Re: [PATCH v5] Set the retain attribute on _elf_set_element if CC supports [BZ #27492]

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Apr 6, 2021 at 2:46 PM Fangrui Song <maskray@google.com> wrote:
>
>
> On 2021-04-05, H.J. Lu wrote:
> >On Mon, Apr 5, 2021 at 2:03 PM Fangrui Song <maskray@google.com> wrote:
> >>
> >> On 2021-04-05, H.J. Lu wrote:
> >> >On Mon, Apr 5, 2021 at 11:17 AM Fangrui Song <maskray@google.com> wrote:
> >> >>
> >> >> On 2021-04-04, H.J. Lu wrote:
> >> >> >On Sat, Apr 3, 2021 at 2:57 PM Fangrui Song <maskray@google.com> wrote:
> >> >> >>
> >> >> >> On 2021-04-03, H.J. Lu wrote:
> >> >> >> >On Sat, Apr 3, 2021 at 11:02 AM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> On 2021-04-02, H.J. Lu wrote:
> >> >> >> >> >On Thu, Apr 1, 2021 at 8:23 PM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >> >>
> >> >> >> >> >> On 2021-04-01, H.J. Lu wrote:
> >> >> >> >> >> >On Wed, Mar 31, 2021 at 6:07 PM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >> >> >>
> >> >> >> >> >> >> So that text_set_element/data_set_element/bss_set_element defined
> >> >> >> >> >> >> variables will be retained by the linker.
> >> >> >> >> >> >>
> >> >> >> >> >> >> Note: 'used' and 'retain' are orthogonal: 'used' makes sure the variable
> >> >> >> >> >> >> will not be optimized out; 'retain' prevents section garbage collection
> >> >> >> >> >> >> if the linker support SHF_GNU_RETAIN.
> >> >> >> >> >> >>
> >> >> >> >> >> >> GNU ld 2.37 and LLD 13 will support -z start-stop-gc which allow C
> >> >> >> >> >> >> identifier name sections to be GCed even if there are live
> >> >> >> >> >> >> __start_/__stop_ references.
> >> >> >> >> >> >>
> >> >> >> >> >> >> Without the change, there are some static linking problems, e.g.
> >> >> >> >> >> >> _IO_cleanup (libio/genops.c) may be discarded by ld --gc-sections, so
> >> >> >> >> >> >> stdout is not flushed on exit.
> >> >> >> >> >> >>
> >> >> >> >> >> >> Note: GCC may warning ‘retain’ attribute ignored while __has_attribute(retain) is 1
> >> >> >> >> >> >> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99587).
> >> >> >> >> >> >> ---
> >> >> >> >> >> >> Changes in v1 -> v2:
> >> >> >> >> >> >> * Define attribute_used_retain_section
> >> >> >> >> >> >> Changes in v2 -> v3:
> >> >> >> >> >> >> * Use attribute_used_retain instead attribute_used_retain_section
> >> >> >> >> >> >> Changes in v3 -> v4:
> >> >> >> >> >> >> * Add LIBC_LINKER_FEATURE detection for -z start-stop-gc and add tst-cleanup* tests
> >> >> >> >> >> >> Changes in v4 -> v5:
> >> >> >> >> >> >> * Enable -z start-stop-gc tests if both retain and -z start-stop-gc are supported
> >> >> >> >> >> >> * Rename *gcc_retain* to *gnu_retain*
> >> >> >> >> >> >> ---
> >> >> >> >> >> >>  config.h.in            |  3 +++
> >> >> >> >> >> >>  configure              | 59 ++++++++++++++++++++++++++++++++++++++++++
> >> >> >> >> >> >>  configure.ac           | 21 +++++++++++++++
> >> >> >> >> >> >>  include/libc-symbols.h | 14 +++++++---
> >> >> >> >> >> >>  libio/Makefile         | 32 +++++++++++++++++++++++
> >> >> >> >> >> >>  libio/tst-cleanup.c    | 33 +++++++++++++++++++++++
> >> >> >> >> >> >>  libio/tst-cleanup.exp  |  1 +
> >> >> >> >> >> >>  7 files changed, 159 insertions(+), 4 deletions(-)
> >> >> >> >> >> >>  create mode 100644 libio/tst-cleanup.c
> >> >> >> >> >> >>  create mode 100644 libio/tst-cleanup.exp
> >> >> >> >> >> >>
> >> >> >> >> >> >> diff --git a/config.h.in b/config.h.in
> >> >> >> >> >> >> index ca1547ae67..96a08c7757 100644
> >> >> >> >> >> >> --- a/config.h.in
> >> >> >> >> >> >> +++ b/config.h.in
> >> >> >> >> >> >> @@ -187,6 +187,9 @@
> >> >> >> >> >> >>  /* Define if gcc supports attribute ifunc.  */
> >> >> >> >> >> >>  #undef HAVE_GCC_IFUNC
> >> >> >> >> >> >>
> >> >> >> >> >> >> +/* Define if CC supports attribute retain.  */
> >> >> >> >> >> >> +#undef HAVE_GNU_RETAIN
> >> >> >> >> >> >> +
> >> >> >> >> >> >>  /* Define if the linker defines __ehdr_start.  */
> >> >> >> >> >> >>  #undef HAVE_EHDR_START
> >> >> >> >> >> >>
> >> >> >> >> >> >> diff --git a/configure b/configure
> >> >> >> >> >> >> index fcf43bf7de..e64b7f8efe 100755
> >> >> >> >> >> >> --- a/configure
> >> >> >> >> >> >> +++ b/configure
> >> >> >> >> >> >> @@ -4105,6 +4105,31 @@ fi
> >> >> >> >> >> >>  $as_echo "$libc_cv_textrel_ifunc" >&6; }
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >> +# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
> >> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for GNU attribute retain support" >&5
> >> >> >> >> >> >> +$as_echo_n "checking for GNU attribute retain support... " >&6; }
> >> >> >> >> >> >> +if ${libc_cv_gnu_retain+:} false; then :
> >> >> >> >> >> >> +  $as_echo_n "(cached) " >&6
> >> >> >> >> >> >> +else
> >> >> >> >> >> >> +  cat > conftest.c <<EOF
> >> >> >> >> >> >> +static int var  __attribute__ ((used, retain, section ("__libc_atexit")));
> >> >> >> >> >> >> +EOF
> >> >> >> >> >> >> +libc_cv_gnu_retain=no
> >> >> >> >> >> >> +if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&5 \
> >> >> >> >> >> >> +   2>&5 ; then
> >> >> >> >> >> >> +  libc_cv_gnu_retain=yes
> >> >> >> >> >> >> +fi
> >> >> >> >> >> >> +rm -f conftest*
> >> >> >> >> >> >> +fi
> >> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gnu_retain" >&5
> >> >> >> >> >> >> +$as_echo "$libc_cv_gnu_retain" >&6; }
> >> >> >> >> >> >> +if test $libc_cv_gnu_retain = yes; then
> >> >> >> >> >> >> +  $as_echo "#define HAVE_GNU_RETAIN 1" >>confdefs.h
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +fi
> >> >> >> >> >> >> +config_vars="$config_vars
> >> >> >> >> >> >> +have-gnu-retain = $libc_cv_gnu_retain"
> >> >> >> >> >> >> +
> >> >> >> >> >> >>  # Check if gcc warns about alias for function with incompatible types.
