Re: Build warning in Glib

[Jon Trowbridge <trow ximian com>]

On 17 Jun 2001 11:11:30 +0530, Ravi Pratap M wrote:
> 	Having just got all the GNOME 2 modules, I began compiling them
> and while in glib, I got a huge number of these messages :
> 
> configure.in:458: warning: AC_TRY_RUN called without default to allow
> cross compiling
> (and so on ...)
> 
> 	It does however go on to successfully generate the makefiles etc.


Here is the pedantic explanation of what is going on:

AC_TRY_RUN is an autoconf macro that attempts to compile, link and run a
program on your machine.  This sort of thing is used to check if you
have various libs, if they implement various functions properly, etc.

(This is also why running ./configure can be unexpectedly slow ---
behind the scenes, gcc is getting run a whole bunch of times.)

Besides the program to build, you are supposed to provide three pieces
of information for AC_TRY_TUN:
(1) What to do if the compile/link/run succeeds.
(2) What to do if the compile/link/run fails.
(3) What to do if you are cross-compiling, and thus can't even run the
test all.  This is supposed to be some sort of default or reasonable
fallback.

The information for (3) is frequently omitted, because most people don't
really care if cross-compiling is supported properly.  And this isn't a
problem for anyone who isn't cross-compiling, though it does produce a
lot of annoying warnings.

So you don't need to worry about it... but it would be nice if people
writing configure tests did. :)

-JT