Re: Autoconf's main purpose is config.h generation that *just* has #define's right?...

[Ronald Landheer-Cieslak]

The *result* of the autoconf-generated configure script is "just a bunch 
of defines".

The configure.{ac|in} file is used to generate a shell-script that will be 
used to scan the system for its abilities - at least, the ones you ask to 
have checked. (That's where the "arbitrary shell code" is run). You could 
effectively put shell code in the configure.{ac|in} file and thus have it 
run at configure time.

Anyways, the configure script uses a Makefile.in file (which might also 
contain shell code to be run at compile-time) to generate a Makefile, and 
may generate a config.h file if you ask it to do so. It will also make 
sure that the results of what it found are available in the form of 
defines at compile-time, so you can do the 
        #if HAVE_PRINTF
        printf("Hello, world!\n");
        #endif
thing.

HTH

rlc

On Wed, 16 Apr 2003 address@hidden wrote:

> I've spent a lot of time reading Autotools docs
> and just wanted to verify something before I get
> lost in the info overload.....
> 
> In general,
> the way to write portable and _flexible_ C code is to have
> preprocessor directives like:
> 
> #ifdef STDIO_H_IS_AVAILABLE
>    printf("Hello world.n");
> #endif
> 
> .... and the way those variables
> get defined is to include config.h which is built by configure
> script which is built by Autoconf right?
> 
> In a nutshell, one should not be intimidated by Autoconf
> because it does not do anything more profound or deep
> than just make a bunch of #define's right???
> 
> ...
> 
> (The reason this was not obvious is because I read that
> one can run arbitrary shell code with Autoconf/configure
> system.  This implies Autoconf can do more than I thought
> and so I got confused.)
> 
> **What else would you use
> Autoconf for other than making a list of #defines*?
> 
> Thanks,
> 
> Chris
> 
> 
> 
>