Re: [PATCH] Do not use --hash-style=both for building glibc shared objects

[Carlos O'Donell <carlos@redhat.com>]

On 4/29/22 03:00, Florian Weimer via Libc-alpha wrote:
> The comment indicates that --hash-style=both was used to maintain
> compatibility with static dlopen, but we had many internal ABI
> changes since then, so this compatiblity does not add value anymore.
> 
> Tested on i686-linux-gnu and x86_64-linux-gnu.  Built with
> build-many-glibcs.py.

Agreed. We absolutely don't need --hash-style=both, and even today I'd like to
see us phase out the old hash at some point.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
 
> ---
>  Makeconfig     |  9 ---------
>  Makerules      |  7 -------
>  config.make.in |  1 -

OK. That matches the 3 files that need changing.

>  configure      | 28 ----------------------------
>  configure.ac   | 16 ----------------
>  5 files changed, 61 deletions(-)
> 
> diff --git a/Makeconfig b/Makeconfig
> index 0aa5fb0099..760f14e92f 100644
> --- a/Makeconfig
> +++ b/Makeconfig
> @@ -362,15 +362,6 @@ relro-LDFLAGS = -Wl,-z,relro
>  LDFLAGS.so += $(relro-LDFLAGS)
>  LDFLAGS-rtld += $(relro-LDFLAGS)
>  
> -ifeq (yes,$(have-hash-style))
> -# For the time being we unconditionally use 'both'.  At some time we
> -# should declare statically linked code as 'out of luck' and compile
> -# with --hash-style=gnu only.
> -hashstyle-LDFLAGS = -Wl,--hash-style=both
> -LDFLAGS.so += $(hashstyle-LDFLAGS)
> -LDFLAGS-rtld += $(hashstyle-LDFLAGS)
> -endif
> -

OK.

>  ifeq (no,$(build-pie-default))
>  pie-default = $(no-pie-ccflag)
>  else # build-pie-default
> diff --git a/Makerules b/Makerules
> index 428464f092..354528b8c7 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -557,13 +557,6 @@ $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
>  		  -Wl,--verbose 2>/dev/null | \
>  	  sed > $@T \
>  	      -e '/^=========/,/^=========/!d;/^=========/d' \
> -	      $(if $(filter yes,$(have-hash-style)), \
> -		   -e 's/^.*\.gnu\.hash[ 	]*:.*$$/  .note.ABI-tag : { *(.note.ABI-tag) } &/' \
> -		   -e '/^[ 	]*\.hash[ 	]*:.*$$/{h;d;}' \
> -		   -e '/DATA_SEGMENT_ALIGN/{H;g}' \
> -		, \
> -		   -e 's/^.*\.hash[ 	]*:.*$$/  .note.ABI-tag : { *(.note.ABI-tag) } &/' \
> -	       ) \

OK. Remove filter.

>  	      -e 's/^.*\*(\.dynbss).*$$/& \
>  		 PROVIDE(__start___libc_freeres_ptrs = .); \
>  		 *(__libc_freeres_ptrs) \
> diff --git a/config.make.in b/config.make.in
> index bf728c71c0..fff4c78dd0 100644
> --- a/config.make.in
> +++ b/config.make.in
> @@ -70,7 +70,6 @@ have-libcap = @have_libcap@
>  have-cc-with-libunwind = @libc_cv_cc_with_libunwind@
>  fno-unit-at-a-time = @fno_unit_at_a_time@
>  bind-now = @bindnow@
> -have-hash-style = @libc_cv_hashstyle@
>  use-default-link = @use_default_link@
>  have-cxx-thread_local = @libc_cv_cxx_thread_local@
>  have-loop-to-function = @libc_cv_cc_loop_to_function@
> diff --git a/configure b/configure
> index 5a730dc5fc..716dc041b6 100755
> --- a/configure
> +++ b/configure
> @@ -622,7 +622,6 @@ libc_cv_cc_nofma
>  libc_cv_mtls_dialect_gnu2
>  fno_unit_at_a_time
>  libc_cv_has_glob_dat
> -libc_cv_hashstyle
>  libc_cv_fpie
>  libc_cv_z_execstack
>  ASFLAGS_config
> @@ -6194,33 +6193,6 @@ $as_echo "$libc_cv_fpie" >&6; }
>  
>  
>  
> -{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --hash-style option" >&5
> -$as_echo_n "checking for --hash-style option... " >&6; }
> -if ${libc_cv_hashstyle+:} false; then :
> -  $as_echo_n "(cached) " >&6
> -else
> -  cat > conftest.c <<EOF
> -int _start (void) { return 42; }
> -EOF
> -if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> -			    -fPIC -shared -o conftest.so conftest.c
> -			    -Wl,--hash-style=both -nostdlib 1>&5'
> -  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> -  (eval $ac_try) 2>&5
> -  ac_status=$?
> -  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> -  test $ac_status = 0; }; }
> -then
> -  libc_cv_hashstyle=yes
> -else
> -  libc_cv_hashstyle=no
> -fi
> -rm -f conftest*
> -fi
> -{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_hashstyle" >&5
> -$as_echo "$libc_cv_hashstyle" >&6; }
> -
> -
>  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for GLOB_DAT reloc" >&5
>  $as_echo_n "checking for GLOB_DAT reloc... " >&6; }
>  if ${libc_cv_has_glob_dat+:} false; then :
> diff --git a/configure.ac b/configure.ac
> index a045f6608e..d08ad4d64e 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -1360,22 +1360,6 @@ LIBC_TRY_CC_OPTION([-fpie], [libc_cv_fpie=yes], [libc_cv_fpie=no])
>  
>  AC_SUBST(libc_cv_fpie)
>  
> -AC_CACHE_CHECK(for --hash-style option,
> -	       libc_cv_hashstyle, [dnl
> -cat > conftest.c <<EOF
> -int _start (void) { return 42; }
> -EOF
> -if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> -			    -fPIC -shared -o conftest.so conftest.c
> -			    -Wl,--hash-style=both -nostdlib 1>&AS_MESSAGE_LOG_FD])
> -then
> -  libc_cv_hashstyle=yes
> -else
> -  libc_cv_hashstyle=no
> -fi
> -rm -f conftest*])
> -AC_SUBST(libc_cv_hashstyle)
> -

OK.

>  AC_CACHE_CHECK(for GLOB_DAT reloc,
>  	       libc_cv_has_glob_dat, [dnl
>  cat > conftest.c <<EOF
> 


-- 
Cheers,
Carlos.