Re: [PATCH] Makerules/Makeconfig: Add rtlddir-build for the libc.so loader reference

"Andreas K. Huettel" <[email protected]> Wed, 15 Jul 2026 20:30:37 +0900
Newsgroups	gmane.comp.lib.glibc.alpha
Organization	Gentoo Linux
Message-ID	<[email protected]>
Am Sonntag, 12. Juli 2026, 07:20:53 Japanische Normalzeit schrieb Tiago Dinis:
> From: Tiago Dinis <[email protected]>
> 
> The libc.so linker script generated by "make install" references the
> dynamic linker via an AS_NEEDED entry so the linker can resolve it
> while building against libc.  Previously this used \$(rtlddir), which
> is also the path compiled into ld-linux as its self-identification
> string (-DRTLD in elf/Makefile) and used for the PT_INTERP of glibc's
> own binaries (installed-rtld-LDFLAGS in Makeconfig).
> 
> These two uses legitimately differ when glibc is built to run on a
> different environment with a different filesystem structure than the
> build system: the loader is installed under the build tree, but the
> resulting binaries must reference it via the runtime path of the
> target environment.  Setting \$(rtlddir) to that runtime path makes
> libc.so point at a loader that is not present at build time, breaking
> linking against libc and later consumers such as binutils.
> 
> Introduce \$(rtlddir-build), defaulting to \$(rtlddir), and use it for
> the libc.so AS_NEEDED entry so it tracks where the loader is actually
> installed.  \$(rtlddir) keeps driving the runtime path
> (self-identification and PT_INTERP).  This is a no-op for the default
> configuration, where rtlddir-build == rtlddir == slibdir.
> 

Not urgent, after release (if it gets RB)

> Reviewed-by: (none yet)
> ---
>  Makeconfig | 9 +++++++++
>  Makerules  | 2 +-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/Makeconfig b/Makeconfig
> index e7dbd9fb..135a98b6 100644
> --- a/Makeconfig
> +++ b/Makeconfig
> @@ -165,6 +165,15 @@ rtlddir = $(slibdir)
>  endif
>  inst_rtlddir = $(install_root)$(rtlddir)
>  
> +# Directory referenced by the libc.so linker script (AS_NEEDED entry) for
> +# the dynamic linker at build time.  This points at the location where the
> +# loader is actually installed so the linker can resolve it while building
> +# against libc.  It defaults to rtlddir (where it differs, the loader is
> +# installed in rtlddir-build but identified/loaded at runtime via rtlddir).
> +ifndef rtlddir-build
> +rtlddir-build = $(rtlddir)
> +endif
> +
>  # Prefix to put on files installed in $(libdir).  For libraries `libNAME.a',
>  # the prefix is spliced between `lib' and the name, so the linker switch
>  # `-l$(libprefix)NAME' finds the library; for other files the prefix is
> diff --git a/Makerules b/Makerules
> index 6bef57ec..61b24131 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -1024,7 +1024,7 @@ $(inst_libdir)/libc.so: $(common-objpfx)format.lds \
>  	 cat $<; \
>  	 echo 'GROUP ( $(slibdir)/libc.so$(libc.so-version)' \
>  	      '$(libdir)/$(patsubst %,$(libtype.oS),$(libprefix)$(libc-name))'\
> -	      ' AS_NEEDED (' $(rtlddir)/$(rtld-installed-name) ') )' \
> +	      ' AS_NEEDED (' $(rtlddir-build)/$(rtld-installed-name) ') )' \
>  	) > [email protected]
>  	mv -f [email protected] $@
>  
> 


-- 
PD Dr. Andreas K. Hüttel
[email protected]
Gentoo Linux developer 
(council, comrel, toolchain, base-system, perl, libreoffice)
https://wiki.gentoo.org/wiki/User:Dilfridge
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