> >> >> >> >> >> >>  { $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
> >> >> >> >> >> >>  $as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
> >> >> >> >> >> >> @@ -5871,6 +5896,40 @@ fi
> >> >> >> >> >> >>  $as_echo "$libc_linker_feature" >&6; }
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z start-stop-gc" >&5
> >> >> >> >> >> >> +$as_echo_n "checking for linker that supports -z start-stop-gc... " >&6; }
> >> >> >> >> >> >> +libc_linker_feature=no
> >> >> >> >> >> >> +if test x"$gnu_ld" = x"yes"; then
> >> >> >> >> >> >> +  libc_linker_check=`$LD -v --help 2>/dev/null | grep "\-z start-stop-gc"`
> >> >> >> >> >> >> +  if test -n "$libc_linker_check"; then
> >> >> >> >> >> >> +    cat > conftest.c <<EOF
> >> >> >> >> >> >> +int _start (void) { return 42; }
> >> >> >> >> >> >> +EOF
> >> >> >> >> >> >> +    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> >> >> >> >> >> >> +                               -Wl,-z,start-stop-gc -nostdlib -nostartfiles
> >> >> >> >> >> >> +                               -fPIC -shared -o conftest.so conftest.c
> >> >> >> >> >> >> +                               1>&5'
> >> >> >> >> >> >> +  { { eval echo "\"\$as_me\":${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_linker_feature=yes
> >> >> >> >> >> >> +    fi
> >> >> >> >> >> >> +    rm -f conftest*
> >> >> >> >> >> >> +  fi
> >> >> >> >> >> >> +fi
> >> >> >> >> >> >> +if test $libc_linker_feature = yes; then
> >> >> >> >> >> >> +  libc_cv_z_start_stop_gc=yes
> >> >> >> >> >> >> +else
> >> >> >> >> >> >> +  libc_cv_z_start_stop_gc=no
> >> >> >> >> >> >> +fi
> >> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
> >> >> >> >> >> >> +$as_echo "$libc_linker_feature" >&6; }
> >> >> >> >> >> >> +config_vars="$config_vars
> >> >> >> >> >> >> +have-z-start-stop-gc = $libc_cv_z_start_stop_gc"
> >> >> >> >> >> >> +
> >> >> >> >> >> >>  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
> >> >> >> >> >> >>  $as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
> >> >> >> >> >> >>  libc_linker_feature=no
> >> >> >> >> >> >> diff --git a/configure.ac b/configure.ac
> >> >> >> >> >> >> index fce967f2c2..cc47e56e82 100644
> >> >> >> >> >> >> --- a/configure.ac
> >> >> >> >> >> >> +++ b/configure.ac
> >> >> >> >> >> >> @@ -707,6 +707,23 @@ fi
> >> >> >> >> >> >>  rm -f conftest*])
> >> >> >> >> >> >>  AC_SUBST(libc_cv_textrel_ifunc)
> >> >> >> >> >> >>
> >> >> >> >> >> >> +# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
> >> >> >> >> >> >> +AC_CACHE_CHECK([for GNU attribute retain support],
> >> >> >> >> >> >> +              libc_cv_gnu_retain, [dnl
> >> >> >> >> >> >> +cat > conftest.c <<EOF
> >> >> >> >> >> >> +static int var  __attribute__ ((used, retain, section ("__libc_atexit")));
> >> >> >> >> >> >> +EOF
> >> >> >> >> >> >> +libc_cv_gnu_retain=no
> >> >> >> >> >> >> +if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&AS_MESSAGE_LOG_FD \
> >> >> >> >> >> >> +   2>&AS_MESSAGE_LOG_FD ; then
> >> >> >> >> >> >> +  libc_cv_gnu_retain=yes
> >> >> >> >> >> >> +fi
> >> >> >> >> >> >> +rm -f conftest*])
> >> >> >> >> >> >> +if test $libc_cv_gnu_retain = yes; then
> >> >> >> >> >> >> +  AC_DEFINE(HAVE_GNU_RETAIN)
> >> >> >> >> >> >> +fi
> >> >> >> >> >> >> +LIBC_CONFIG_VAR([have-gnu-retain], [$libc_cv_gnu_retain])
> >> >> >> >> >> >> +
> >> >> >> >> >> >>  # Check if gcc warns about alias for function with incompatible types.
