cross-compilation and proprietary pkg-config replacements (pcre-config, pcap-config, etc)

[John Spencer]

Hello!

I'm currently in the process of adding cross-compilation support to a
linux distribution, but I'm running into a lot of nasty issues.

The #1 offender are proprietary pkg-config replacements, and there are many.
They break cross-compilation by returning non-sysrooted include and
library directories from the host, like -I/usr/include or -L/lib.

I'm glad to say that autoconf itself is one of the few components that
properly handle cross-compilation.

It seems it's "en vogue" for libs to ship their own broken replacement
rather than supplying a portable pkgconfig file...
the list is big, but these here are the most often used ones:
pcap-config, pcre-config, freetype-config, apr-1-config, glib-config,
gtk-config, ncursesw5-config, libmikmod-config, etc.

(in a proper setup those are not even needed, unless they installed
headers into a custom subdir in the standard include path. otherwise
just returning -lmylib is the only thing that's needed.)

since it's unlikely to get any of those fixed in the next decade (or
even convinced to ship .pc files instead of their NIH'd pkg-config
replacement), my idea was to add support for them into autoconf itself:

Offer a m4 macro for each of them (or a generic "external config"
macro), which then calls these config tools and prefixes the returned
include and library paths with the sysroot path (passed to configure via
--with-sysroot=).
so packagers depending on these libraries would use the provided macros
rather than hardcoding their own test.

Does this sound viable and acceptable for inclusion ?
Or is there another workaround that i missed ?

Regards,
--JS

[Wookey]

Post by John Spencer
Hello!
I'm currently in the process of adding cross-compilation support to
a linux distribution, but I'm running into a lot of nasty issues.
The #1 offender are proprietary pkg-config replacements, and there are many.
They break cross-compilation by returning non-sysrooted include and
library directories from the host, like -I/usr/include or -L/lib.
I'm glad to say that autoconf itself is one of the few components
that properly handle cross-compilation.
It seems it's "en vogue" for libs to ship their own broken
replacement rather than supplying a portable pkgconfig file...
pcap-config, pcre-config, freetype-config, apr-1-config,
glib-config, gtk-config, ncursesw5-config, libmikmod-config, etc.

It's not really "en vogue", it's historic: many of the things that
have their own *-config scripts are sufficiently old that they
pre-date pkg-config so are not doing this just to be annoying. At the
time they didn't have much choice.

Post by John Spencer
since it's unlikely to get any of those fixed in the next decade (or
even convinced to ship .pc files instead of their NIH'd pkg-config
replacement),

I don't see why this should be too hard. We've (Debian) already
persuaded a couple of projects to just use pkg-config instead of
whatever homegrown stuff they had, or at least do that as well. It's
the right way to make crossing and multiarch work right (as you are
aware), and I'd hope that most upstreams could be persuaded of that.

But there is a load of work involved in fixing things up and checking
you didn't break all their reverse dependencies so it will take some time.

Post by John Spencer
Offer a m4 macro for each of them (or a generic "external config"
macro), which then calls these config tools and prefixes the
returned include and library paths with the sysroot path (passed to
configure via --with-sysroot=).
so packagers depending on these libraries would use the provided macros
rather than hardcoding their own test.

Interesting idea. Is that easier than just adding a pkg-config file to
each project?

If you do this do remember that we want it to work on multiarch
systems too, where sysroot is not used (equivalent to sysroot=/)

Post by John Spencer
Does this sound viable and acceptable for inclusion ?
Or is there another workaround that i missed ?

Wookey

[Mike Frysinger]

Post by Wookey

Post by John Spencer
It seems it's "en vogue" for libs to ship their own broken
replacement rather than supplying a portable pkgconfig file...
pcap-config, pcre-config, freetype-config, apr-1-config,
glib-config, gtk-config, ncursesw5-config, libmikmod-config, etc.

It's not really "en vogue", it's historic: many of the things that
have their own *-config scripts are sufficiently old that they
pre-date pkg-config so are not doing this just to be annoying. At the
time they didn't have much choice.

at least with some, it's not just a matter of just compile flags. the apr
ones to mind as a complete mess as they use the paths to indirectly look up a
bunch of other things (like use the install libtool linker script). simply
dropping in a .pc file there isn't sufficient to clean up the mess :(.

Post by Wookey

Post by John Spencer
since it's unlikely to get any of those fixed in the next decade (or
even convinced to ship .pc files instead of their NIH'd pkg-config
replacement),

I don't see why this should be too hard. We've (Debian) already
persuaded a couple of projects to just use pkg-config instead of
whatever homegrown stuff they had, or at least do that as well. It's
the right way to make crossing and multiarch work right (as you are
aware), and I'd hope that most upstreams could be persuaded of that.

the gpg guys are the only ones that come to mind as actively ignoring and
blocking progress. i too have had good experience with just about every other
project.
-mike

[Bob Friesenhahn]

Post by Wookey
It's not really "en vogue", it's historic: many of the things that
have their own *-config scripts are sufficiently old that they
pre-date pkg-config so are not doing this just to be annoying. At the
time they didn't have much choice.

Sometimes it is also done because not every system will have
pkg-config, or the one which exists is not well maintained. It can be
done in addition to supporting pkg-config.

Bob

[Mike Frysinger]

Post by Bob Friesenhahn

Post by Wookey
It's not really "en vogue", it's historic: many of the things that
have their own *-config scripts are sufficiently old that they
pre-date pkg-config so are not doing this just to be annoying. At the
time they didn't have much choice.

Sometimes it is also done because not every system will have
pkg-config, or the one which exists is not well maintained. It can be
done in addition to supporting pkg-config.

so build+install a pkg-config ? there are simple replacements that don't
require any external libs like:
https://github.com/pkgconf/pkgconf
-mike

[Werner LEMBERG]

Post by John Spencer
It seems it's "en vogue" for libs to ship their own broken
replacement rather than supplying a portable pkgconfig file... the
pcap-config, pcre-config, freetype-config, apr-1-config,
glib-config, gtk-config, ncursesw5-config, libmikmod-config, etc.

Uh, oh, FreeType provides a .pc file also! And I've fixed all bug
reports w.r.t. freetype-config; in particular, it supports sysroot.
If you think something's still missing, please write a bug report or
provide a patch instead of whining behind my back, so to say :-)


Werner