Re: [Libguestfs] [PATCH nbdkit] golang: Compile against the local nbdkit build, not installed.

On Thu, Apr 23, 2020 at 05:58:25PM +0100, Daniel P. Berrangé wrote: > On Thu, Apr 23, 2020 at 05:55:14PM +0100, Richard W.M. Jones wrote: > > When compiling when an older nbdkit is installed, the build would fail > > because certain symbols such as .get_ready were not defined: > > > > ../../src/libguestfs.org/nbdkit/nbdkit.go:541:8: plugin.get_ready undefined (type _Ctype_struct_nbdkit_plugin has no field or method get_ready) > > > > This happens because we were using the installed <nbdkit-plugin.h> > > rather than the local copy. > > > > We don't want to modify the *.go files themselves as they might be > > copied into other projects. Instead we can set PKG_CONFIG to point to > > a fake pkg-config binary which will return the correct CFLAGS. > > > > Fixes: commit 1ff44288ae1cf95428283e252edd9474c3fe3b55 > > Thanks: Dan Berrangé, Eric Blake > > > +# This fake pkg-config program is used to trick cgo so that > > +# "#cgo pkg-config nbdkit" lines are processed relative to the local > > +# directory and not the installed nbdkit. > > + > > +case "$1" in > > + --cflags*) echo "-I@abs_top_builddir@/include" ;; > > + *) ;; > > +esac > > Don't you need something like this too: > > --libs) echo "-L@abs_top_builddir@/lib -lnbdkit" We don't actually have "libnbdkit". It was proposed a while back but we didn't get sufficient review feedback, and the code was very complex and unmaintainable so it never made it upstream.

cgo currently issues the following two commands: $PKG_CONFIG --cflags -- nbdkit nbdkit nbdkit $PKG_CONFIG --libs -- nbdkit nbdkit nbdkit and yes I also don't know why it prints the package name 3 times.

> The installed nbdkit.pc would do this I presume. Or are you happy relying > on the allow undefined symbols LDFLAGS A "local" nbdkit.pc might indeed be better because we'd be using pkg-config itself to parse the command line.