> >> >> >> >> >> >>  AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
> >> >> >> >> >> >>                libc_cv_gcc_incompatible_alias, [dnl
> >> >> >> >> >> >> @@ -1317,6 +1334,10 @@ LIBC_LINKER_FEATURE([-z execstack], [-Wl,-z,execstack],
> >> >> >> >> >> >>                     [libc_cv_z_execstack=yes], [libc_cv_z_execstack=no])
> >> >> >> >> >> >>  AC_SUBST(libc_cv_z_execstack)
> >> >> >> >> >> >>
> >> >> >> >> >> >> +LIBC_LINKER_FEATURE([-z start-stop-gc], [-Wl,-z,start-stop-gc],
> >> >> >> >> >> >> +                   [libc_cv_z_start_stop_gc=yes], [libc_cv_z_start_stop_gc=no])
> >> >> >> >> >> >> +LIBC_CONFIG_VAR([have-z-start-stop-gc], [$libc_cv_z_start_stop_gc])
> >> >> >> >> >> >> +
> >> >> >> >> >> >>  LIBC_LINKER_FEATURE([--no-dynamic-linker],
> >> >> >> >> >> >>                     [-Wl,--no-dynamic-linker],
> >> >> >> >> >> >>                     [libc_cv_no_dynamic_linker=yes],
> >> >> >> >> >> >> diff --git a/include/libc-symbols.h b/include/libc-symbols.h
> >> >> >> >> >> >> index 546fc26a7b..127ea656c2 100644
> >> >> >> >> >> >> --- a/include/libc-symbols.h
> >> >> >> >> >> >> +++ b/include/libc-symbols.h
> >> >> >> >> >> >> @@ -352,6 +352,12 @@ for linking")
> >> >> >> >> >> >>
> >> >> >> >> >> >>  */
> >> >> >> >> >> >>
> >> >> >> >> >> >> +#ifdef HAVE_GNU_RETAIN
> >> >> >> >> >> >> +# define attribute_used_retain __attribute__ ((__used__, __retain__))
> >> >> >> >> >> >> +#else
> >> >> >> >> >> >> +# define attribute_used_retain __attribute__ ((__used__))
> >> >> >> >> >> >> +#endif
> >> >> >> >> >> >> +
> >> >> >> >> >> >>  /* Symbol set support macros.  */
> >> >> >> >> >> >>
> >> >> >> >> >> >>  /* Make SYMBOL, which is in the text segment, an element of SET.  */
> >> >> >> >> >> >> @@ -367,12 +373,12 @@ for linking")
> >> >> >> >> >> >>  /* When building a shared library, make the set section writable,
> >> >> >> >> >> >>     because it will need to be relocated at run time anyway.  */
> >> >> >> >> >> >>  # define _elf_set_element(set, symbol) \
> >> >> >> >> >> >> -  static const void *__elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> >> -    __attribute__ ((used, section (#set))) = &(symbol)
> >> >> >> >> >> >> +    static const void *__elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> >> +      attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
> >> >> >> >> >> >>  #else
> >> >> >> >> >> >>  # define _elf_set_element(set, symbol) \
> >> >> >> >> >> >> -  static const void *const __elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> >> -    __attribute__ ((used, section (#set))) = &(symbol)
> >> >> >> >> >> >> +    static const void *const __elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> >> +      attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
> >> >> >> >> >> >>  #endif
> >> >> >> >> >> >>
> >> >> >> >> >> >>  /* Define SET as a symbol set.  This may be required (it is in a.out) to
> >> >> >> >> >> >> diff --git a/libio/Makefile b/libio/Makefile
> >> >> >> >> >> >> index 12ce41038f..c9c232ebc2 100644
> >> >> >> >> >> >> --- a/libio/Makefile
> >> >> >> >> >> >> +++ b/libio/Makefile
> >> >> >> >> >> >> @@ -195,6 +195,20 @@ ifeq (yes,$(build-shared))
> >> >> >> >> >> >>  tests-special += $(objpfx)tst-fopenloc-cmp.out $(objpfx)tst-fopenloc-mem.out \
> >> >> >> >> >> >>                  $(objpfx)tst-bz24228-mem.out
> >> >> >> >> >> >>  endif
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +tests += tst-cleanup-default
> >> >> >> >> >> >> +tests-static += tst-cleanup-default
> >> >> >> >> >> >> +tests-special += $(objpfx)tst-cleanup-default-cmp.out
> >> >> >> >> >> >
> >> >> >> >> >> >Please make 2 tests,  tst-cleanup-default and tst-cleanup-default-static.
> >> >> >> >> >>
> >> >> >> >> >> Added.
> >> >> >> >> >>
> >> >> >> >> >> >> +LDFLAGS-tst-cleanup-default = -Wl,--gc-sections
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +ifeq ($(have-gnu-retain)$(have-z-start-stop-gc),yesyes)
> >> >> >> >> >> >> +tests += tst-cleanup-start-stop-gc tst-cleanup-nostart-stop-gc
> >> >> >> >> >> >> +tests-static += tst-cleanup-start-stop-gc tst-cleanup-nostart-stop-gc
> >> >> >> >> >> >> +tests-special += $(objpfx)tst-cleanup-start-stop-gc-cmp.out \
> >> >> >> >> >> >> +               $(objpfx)tst-cleanup-nostart-stop-gc-cmp.out
> >> >> >> >> >> >
> >> >> >> >> >> >Same here.
> >> >> >> >> >>
> >> >> >> >> >> Added.
