On Thu, Nov 18, 2021 at 10:23:41PM +0100, Mark Wielaard wrote: > dwfl-proc-attach uses (overrides) dlopen (so it does nothing). This > seems to cause a versioned dlopen symbol to be pulled in when building > with LTO. Resulting in a link failure (when dlopen isn't integrated > into libc): > > /usr/bin/ld: dwfl-proc-attach.o (symbol from plugin): undefined > reference to symbol 'dlopen@@GLIBC_2.2.5' > /usr/bin/ld: /usr/lib64/libdl.so.2: error adding symbols: DSO missing > from command line collect2: error: ld returned 1 exit status > > So simply explicitly add -ldl to the LDFLAGS. > > Signed-off-by: Mark Wielaard <m...@klomp.org> > --- > tests/ChangeLog | 4 ++++ > tests/Makefile.am | 2 +- > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/tests/ChangeLog b/tests/ChangeLog > index a59cdd51..97cb3fa3 100644 > --- a/tests/ChangeLog > +++ b/tests/ChangeLog > @@ -1,3 +1,7 @@ > +2021-11-18 Mark Wielaard <m...@klomp.org> > + > + * Makefile.am (dwfl_proc_attach_LDFLAGS): Add -ldl. > + > 2021-11-05 Frank Ch. Eigler <f...@redhat.com> > > PR28430 > diff --git a/tests/Makefile.am b/tests/Makefile.am > index bfb8b13a..f212f9fb 100644 > --- a/tests/Makefile.am > +++ b/tests/Makefile.am > @@ -717,7 +717,7 @@ strptr_LDADD = $(libelf) > newdata_LDADD = $(libelf) > elfstrtab_LDADD = $(libelf) > dwfl_proc_attach_LDADD = $(libdw) > -dwfl_proc_attach_LDFLAGS = -pthread $(AM_LDFLAGS) > +dwfl_proc_attach_LDFLAGS = -pthread -ldl $(AM_LDFLAGS)
Let's make clear what's going on here. First of all, dwfl-proc-attach.c does not use dlopen so it doesn't pull it in and doesn't need -ldl. In regular builds, dwfl-proc-attach.o is linked with ../libdw/libdw.so which in turn uses dlopen and is already linked with -ldl. When elfutils is configured with --enable-gprof or --enable-gcov, BUILD_STATIC is enabled and dwfl-proc-attach.o is linked with ../libdw/libdw.a -lz $(zip_LIBS) $(libelf) $(libebl) -ldl -lpthread which already contains -ldl. In any case, I fail to understand why dwfl-proc-attach might need an extra -ldl, especially in LDFLAGS which goes before LDADD in the linking command. -- ldv
