I write a m4 macro and in this macro I try to detect
a library with AC_CHECK_LIB.
AC_CHECK_LIB($ax_lib, main, ...)
where ax_lib is my library.
The check fails because the generated code does not link
against the library.
I catched the generated code from the configure script,
tried to compile it and the linker reveals the reason:

/usr/local/lib/libboost_unit_test_framework.so: undefined reference to `init
_unit_test_suite(int, char**)'
collect2: ld returned 1 exit status

libboost_unit_test_framework.so is my lib ($ax_lib) and this lib
requires some other code.

How is it possible to check the library ?

I have only the idea to look if the library axist as file in my lib-director
y.
But is there a better solution ?

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gelbeiche <borstel@fliegenpilz.de> writes:

> I write a m4 macro and in this macro I try to detect
> a library with AC_CHECK_LIB.
> AC_CHECK_LIB($ax_lib, main, ...)
> where ax_lib is my library.
> The check fails because the generated code does not link
> against the library.

If you are using a C++ library, as the post implies, try something
along these lines to check if it's possible to instantiate a class
from the library:

saved_ldflags="${LDFLAGS}"
LDFLAGS="${LDFLAGS} -lboost_program_options"
AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <boost/program_options.hpp
>],
& #91;boost::program_options::variables_ma
p::variables_map dummy()])],
[AC_MSG_RESULT([yes])
BOOST_LIBS="-lboost_program_options"],
[AC_MSG_RESULT([no])
AC_MSG_FAILURE([libboost_program_options (Boost C++ Libraries) is not in
stalled, but is required by $PACKAGE])])
LDFLAGS="${saved_ldflags}"
AC_SUBST([BOOST_LIBS])

If you are doing it properly, you'd also replace the '#' with a
quadrigraph, though in this case it doesn't appear to be strictly
required.  If you are mixing languages, you also want to wrap that
with AC_LANG_PUSH and AC_LANG_POP to make sure it uses the C++
variants of those macros.


Regards,
Roger

- --
Roger Leigh
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Roger Leigh <${rleigh}@invalid.whinlatter.ukfsn.org.invalid> writes:

> gelbeiche <borstel@fliegenpilz.de> writes:
> 
>
> If you are using a C++ library, as the post implies, try something
> along these lines to check if it's possible to instantiate a class
> from the library:
>
> saved_ldflags="${LDFLAGS}"
> LDFLAGS="${LDFLAGS} -lboost_program_options"
> AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <boost/program_options.h
pp>],
>                                & #91;boost::program_options::variables_ma
p:
:variables_map dummy()])],
>                [AC_MSG_RESULT([yes])
> 	        BOOST_LIBS="-lboost_program_options"],
>                [AC_MSG_RESULT([no])
> 	        AC_MSG_FAILURE([libboost_program_options (Boost C++ Libraries
) is not installed, but is required by $PACKAGE])])
> LDFLAGS="${saved_ldflags}"
> AC_SUBST([BOOST_LIBS])
>
> If you are doing it properly, you'd also replace the '#' with a
> quadrigraph, though in this case it doesn't appear to be strictly
> required.  If you are mixing languages, you also want to wrap that
> with AC_LANG_PUSH and AC_LANG_POP to make sure it uses the C++
> variants of those macros.
>

Good hint ! This is the way I go now.

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