bug#21106: AC_SUBST([FOO_LIB], ['libfoo.la']) breaks dependency checker

[Stanislav Brabec]

I just wanted to make an option to link the program either against
in-package instance or external instance.

To make things as easy as possible, I wanted to define FOO_LIB in
configure.ac either as 'libfoo.la' or '-lfoo' using e. g.:

AC_SUBST([FOO_LIB], ['libfoo.la'])

and then in Makefile.am use just:

myprogram_LDADD = $(FOO_LIB)

Everything works well except parallel build. It seems that dependency
checker is not able to see such dependency, and if I try to compile the
project with "make -j7", it fails:

libtool:   error: cannot find the library 'libfoo.la' or unhandled argument 
'libfoo.la'

Plain "make" works.

Is it a bug or expected behavior?

Is there any better way how to do such things than use

if USE_BUILTIN_LIBFOO
myprogram_LDADD = libfoo.la
else
myprogram_LDADD = -lfoo
endif

everywhere I need to link with libfoo?

Attaching a minimalistic example.

-- 
Best Regards / S pozdravem,

Stanislav Brabec
software developer
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libfoo.tar.gz
Description: application/gzip