On Friday 07 December 2007, Stepan Kasal wrote:
> 1)
> The most important one is this:
>
> $ pkg-config --libs blkid
> -L/lib -lblkid -luuid -ldevmapper
>
> The "-ldevmapper" option is not only redundant, it's very evil.
> Se below for a detailed explanation (let's call this "so-deps hell").
>
> Karel proposes to add --as-needed (or -Wl,--as-needed) to *_LDFLAGS
> for dynamic linking to fix this. (configure has to check that
> --as-needed is available, of course.)
>
> My proposal would be to use hardwired "-lblkid -luuid" for dynamic
> linking and start using pkg-config only when/if it is really needed,
> ie. a real-world bug report arrives.
i learned about a new option in .pc files which i think the blkid.pc provider
should be fixed to use:
Libs: -L${libdir} -lblkid
Libs.private: -luuid -ldevmapper
so now when you run `pkg-config --libs`, you get the normal thing of
just "-Llib -lblkid" which is what we want. if you need to do static
linking, just use `pkg-config --libs --static` and you'll get a full list of
libraries which are needed when you do static linking.
i think this addresses the ugly excessive SONAME propagation ("so-dep hell")
and alleviates the need for --as-needed at all.
> 2)
> Second problem:
> As a disiplined citizen of the Automake world, you should put -l and
> -L options to *_LDADD and the rest to *_LDFLAGS.
> Though the pkg-config script has options which enable to solve this,
> Autoconf macros in pkg.m4 do not use them.
> One has to do something like:
> BLKID_LDADD=$(pkg-config --libs-only-l blkid)" "$(pkg-config --libs-only-L
> blkid) BLKID_LDFLAGS=$(pkg-config --libs-only-other blkid)
>
> It's a question whether the pkg.m4 macros should be used in
> configure.ac, or whether they shall serve only as an inspiration for
> our code. Roughly speaking, we would call
> AC_RUN_LOG([pkg-config --exists --print-errors blkid])
> and check whether the --libs-only-* options are supported before the
> above assignments.
> But Karel suggests we use PKG_CHECK_EXISTS from pkg.m4 for this (that
> would include a version number check to ensure --libs-only-* are
> available).
>
> Yes, this cries for a fix in pkg.m4, but the fact that the old
> broken interface has to be maintained may complicate the situation...
an optional additional argument to the PKG_CHECK_EXISTS macro that, when not
provided gives old behavior and when provided, controls the newer proper
behavior ?
since this sounds like architectual issues, i think the best route would be
parallel ones:
- have a local pkg.m4 that does what we need
- engage with pkg-config maintainers to see if we can drive the direction
-mike
Attachment:
signature.asc
Description: This is a digitally signed message part.
