Re: /lib/cpp not found in c-mode

[Jan D.]

> > The information you see in gdb is all from the debug info in the
> > executable, so it does not require knowledge of include paths and
> > predefined macros.  The compilation of the executable does, but after
> > that it is all in the debug info, so gdb does not care what the
> > include paths where at the time of compilation.
> >
> >      Jan D.
>
> Sorry, yes you're right it doesn't care what the include paths  
> where. But my
> point is that it can expand all the macros while "gcc -E" can't.  
> "gcc -E" is
> typically given the source file as input but if it was also given the
> executable, it presumably could be adapted so that it could expand  
> all the
> macros just like GDB can.
>
> Would that not be a worthwhile thing to do?

If the executable exists already, why am I typing in the source code  
in Emacs? :-)
gcc -E can expand the macros just fine, it just needs the same input  
(-I -D and -U) as gcc got when creating the executable.  As others  
pointed out, it is impractical to set this up if you are working on  
several different projects at once.

Personally I don't see the need for expanding macros.  One of the  
reasons I use them in the first place is to hide details I don't need  
to see.  Expanding them while editing seems a strange thing to do.

    Jan D.