Re: Checking for -rdynamic flag in gcc/configure

[Ian Lance Taylor <iant at google dot com>]

Steve Ellcey <sje@cup.hp.com> writes:

> I have a question about the check for -rdynamic in gcc/configure.
> What we have in configure.ac is:
>
>   # Check -rdynamic
>   LDFLAGS="$LDFLAGS -rdynamic"
>   AC_MSG_CHECKING([for -rdynamic])
>   AC_TRY_LINK([],[return 0;],
>     [AC_MSG_RESULT([yes]); have_rdynamic=yes],
>     [AC_MSG_RESULT([no])])
>   if test x"$have_rdynamic" = x"yes" ; then
>     pluginlibs="-rdynamic"
>   fi
>
> The problem I have is that on HP-UX this test will set have_rdynamic
> to yes even though the HP linker doesn't understand the option.
> The AC_TRY_LINK works because the linker prints a warning message
> about not understanding -rdynamic but still runs and creates an
> object file.  Thus the configure script thinks the HP linker does
> know about the -rdynamic flag and continues to use it (resulting
> in more warnings during the GCC build).
>
> Any ideas on how to address this?

Link a small program with -rdynamic, one which defines a globally
visible function which is not called.  Run objdump -T and see if you can
see that symbol in the output.

If you follow this path you must do the in_tree_ld/ld_ver dance so that
cross-compilers continue to work.

Or, run ld --help and look for --export-dynamic.

Ian