using a
Makefile. Please go ahead. :)

It is common to run an ealier layer of pre-processing on s/w with autoconf.
Recall the many INSTALL files containing these steps where the
configure command sets the appropriate macro definitions in the
Makefile.

./configure
make
make test
make install