build-shlib-helper reporting of undefined symbols

[David Holsgrove <david dot holsgrove at xilinx dot com>]

Hi,

I'm in the process of submitting a MicroBlaze port to libc-ports, and I find
that like other architectures, I'm explicitly linking with ld.so for a number
of the libraries in my target's Makefile to resolve undefined symbols.

Joseph Myer asked that I raise the question here as I'm not familiar enough
with glibc's core Make infrastructure to be sure that any out of tree fix I
have would be safe for all ports.

I have seen anecdotally that removing the linker command '-z,defs' in the
build-shlib-helper (diff below) allows me to successfully build a functional
MicroBlaze toolchain without requiring any of the explicit ld.so links.


diff --git a/Makerules b/Makerules
index d88bb62..a5b4528 100644
--- a/Makerules
+++ b/Makerules
@@ -441,8 +441,7 @@ lib%.so: lib%_pic.a $(+preinit) $(+postinit) $(+interp)
        $(build-shlib)

 define build-shlib-helper
-$(LINK.o) -shared $(static-libgcc) -Wl,-O1 $(sysdep-LDFLAGS) \
-         $(if $($(@F)-no-z-defs)$(no-z-defs),,-Wl,-z,defs) $(rtld-LDFLAGS) \
+$(LINK.o) -shared $(static-libgcc) -Wl,-O1 $(sysdep-LDFLAGS) $(rtld-LDFLAGS) \
          $(extra-B-$(@F:lib%.so=%).so) -B$(csu-objpfx) \
          $(extra-B-$(@F:lib%.so=%).so) $(load-map-file) \
          -Wl,-soname=lib$(libprefix)$(@F:lib%.so=%).so$($(@F)-version) \


What is the purpose of this warning for unresolved symbols, and could this be
safely removed at this level?


Alternatively, Joseph had suggested that a group with --as-needed ld.so for each
shared library link might be the best option;

>I think we should make all the miscellaneous shared libraries and .so 
>files be linked more like normal libraries linked with a shared glibc 
>after installation.  That is, --start-group libc.so libc_nonshared.a 
>--as-needed ld.so --no-as-needed --end-group.  And with that change, 
>remove all the miscellaneous rules in various makefiles (sysdeps and 
>otherwise) to link this or that library with ld.so or libc_nonshared.a.

If this was to be done, where would be the right place to do it?

thanks,
David