[4/4] Install shared objects under their ABI names

  Previously, the installed objects were named like libc-2.33.so,
and the ABI soname libc.so.6 was just a symbolic link.

The Makefile targets to install these symbolic links are no longer
needed after this, so they are removed with this commit.  The more
general $(make-link) command (which invokes scripts/rellns-sh) is
retained because other symbolic links are still needed.
---
 INSTALL      | 10 ++++++++++
 Makefile     |  6 ------
 Makerules    | 45 +++++----------------------------------------
 NEWS         |  8 ++++++++
 elf/Makefile | 10 ++--------
 5 files changed, 25 insertions(+), 54 deletions(-)
  

On 6/10/21 4:23 AM, Florian Weimer via Libc-alpha wrote:
> Previously, the installed objects were named like libc-2.33.so,
> and the ABI soname libc.so.6 was just a symbolic link.

This patch contains INSTALL changes which should not be here and I expect
were left over from your previous patch. Please drop them. Because you 
are *only* dropping the edits to that file you can commit as-is without
a v2. So I'm providing a review here.
 
> The Makefile targets to install these symbolic links are no longer
> needed after this, so they are removed with this commit.  The more
> general $(make-link) command (which invokes scripts/rellns-sh) is
> retained because other symbolic links are still needed.

No regressions on x86_64 and i686. Installed files look good.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@rehdat.com>

> ---
>  INSTALL      | 10 ++++++++++

Drop this.

>  Makefile     |  6 ------
>  Makerules    | 45 +++++----------------------------------------
>  NEWS         |  8 ++++++++
>  elf/Makefile | 10 ++--------
>  5 files changed, 25 insertions(+), 54 deletions(-)
> 
> diff --git a/INSTALL b/INSTALL
> index bc761ab98b..ed5f66489b 100644
> --- a/INSTALL
> +++ b/INSTALL

Drop this change from this file.

> @@ -199,6 +199,16 @@ if 'CFLAGS' is specified it must enable optimization.  For example:
>       RELRO and a read-only global offset table (GOT), at the cost of
>       slightly increased program load times.
>  
> +'--disable-major-minor-libraries'
> +     Do not install shared objects under file names that contain the
> +     major and minor version of the GNU C Library.  By default, such
> +     names are used, and the names defined by the ABI are provided as
> +     symbolic links only.  This causes problems with certain package
> +     managers during library upgrades and (in particular) downgrades, so
> +     this option can be used to install these shared objects directly
> +     under their ABI-defined names, without an additional indirection
> +     via symbolic links.
> +
>  '--enable-pt_chown'
>       The file 'pt_chown' is a helper binary for 'grantpt' (*note
>       Pseudo-Terminals: Allocation.) that is installed setuid root to fix
> diff --git a/Makefile b/Makefile
> index 242d36de91..c115c652a0 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -109,12 +109,6 @@ elf/ldso_install:
>  # Ignore the error if we cannot update /etc/ld.so.cache.
>  ifeq (no,$(cross-compiling))
>  ifeq (yes,$(build-shared))
> -install: install-symbolic-link
> -.PHONY: install-symbolic-link
> -install-symbolic-link: subdir_install
> -	$(symbolic-link-prog) $(symbolic-link-list)
> -	rm -f $(symbolic-link-list)
> -

OK.

>  install:
>  	-test ! -x $(elf-objpfx)ldconfig || LC_ALL=C \
>  	  $(elf-objpfx)ldconfig $(addprefix -r ,$(install_root)) \
> diff --git a/Makerules b/Makerules
> index d3f29d0b89..6efff78fbe 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -989,14 +989,12 @@ versioned := $(strip $(foreach so,$(install-lib.so),\
>  install-lib.so-versioned := $(filter $(versioned), $(install-lib.so))
>  install-lib.so-unversioned := $(filter-out $(versioned), $(install-lib.so))
>  
> -# For libraries whose soname have version numbers, we install three files:
> +# For libraries whose soname have version numbers, we install two files:

OK.

>  #	$(inst_libdir)/libfoo.so	-- for linking, symlink or ld script
> -#	$(inst_slibdir)/libfoo.so.NN	-- for loading by SONAME, symlink
> -#	$(inst_slibdir)/libfoo-X.Y.Z.so -- the real shared object file
> +#	$(inst_slibdir)/libfoo.so.NN	-- for loading by SONAME

OK.

>  install-lib-nosubdir: $(install-lib.so-unversioned:%=$(inst_slibdir)/%) \
>  		      $(foreach L,$(install-lib.so-versioned),\
>  				$(inst_libdir)/$L \
> -				$(inst_slibdir)/$(L:.so=)-$(version).so \

OK.