> >> >> >> >> >>
> >> >> >> >> >> >> +LDFLAGS-tst-cleanup-start-stop-gc = -Wl,--gc-sections,-z,start-stop-gc
> >> >> >> >> >> >> +LDFLAGS-tst-cleanup-nostart-stop-gc = -Wl,--gc-sections,-z,nostart-stop-gc
> >> >> >> >> >> >> +endif
> >> >> >> >> >> >>  endif
> >> >> >> >> >> >>
> >> >> >> >> >> >>  include ../Rules
> >> >> >> >> >> >> @@ -224,6 +238,24 @@ $(objpfx)tst_wprintf2.out: $(gen-locales)
> >> >> >> >> >> >>  $(objpfx)tst-wfile-sync.out: $(gen-locales)
> >> >> >> >> >> >>  endif
> >> >> >> >> >> >>
> >> >> >> >> >> >> +$(objpfx)tst-cleanup-default-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-default.out
> >> >> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> >> >> +$(objpfx)tst-cleanup-default.o: tst-cleanup.c
> >> >> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-start-stop-gc.out
> >> >> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc.o: tst-cleanup.c
> >> >> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +$(objpfx)tst-cleanup-nostart-stop-gc-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-nostart-stop-gc.out
> >> >> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> >> >> +$(objpfx)tst-cleanup-nostart-stop-gc.o: tst-cleanup.c
> >> >> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> >> >>
> >> >> >> >> >> >>  $(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen
> >> >> >> >> >> >>         $(SHELL) $< $(common-objpfx) '$(test-program-prefix)'   \
> >> >> >> >> >> >>         $(common-objpfx)libio/; \
> >> >> >> >> >> >> diff --git a/libio/tst-cleanup.c b/libio/tst-cleanup.c
> >> >> >> >> >> >> new file mode 100644
> >> >> >> >> >> >> index 0000000000..7f0a34a91e
> >> >> >> >> >> >> --- /dev/null
> >> >> >> >> >> >> +++ b/libio/tst-cleanup.c
> >> >> >> >> >> >> @@ -0,0 +1,33 @@
> >> >> >> >> >> >
> >> >> >> >> >> >Please add a comment saying that test --gc-sections.
> >> >> >> >> >>
> >> >> >> >> >> OK, added.
> >> >> >> >> >>
> >> >> >> >> >> >> +/* Copyright (C) 2021 Free Software Foundation, Inc.
> >> >> >> >> >> >> +   This file is part of the GNU C Library.
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +   The GNU C Library is free software; you can redistribute it and/or
> >> >> >> >> >> >> +   modify it under the terms of the GNU Lesser General Public
> >> >> >> >> >> >> +   License as published by the Free Software Foundation; either
> >> >> >> >> >> >> +   version 2.1 of the License, or (at your option) any later version.
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +   The GNU C Library is distributed in the hope that it will be useful,
> >> >> >> >> >> >> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> >> >> >> >> >> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> >> >> >> >> >> >> +   Lesser General Public License for more details.
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +   You should have received a copy of the GNU Lesser General Public
> >> >> >> >> >> >> +   License along with the GNU C Library; if not, see
> >> >> >> >> >> >> +   <https://www.gnu.org/licenses/>.  */
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +/* Test that stdout is flushed after atexit callbacks were run.  */
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +#include <stdio.h>
> >> >> >> >> >> >> +#include <stdlib.h>
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +void
> >> >> >> >> >> >> +hook (void)
> >> >> >> >> >> >> +{
> >> >> >> >> >> >> +  puts ("hello");
> >> >> >> >> >> >> +}
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +int
> >> >> >> >> >> >> +main (void)
> >> >> >> >> >> >> +{
> >> >> >> >> >> >> +  atexit (hook);
> >> >> >> >> >> >> +}
> >> >> >> >> >> >> diff --git a/libio/tst-cleanup.exp b/libio/tst-cleanup.exp
> >> >> >> >> >> >> new file mode 100644
> >> >> >> >> >> >> index 0000000000..ce01362503
> >> >> >> >> >> >> --- /dev/null
> >> >> >> >> >> >> +++ b/libio/tst-cleanup.exp
> >> >> >> >> >> >> @@ -0,0 +1 @@
> >> >> >> >> >> >> +hello
> >> >> >> >> >> >> --
> >> >> >> >> >> >> 2.31.0.291.g576ba9dcdaf-goog
> >> >> >> >> >> >>
> >> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >> diff --git a/config.h.in b/config.h.in
> >> >> >> >> >> index ca1547ae67..96a08c7757 100644
> >> >> >> >> >> --- a/config.h.in
> >> >> >> >> >> +++ b/config.h.in
> >> >> >> >> >> @@ -187,6 +187,9 @@
> >> >> >> >> >>   /* Define if gcc supports attribute ifunc.  */
> >> >> >> >> >>   #undef HAVE_GCC_IFUNC
> >> >> >> >> >>
> >> >> >> >> >> +/* Define if CC supports attribute retain.  */
> >> >> >> >> >> +#undef HAVE_GNU_RETAIN
> >> >> >> >> >> +
> >> >> >> >> >>   /* Define if the linker defines __ehdr_start.  */
> >> >> >> >> >>   #undef HAVE_EHDR_START
> >> >> >> >> >>
> >> >> >> >> >> diff --git a/configure b/configure
> >> >> >> >> >> index fcf43bf7de..e64b7f8efe 100755
> >> >> >> >> >> --- a/configure
> >> >> >> >> >> +++ b/configure
> >> >> >> >> >> @@ -4105,6 +4105,31 @@ fi
> >> >> >> >> >>   $as_echo "$libc_cv_textrel_ifunc" >&6; }
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> +# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for GNU attribute retain support" >&5
> >> >> >> >> >> +$as_echo_n "checking for GNU attribute retain support... " >&6; }
> >> >> >> >> >> +if ${libc_cv_gnu_retain+:} false; then :
> >> >> >> >> >> +  $as_echo_n "(cached) " >&6
> >> >> >> >> >> +else
> >> >> >> >> >> +  cat > conftest.c <<EOF
> >> >> >> >> >> +static int var  __attribute__ ((used, retain, section ("__libc_atexit")));
> >> >> >> >> >> +EOF
> >> >> >> >> >> +libc_cv_gnu_retain=no
> >> >> >> >> >> +if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&5 \
> >> >> >> >> >> +   2>&5 ; then
> >> >> >> >> >> +  libc_cv_gnu_retain=yes
> >> >> >> >> >> +fi
> >> >> >> >> >> +rm -f conftest*
> >> >> >> >> >> +fi
> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gnu_retain" >&5
> >> >> >> >> >> +$as_echo "$libc_cv_gnu_retain" >&6; }
> >> >> >> >> >> +if test $libc_cv_gnu_retain = yes; then
> >> >> >> >> >> +  $as_echo "#define HAVE_GNU_RETAIN 1" >>confdefs.h
> >> >> >> >> >> +
> >> >> >> >> >> +fi
> >> >> >> >> >> +config_vars="$config_vars
> >> >> >> >> >> +have-gnu-retain = $libc_cv_gnu_retain"
> >> >> >> >> >> +
> >> >> >> >> >>   # Check if gcc warns about alias for function with incompatible types.
