Re: why not #include "config.h"?

[Thomas Dickey]

On Tue, 22 Sep 2009, Patrick Welche wrote:

> On Tue, Sep 22, 2009 at 10:49:58AM +0200, Steffen Dettmer wrote:
> > I hope I don't ask a FAQ. If so, an URL would be appreciated.
> >
> > I've read here that someone could (should?) write
> >   #include <config.h>
> > specifying a system header instead of the IMHO correct
> >   #include "config.h"
...
> 4.9 Configuration Header Files
> ==============================
> ....
>   To provide for VPATH builds, remember to pass the C compiler a `-I.'
> option (or `-I..'; whichever directory contains `config.h').  Even if
> you use `#include "config.h"', the preprocessor searches only the
> directory of the currently read file, i.e., the source directory, not
> the build directory.
>
>   With the appropriate `-I' option, you can use `#include <config.h>'.
> Actually, it's a good habit to use it, because in the rare case when
> the source directory contains another `config.h', the build directory
> should be searched first.

It doesn't mention the fact that the choice of starting directory for a 
nested include using quotes depends upon the compiler (the C standard 
leaves this as implementation-defined).  Given the source, it's 
understandable that it only provides a comment specific to gcc - however, 
that's the actual reason for preferring bracketed includes.

--
Thomas E. Dickey
http://invisible-island.net
ftp://invisible-island.net