Re: gnome-vfs circular build dependency

[James Henstridge <james daa com au>]

On 19/02/04 12:04, Dmitry G. Mastrukov wrote:

> I was just about too. More of that I was naot able to build gnome-vfs
> unless I changed check in configure.in from
> PKG_CHECK_MODULES(GTK, gtk+-2.0 >= 2.3.1 libgnomeui-2.0 >= 2.5.1, AM_CONDITIONAL(HAVE_GTK, true))
> to 
> PKG_CHECK_MODULES(GTK, gtk+-2.0 >= 2.3.1 libgnomeui-2.0 >= 2.5.1, AM_CONDITIONAL(HAVE_GTK, true), AM_CONDITIONAL(HAVE_GTK, false))
>
> IMHO cross-dependency is a bad idea. I think functionality from gtk
> subdir in gnome-vfs should be merged in libgnomeui or a new module for
> it should be created.
>  
Note that this actually highlights a common configure.in bug.  It is an 
error to put an AM_CONDITIONAL() statement inside a branch like that.

The way AM_CONDITIONAL works is by evaluating the condition, then 
defining the substitutions COND_TRUE and COND_FALSE to "" and "#", 
depending on the value.  The Makefile.in then contains lines like:
   @COND_TRUE@ do this if condition is true
   @COND_FALSE@ do this if condition is false

So in the resulting Makefile, one branch will be active and the other 
commented out.

Unfortunately, if the AM_CONDITIONAL doesn't get executed (because it is 
masked by an if statement), both the substitutions will be "", so both 
branches in the Makefile will be active and things break.

For automake >= 1.6 (or maybe 1.5), the AM_CONDITIONAL implementation 
adds some code to detect this case, causing configure to error out if 
the AM_CONDITIONAL doesn't get executed.

James.

--
Email: james daa com au
WWW:   http://www.daa.com.au/~james/