> >> >> >> >> >>   { $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
> >> >> >> >> >>   $as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
> >> >> >> >> >> @@ -5871,6 +5896,40 @@ fi
> >> >> >> >> >>   $as_echo "$libc_linker_feature" >&6; }
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z start-stop-gc" >&5
> >> >> >> >> >> +$as_echo_n "checking for linker that supports -z start-stop-gc... " >&6; }
> >> >> >> >> >> +libc_linker_feature=no
> >> >> >> >> >> +if test x"$gnu_ld" = x"yes"; then
> >> >> >> >> >> +  libc_linker_check=`$LD -v --help 2>/dev/null | grep "\-z start-stop-gc"`
> >> >> >> >> >> +  if test -n "$libc_linker_check"; then
> >> >> >> >> >> +    cat > conftest.c <<EOF
> >> >> >> >> >> +int _start (void) { return 42; }
> >> >> >> >> >> +EOF
> >> >> >> >> >> +    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> >> >> >> >> >> +                               -Wl,-z,start-stop-gc -nostdlib -nostartfiles
> >> >> >> >> >> +                               -fPIC -shared -o conftest.so conftest.c
> >> >> >> >> >> +                               1>&5'
> >> >> >> >> >> +  { { eval echo "\"\$as_me\":${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_linker_feature=yes
> >> >> >> >> >> +    fi
> >> >> >> >> >> +    rm -f conftest*
> >> >> >> >> >> +  fi
> >> >> >> >> >> +fi
> >> >> >> >> >> +if test $libc_linker_feature = yes; then
> >> >> >> >> >> +  libc_cv_z_start_stop_gc=yes
> >> >> >> >> >> +else
> >> >> >> >> >> +  libc_cv_z_start_stop_gc=no
> >> >> >> >> >> +fi
> >> >> >> >> >> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
> >> >> >> >> >> +$as_echo "$libc_linker_feature" >&6; }
> >> >> >> >> >> +config_vars="$config_vars
> >> >> >> >> >> +have-z-start-stop-gc = $libc_cv_z_start_stop_gc"
> >> >> >> >> >> +
> >> >> >> >> >>   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
> >> >> >> >> >>   $as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
> >> >> >> >> >>   libc_linker_feature=no
> >> >> >> >> >> diff --git a/configure.ac b/configure.ac
> >> >> >> >> >> index fce967f2c2..cc47e56e82 100644
> >> >> >> >> >> --- a/configure.ac
> >> >> >> >> >> +++ b/configure.ac
> >> >> >> >> >> @@ -707,6 +707,23 @@ fi
> >> >> >> >> >>   rm -f conftest*])
> >> >> >> >> >>   AC_SUBST(libc_cv_textrel_ifunc)
> >> >> >> >> >>
> >> >> >> >> >> +# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
> >> >> >> >> >> +AC_CACHE_CHECK([for GNU attribute retain support],
> >> >> >> >> >> +              libc_cv_gnu_retain, [dnl
> >> >> >> >> >> +cat > conftest.c <<EOF
> >> >> >> >> >> +static int var  __attribute__ ((used, retain, section ("__libc_atexit")));
> >> >> >> >> >> +EOF
> >> >> >> >> >> +libc_cv_gnu_retain=no
> >> >> >> >> >> +if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&AS_MESSAGE_LOG_FD \
> >> >> >> >> >> +   2>&AS_MESSAGE_LOG_FD ; then
> >> >> >> >> >> +  libc_cv_gnu_retain=yes
> >> >> >> >> >> +fi
> >> >> >> >> >> +rm -f conftest*])
> >> >> >> >> >> +if test $libc_cv_gnu_retain = yes; then
> >> >> >> >> >> +  AC_DEFINE(HAVE_GNU_RETAIN)
> >> >> >> >> >> +fi
> >> >> >> >> >> +LIBC_CONFIG_VAR([have-gnu-retain], [$libc_cv_gnu_retain])
> >> >> >> >> >> +
> >> >> >> >> >>   # Check if gcc warns about alias for function with incompatible types.
