Re: Emit a warning when -z relro is unsupported

[Florian Weimer <fweimer@redhat.com>]

* Alan Modra via Libc-alpha:

> From 3425515f19d47eb2e13180fe031d94a9c13ce39b Mon Sep 17 00:00:00 2001
> From: Alan Modra <amodra@gmail.com>
> Date: Wed, 29 Jul 2020 16:28:57 +0930
> Subject: Don't mix linker error messages into edited scripts
>
> 	* Makerules (shlib.lds): Discard linker warning output.
> 	(format.lds): Likewise.
>
> diff --git a/Makerules b/Makerules
> index 341db86c7e..ef0fe67d9a 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -557,7 +557,7 @@ $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
>  	$(LINK.o) -shared -Wl,-O1 \
>  		  -nostdlib -nostartfiles \
>  		  $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
> -		  -Wl,--verbose 2>&1 | \
> +		  -Wl,--verbose 2>/dev/null | \
>  	  sed > $@T \
>  	      -e '/^=========/,/^=========/!d;/^=========/d' \
>  	      $(if $(filter yes,$(have-hash-style)), \
> @@ -1073,7 +1073,7 @@ ifneq (unknown,$(output-format))
>  else
>  	$(LINK.o) -shared $(sysdep-LDFLAGS) $(rtld-LDFLAGS) \
>  		  $(LDFLAGS.so) $(LDFLAGS-lib.so) \
> -		  -x c /dev/null -o $@.so -Wl,--verbose -v 2>&1 \
> +		  -x c /dev/null -o $@.so -Wl,--verbose -v 2>/dev/null \
>  	| sed -n -f $< > $@.new
>  	test -s $@.new
>  	rm -f $@.so

This change looks reasonable to me.  Thanks for tracking this down.

We are in the glibc 2.32, so Carlos as the release manager needs to
approve this.

Florian