Re: CC Mode and GCC/CEDET integration for evaluating macros

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 02 May 2015 11:27:22 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: acm@muc.de, emacs-devel@gnu.org
> 
> > c-macro-expansion: Search failed: "
> > ??? !!! ??? start of c-macro expansion ??? !!! ???"
> 
> This generally means that cpp exited with some error, I think.  (yes,
> the error message could be improved.)  I suggest to step with a
> debugger through the relevant functions in cmacexp.el, it's possible
> there's a bug there.

In fact, there was indeed a bug in the code that handled abnormal exit
status of the preprocessor: it would bail out early without showing
the error messages emitted by the preprocessor, which are an important
clue as to what went wrong.  For example, if you don't pass any
options to the preprocessor, it fails with this error message:

  <stdin>:21:20: fatal error: config.h: No such file or directory
  compilation terminated.

which clearly suggests that you need to pass at least the -I. switch.

I fixed this.