> >> >> >> >> >>   AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
> >> >> >> >> >>                libc_cv_gcc_incompatible_alias, [dnl
> >> >> >> >> >> @@ -1317,6 +1334,10 @@ LIBC_LINKER_FEATURE([-z execstack], [-Wl,-z,execstack],
> >> >> >> >> >>                     [libc_cv_z_execstack=yes], [libc_cv_z_execstack=no])
> >> >> >> >> >>   AC_SUBST(libc_cv_z_execstack)
> >> >> >> >> >>
> >> >> >> >> >> +LIBC_LINKER_FEATURE([-z start-stop-gc], [-Wl,-z,start-stop-gc],
> >> >> >> >> >> +                   [libc_cv_z_start_stop_gc=yes], [libc_cv_z_start_stop_gc=no])
> >> >> >> >> >> +LIBC_CONFIG_VAR([have-z-start-stop-gc], [$libc_cv_z_start_stop_gc])
> >> >> >> >> >> +
> >> >> >> >> >>   LIBC_LINKER_FEATURE([--no-dynamic-linker],
> >> >> >> >> >>                     [-Wl,--no-dynamic-linker],
> >> >> >> >> >>                     [libc_cv_no_dynamic_linker=yes],
> >> >> >> >> >> diff --git a/include/libc-symbols.h b/include/libc-symbols.h
> >> >> >> >> >> index 546fc26a7b..127ea656c2 100644
> >> >> >> >> >> --- a/include/libc-symbols.h
> >> >> >> >> >> +++ b/include/libc-symbols.h
> >> >> >> >> >> @@ -352,6 +352,12 @@ for linking")
> >> >> >> >> >>
> >> >> >> >> >>   */
> >> >> >> >> >>
> >> >> >> >> >> +#ifdef HAVE_GNU_RETAIN
> >> >> >> >> >> +# define attribute_used_retain __attribute__ ((__used__, __retain__))
> >> >> >> >> >> +#else
> >> >> >> >> >> +# define attribute_used_retain __attribute__ ((__used__))
> >> >> >> >> >> +#endif
> >> >> >> >> >> +
> >> >> >> >> >>   /* Symbol set support macros.  */
> >> >> >> >> >>
> >> >> >> >> >>   /* Make SYMBOL, which is in the text segment, an element of SET.  */
> >> >> >> >> >> @@ -367,12 +373,12 @@ for linking")
> >> >> >> >> >>   /* When building a shared library, make the set section writable,
> >> >> >> >> >>      because it will need to be relocated at run time anyway.  */
> >> >> >> >> >>   # define _elf_set_element(set, symbol) \
> >> >> >> >> >> -  static const void *__elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> -    __attribute__ ((used, section (#set))) = &(symbol)
> >> >> >> >> >> +    static const void *__elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> +      attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
> >> >> >> >> >>   #else
> >> >> >> >> >>   # define _elf_set_element(set, symbol) \
> >> >> >> >> >> -  static const void *const __elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> -    __attribute__ ((used, section (#set))) = &(symbol)
> >> >> >> >> >> +    static const void *const __elf_set_##set##_element_##symbol##__ \
> >> >> >> >> >> +      attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
> >> >> >> >> >>   #endif
> >> >> >> >> >>
> >> >> >> >> >>   /* Define SET as a symbol set.  This may be required (it is in a.out) to
> >> >> >> >> >> diff --git a/libio/Makefile b/libio/Makefile
> >> >> >> >> >> index 12ce41038f..ad0d53bb49 100644
> >> >> >> >> >> --- a/libio/Makefile
> >> >> >> >> >> +++ b/libio/Makefile
> >> >> >> >> >> @@ -195,6 +195,26 @@ ifeq (yes,$(build-shared))
> >> >> >> >> >>   tests-special += $(objpfx)tst-fopenloc-cmp.out $(objpfx)tst-fopenloc-mem.out \
> >> >> >> >> >>                  $(objpfx)tst-bz24228-mem.out
> >> >> >> >> >>   endif
> >> >> >> >> >> +
> >> >> >> >> >> +tests += tst-cleanup-default tst-cleanup-default-static
> >> >> >> >> >> +tests-static += tst-cleanup-default-static
> >> >> >> >> >> +tests-special += $(objpfx)tst-cleanup-default-cmp.out $(objpfx)tst-cleanup-default-static-cmp.out
> >> >> >> >> >> +LDFLAGS-tst-cleanup-default = -Wl,--gc-sections
> >> >> >> >> >> +LDFLAGS-tst-cleanup-default-static = -Wl,--gc-sections
> >> >> >> >> >> +
> >> >> >> >> >> +ifeq ($(have-gnu-retain)$(have-z-start-stop-gc),yesyes)
> >> >> >> >> >> +tests += tst-cleanup-start-stop-gc tst-cleanup-start-stop-gc-static \
> >> >> >> >> >> +               tst-cleanup-nostart-stop-gc tst-cleanup-nostart-stop-gc-static
> >> >> >> >> >> +tests-static += tst-cleanup-start-stop-gc-static tst-cleanup-nostart-stop-gc-static
> >> >> >> >> >> +tests-special += $(objpfx)tst-cleanup-start-stop-gc-cmp.out \
> >> >> >> >> >> +               $(objpfx)tst-cleanup-start-stop-gc-static-cmp.out \
> >> >> >> >> >> +               $(objpfx)tst-cleanup-nostart-stop-gc-cmp.out \
> >> >> >> >> >> +               $(objpfx)tst-cleanup-nostart-stop-gc-static-cmp.out
> >> >> >> >> >> +LDFLAGS-tst-cleanup-start-stop-gc := -Wl,--gc-sections,-z,start-stop-gc
> >> >> >> >> >> +LDFLAGS-tst-cleanup-start-stop-gc-static := -Wl,--gc-sections,-z,start-stop-gc
> >> >> >> >> >> +LDFLAGS-tst-cleanup-nostart-stop-gc := -Wl,--gc-sections,-z,nostart-stop-gc
> >> >> >> >> >> +LDFLAGS-tst-cleanup-nostart-stop-gc-static := -Wl,--gc-sections,-z,nostart-stop-gc
> >> >> >> >> >> +endif
> >> >> >> >> >>   endif
> >> >> >> >> >>
> >> >> >> >> >>   include ../Rules
> >> >> >> >> >> @@ -224,6 +244,39 @@ $(objpfx)tst_wprintf2.out: $(gen-locales)
> >> >> >> >> >>   $(objpfx)tst-wfile-sync.out: $(gen-locales)
> >> >> >> >> >>   endif
> >> >> >> >> >>
> >> >> >> >> >> +$(objpfx)tst-cleanup-default-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-default.out
> >> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> >> +$(objpfx)tst-cleanup-default.o: tst-cleanup.c
> >> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> >> +$(objpfx)tst-cleanup-default-static-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-default-static.out
> >> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> >> +$(objpfx)tst-cleanup-default-static.o: tst-cleanup.c
> >> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> >> +
> >> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-start-stop-gc.out
> >> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc.o: tst-cleanup.c
> >> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc-static-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-start-stop-gc-static.out
> >> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc-static.o: tst-cleanup.c
> >> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> >
> >> >> >> >> >Please add a separate .c file for each test to get the correct dependency.