>  				$(inst_slibdir)/$L$($L-version))
>  
>  # Install all the unversioned shared libraries.
> @@ -1029,35 +1027,10 @@ ln -f $(objpfx)/$(@F) $@
>  endef
>  endif
>  
> -ifeq (yes,$(build-shared))
> -ifeq (no,$(cross-compiling))
> -symbolic-link-prog := $(elf-objpfx)sln
> -symbolic-link-list := $(elf-objpfx)symlink.list
> -define make-shlib-link
> -echo `$(..)scripts/rellns-sh -p $< $@` $@ >> $(symbolic-link-list)
> -endef
> -else # cross-compiling
> -# We need a definition that can be used by elf/Makefile's install rules.
> -symbolic-link-prog = $(LN_S)
> -endif
> -endif
> -ifndef make-shlib-link
> -define make-shlib-link
> -rm -f $@
> -$(LN_S) `$(..)scripts/rellns-sh -p $< $@` $@
> -endef
> -endif

OK.

> -
>  ifdef libc.so-version
> -# For a library specified to be version N, install three files:
> -# libc.so	->	libc.so.N	(e.g. libc.so.6)
> -# libc.so.6	->	libc-VERSION.so	(e.g. libc-1.10.so)
> -
> -$(inst_slibdir)/libc.so$(libc.so-version): $(inst_slibdir)/libc-$(version).so \
> -					   $(+force)
> -	$(make-shlib-link)
> -$(inst_slibdir)/libc-$(version).so: $(common-objpfx)libc.so $(+force)

OK.

> +$(inst_slibdir)/libc.so$(libc.so-version): $(common-objpfx)libc.so $(+force)
>  	$(do-install-program)
> +
>  install: $(inst_slibdir)/libc.so$(libc.so-version)
>  
>  # This fragment of linker script gives the OUTPUT_FORMAT statement
> @@ -1125,15 +1098,7 @@ include $(o-iterator)
>  generated += $(foreach o,$(versioned),$o$($o-version))
>  
>  define o-iterator-doit
> -$(inst_slibdir)/$o$($o-version): $(inst_slibdir)/$(o:.so=)-$(version).so \
> -				 $(+force);
> -	$$(make-shlib-link)
> -endef
> -object-suffixes-left := $(versioned)
> -include $(o-iterator)
> -
> -define o-iterator-doit
> -$(inst_slibdir)/$(o:.so=)-$(version).so: $(objpfx)$o $(+force);
> +$(inst_slibdir)/$o$($o-version): $(objpfx)$o $(+force);
>  	$$(do-install-program)

OK.

>  endef
>  object-suffixes-left := $(versioned)
> diff --git a/NEWS b/NEWS
> index 1bf3daa502..1634e20ce5 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -48,6 +48,14 @@ Deprecated and removed features, and other changes affecting compatibility:
>  * The function pthread_yield has been deprecated; programs should use
>    the equivalent standard function sched_yield instead.
>  
> +* Previously, glibc installed its various shared objects under versioned
> +  file names such as libc-2.33.so.  The ABI sonames (e.g., libc.so.6)
> +  were provided as symbolic links.  Starting with glibc 2.34, the shared
> +  objects are installed under their ABI sonames directly, without
> +  symbolic links.  This increases compatibility with distribution
> +  package managers that delete removed files late during the package
> +  upgrade or downgrade process.

OK. I agree, the new glibc is present immediately at unpack time with a scheme
that keeps the new glibc always as libc.so.6. It is simpler and easier to
reason about when it comes to package management.

> +
>  Changes to build and runtime requirements:
>  
>  * On Linux, the shm_open, sem_open, and related functions now expect the
> diff --git a/elf/Makefile b/elf/Makefile
> index 1751f5ec67..02f634c192 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -628,20 +628,14 @@ $(objpfx)trusted-dirs.st: Makefile $(..)Makeconfig
>  CPPFLAGS-dl-load.c += -I$(objpfx). -I$(csu-objpfx).
>  
>  ifeq (yes,$(build-shared))
> -$(inst_slibdir)/$(rtld-version-installed-name): $(objpfx)ld.so $(+force)
> +$(inst_rtlddir)/$(rtld-installed-name): $(objpfx)ld.so $(+force)

OK.

>  	$(make-target-directory)
>  	$(do-install-program)
>  
> -$(inst_rtlddir)/$(rtld-installed-name): \
> -  $(inst_slibdir)/$(rtld-version-installed-name) \
> -  $(inst_slibdir)/libc-$(version).so
> -	$(make-target-directory)
> -	$(make-shlib-link)
> -

OK.

>  # Special target called by parent to install just the dynamic linker.
>  .PHONY: ldso_install
>  ldso_install: $(inst_rtlddir)/$(rtld-installed-name)
> -endif
> +endif # $(build-shared)
>  
>  
>  # Workarounds for ${exec_prefix} expansion in configure variables.
>