Re: GTK build crashes under X

[Jan Djärv]

Eli Zaretskii skrev:

> Btw, this pkg-config thingy is a terrible nuisance.  I recently had to
> build some package on a RH box, and was amazed to find that all the
> ``usual'' tricks of getting `configure' to use non-default include and
> library paths simply don't work, because that package's `configure'
> script used pkg-config to find all the headers and libraries, and as
> you say above, what pkg-config returns cannot be overridden easily.
> For example, "LDFLAGS=-L/whatever ./configure" cannot override the
> places where the linker run by `configure' looks for libraries.  This
> means, for example, that if you are an underprivileged user who
> installs packages and libraries under ~/, you have no hope of getting
> the compiler and the linker to use headers and libraries in those
> private directories, since pkg-config doesn't know about them and
> keeps pointing the build process to the public directories.

It can be a pain sometimes, but for the most part it works quite well.

> (If there's a reasonable way of working around this, please let me
> know.)

As Henrik Enberg pointed out:
"PKG_CONFIG_PATH=/path/to/dir/with/foo.pc ./configure"

PKG_CONFIG_PATH can be set like PATH, and pkg-config will search those 
directories for foo.pc.  This file defines what foo needs to compile and link, 
like for example gtk+-2.0.pc:

Requires: gdk-${target}-2.0 atk cairo

${target} expands to x11 in my case.

Then pkg-config searches for gdk-x11-2.0.pc, atk.pc and pango.pc, using the 
same PKG_CONFIG_PATH.

Do we document the LDFLAGS-trick somewhere?  We should add something about 
PKG_CONFIG_PATH there.

> I hope Emacs will _never_ use pkg-config for anything serious, because
> otherwise I will be at the mercy of the sysadmins on too many systems
> I work on, where I cannot become a superuser and "make install" the
> optional image libraries needed by Emacs.  (Also, most of the Emacs
> INSTALL file will become incorrect if we ever start using pkg-config,
> and even now the GTK build is already hit by this problem.)
>
> Why in the world would GNU/Linux developers wish to use such a
> restrictive tool?  Do they somehow miss the non-freedom of MS-Windows?

:-)  AFAIK pkg-config is available for MS-Windows.

The initial motivation (I think) was that the thing pkg-config does was too 
complicated for configure.  For example, if lib A needs lib X and Y, and lib B 
also needs X, you would before pkg-config have two -l/path/to/X -lX in your 
link command line.  And this would multiply.  I've seen command lines with the 
same stuff repeated over and over again so eventually the line was too long to 
execute.

It also manages cascading dependencies, i.e. A depends on X but X itself 
depends on B and maybe C if X version is > 1.4.  Then C depends on D and E.

This is too complicated for configure, so here pkg-config does a really nice 
job.

It is also very nice to be able to write in your Makefile:

PKG = libgnomeui-2.0
prog: $(OBJ)
        $(CXX) -o $@  $(OBJS) `pkg-config $(PKG) --libs`

and you get all required stuff linked in.

Also, you can easily query for required version, like Emacs does in 
configure.in:

pkg-config --exists "gtk+-2.0 >= 2.4 glib-2.0 > 2.4"

In summary, pkg-config is a very helpful tool, but you have to get use to it.

        Jan D.