> >> >> >> >>
> >> >> >> >> Changed this block to:
> >> >> >> >>
> >> >> >> >> @@ -224,6 +244,39 @@ $(objpfx)tst_wprintf2.out: $(gen-locales)
> >> >> >> >>   $(objpfx)tst-wfile-sync.out: $(gen-locales)
> >> >> >> >>   endif
> >> >> >> >>
> >> >> >> >> +$(objpfx)tst-cleanup-default-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-default.out
> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> +$(objpfx)tst-cleanup-default.c: tst-cleanup.c
> >> >> >> >> +       cp $< $@
> >> >> >> >> +$(objpfx)tst-cleanup-default-static-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-default-static.out
> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> +$(objpfx)tst-cleanup-default-static.c: tst-cleanup.c
> >> >> >> >> +       cp $< $@
> >> >> >> >> +
> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-start-stop-gc.out
> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc.o: tst-cleanup.c
> >> >> >> >> +       $(compile.c) -o $@
> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc-static-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-start-stop-gc-static.out
> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> +$(objpfx)tst-cleanup-start-stop-gc-static.c: tst-cleanup.c
> >> >> >> >> +       cp $< $@
> >> >> >> >> +
> >> >> >> >> +$(objpfx)tst-cleanup-nostart-stop-gc-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-nostart-stop-gc.out
> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> +$(objpfx)tst-cleanup-nostart-stop-gc.c: tst-cleanup.c
> >> >> >> >> +       cp $< $@
> >> >> >> >> +$(objpfx)tst-cleanup-nostart-stop-gc-static-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-nostart-stop-gc-static.out
> >> >> >> >> +       cmp $^ > $@; \
> >> >> >> >> +       $(evaluate-test)
> >> >> >> >> +$(objpfx)tst-cleanup-nostart-stop-gc-static.c: tst-cleanup.c
> >> >> >> >> +       cp $< $@
> >> >> >> >> +
> >> >> >> >>   $(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen
> >> >> >> >>         $(SHELL) $< $(common-objpfx) '$(test-program-prefix)'   \
> >> >> >> >>         $(common-objpfx)libio/; \
> >> >> >> >>
> >> >> >> >
> >> >> >> >"make clean" doesn't remove the generated files. The standard way in glibc
> >> >> >> >is to add a *-static.c source.
> >> >> >>
> >> >> >> I'll use .INTERMEDIATE and $(eval $(call ..))
> >> >> >>
> >> >> >> diff --git a/libio/Makefile b/libio/Makefile
> >> >> >> index 12ce41038f..a9b44f04df 100644
> >> >> >> --- a/libio/Makefile
> >> >> >> +++ b/libio/Makefile
> >> >> >> @@ -195,6 +195,26 @@ ifeq (yes,$(build-shared))
> >> >> >>   tests-special += $(objpfx)tst-fopenloc-cmp.out $(objpfx)tst-fopenloc-mem.out \
> >> >> >>                  $(objpfx)tst-bz24228-mem.out
> >> >> >>   endif
> >> >> >> +
> >> >> >> +tests += tst-cleanup-default tst-cleanup-default-static
> >> >> >> +tests-static += tst-cleanup-default-static
> >> >> >> +tests-special += $(objpfx)tst-cleanup-default-cmp.out $(objpfx)tst-cleanup-default-static-cmp.out
> >> >> >> +LDFLAGS-tst-cleanup-default = -Wl,--gc-sections
> >> >> >> +LDFLAGS-tst-cleanup-default-static = -Wl,--gc-sections
> >> >> >> +
> >> >> >> +ifeq ($(have-gnu-retain)$(have-z-start-stop-gc),yesyes)
> >> >> >> +tests += tst-cleanup-start-stop-gc tst-cleanup-start-stop-gc-static \
> >> >> >> +               tst-cleanup-nostart-stop-gc tst-cleanup-nostart-stop-gc-static
> >> >> >> +tests-static += tst-cleanup-start-stop-gc-static tst-cleanup-nostart-stop-gc-static
> >> >> >> +tests-special += $(objpfx)tst-cleanup-start-stop-gc-cmp.out \
> >> >> >> +               $(objpfx)tst-cleanup-start-stop-gc-static-cmp.out \
> >> >> >> +               $(objpfx)tst-cleanup-nostart-stop-gc-cmp.out \
> >> >> >> +               $(objpfx)tst-cleanup-nostart-stop-gc-static-cmp.out
> >> >> >> +LDFLAGS-tst-cleanup-start-stop-gc := -Wl,--gc-sections,-z,start-stop-gc
> >> >> >> +LDFLAGS-tst-cleanup-start-stop-gc-static := -Wl,--gc-sections,-z,start-stop-gc
> >> >> >> +LDFLAGS-tst-cleanup-nostart-stop-gc := -Wl,--gc-sections,-z,nostart-stop-gc
> >> >> >> +LDFLAGS-tst-cleanup-nostart-stop-gc-static := -Wl,--gc-sections,-z,nostart-stop-gc
> >> >> >> +endif
> >> >> >>   endif
> >> >> >>
> >> >> >>   include ../Rules
> >> >> >> @@ -224,6 +244,17 @@ $(objpfx)tst_wprintf2.out: $(gen-locales)
> >> >> >>   $(objpfx)tst-wfile-sync.out: $(gen-locales)
> >> >> >>   endif
> >> >> >>
> >> >> >> +define gen-tst-cleanup
> >> >> >> +$(objpfx)tst-cleanup-$1-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-$1.out
> >> >> >> +       cmp $$^ > $$@; $$(evaluate-test)
> >> >> >> +$(objpfx)tst-cleanup-$1.c: tst-cleanup.c
> >> >> >> +       cp $$< $$@
> >> >> >> +.INTERMEDIATE: $(objpfx)tst-cleanup-$1.c
> >> >> >> +endef
> >> >> >> +
> >> >> >> +$(foreach t, default default-static start-stop-gc start-stop-gc-static nostart-stop-gc nostart-stop-gc-static, \
> >> >> >> +  $(eval $(call gen-tst-cleanup,$(t))))
> >> >> >> +
> >> >> >>   $(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen
> >> >> >>         $(SHELL) $< $(common-objpfx) '$(test-program-prefix)'   \
> >> >> >>         $(common-objpfx)libio/; \
> >> >> >
> >> >> >There are 2 issues with static tests:
> >> >> >
> >> >> >1. A separate static source is needed.
> >> >>
> >> >> .INTERMEDIATE perfectly solves the lingering copied source issue.
> >> >> I don't see lingering libio/tst-cleanup-*.c
> >> >
> >> >I was referring to
> >> >
> >> >elf/tst-array1-static.c
> >> >elf/tst-array5-static.c
> >> >elf/tst-dl-iter-static.c
> >> >elf/tst-dst-static.c
> >> >elf/tst-leaks1-static.c
> >> >elf/tst-libc_dlvsym-static.c
> >> >elf/tst-linkall-static.c
> >> >elf/tst-ptrguard1-static.c
> >> >elf/tst-single_threaded-pthread-static.c
> >> >elf/tst-single_threaded-static.c
> >> >elf/tst-stackguard1-static.c
> >> >elf/tst-tls1-static.c
> >> >elf/tst-tls2-static.c
> >> >elf/tst-tls9-static.c
> >> >elf/tst-tlsalign-extern-static.c
> >> >elf/tst-tlsalign-static.c
> >> >gmon/tst-gmon-static.c
> >> >gmon/tst-profile-static.c
> >> >localedata/bug-setlocale1-static.c
> >> >localedata/tst-langinfo-newlocale-static.c
> >> >localedata/tst-langinfo-setlocale-static.c
> >> >localedata/tst-langinfo-static.c
> >> >malloc/tst-malloc-usable-static.c
> >> >math/test-fpucw-ieee-static.c
> >> >math/test-fpucw-static.c
> >> >math/test-signgam-uchar-init-static.c
> >> >math/test-signgam-uchar-static.c
> >> >math/test-signgam-uint-init-static.c
> >> >math/test-signgam-uint-static.c
> >> >math/test-signgam-ullong-init-static.c
> >> >math/test-signgam-ullong-static.c
> >> >nptl/tst-mutex8-static.c
> >> >nptl/tst-mutexpi8-static.c
> >> >nptl/tst-sem11-static.c
> >> >nptl/tst-sem12-static.c
> >> >nptl/tst-setuid1-static.c
> >> >nptl/tst-stackguard1-static.c
> >> >nss/tst-nss-static.c
> >> >posix/tst-exec-static.c
> >> >posix/tst-spawn-static.c
> >> >setjmp/tst-setjmp-static.c
> >> >
> >> >> >2. We need to add the static test to both tests and tests-static.
> >> >>
> >> >> tests-static suffices. I have checked some tests-static usage in other
> >> >> directories.
> >> >
> >> >There are
> >> >
> >> >tests           := tst-setjmp jmpbug bug269-setjmp tst-setjmp-fp \
> >> >                   tst-sigsetjmp tst-setjmp-static
> >> >tests-static    := tst-setjmp-static
> >> >
> >> >They should be replaced by something like
> >> >
> >> >tests           := tst-setjmp jmpbug bug269-setjmp tst-setjmp-fp \
> >> >                   tst-sigsetjmp
> >> >tests-static-add := tst-setjmp-static
> >>
> >> Re-checking, the tst-cleanup* targets are in tests-special so `make tests` will build them.
> >> If a tests-static target is not in tests-internal/tests-special, looks like it needs to be in tests.
> >>
> >> As is, I think my usage is correct.
> >>
> >
> >The current glibc convention is to use
> >
> >[hjl@gnu-cfl-2 x86-glibc]$ cat elf/tst-tls9-static.c
> >#include "tst-tls9.c"
> >[hjl@gnu-cfl-2 x86-glibc]$
> >
> >to test both dynamic and static libc.  If we want to use a single
> >source, we should create
> >a framework to cover all such tests.
>
> OK. Dropped cp $< $@ and .INTERMEDIATE
>
>
>  From e937ae26a4a9a8ff6b1198f347f0b141a9285305 Mon Sep 17 00:00:00 2001
> From: Fangrui Song <maskray@google.com>
> Date: Tue, 6 Apr 2021 14:45:01 -0700
> Subject: [PATCH] Set the retain attribute on _elf_set_element if CC supports
>   [BZ #27492]
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> So that text_set_element/data_set_element/bss_set_element defined
> variables will be retained by the linker.
>
> Note: 'used' and 'retain' are orthogonal: 'used' makes sure the variable
> will not be optimized out; 'retain' prevents section garbage collection
> if the linker support SHF_GNU_RETAIN.
>
> GNU ld 2.37 and LLD 13 will support -z start-stop-gc which allow C
> identifier name sections to be GCed even if there are live
> __start_/__stop_ references.
>
> Without the change, there are some static linking problems, e.g.
> _IO_cleanup (libio/genops.c) may be discarded by ld --gc-sections, so
> stdout is not flushed on exit.
>
> Note: GCC may warning ‘retain’ attribute ignored while __has_attribute(retain) is 1
> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99587).
> ---
>   config.h.in                                |  3 ++
>   configure                                  | 59 ++++++++++++++++++++++
>   configure.ac                               | 21 ++++++++
>   include/libc-symbols.h                     | 14 +++--
>   libio/Makefile                             | 28 ++++++++++
>   libio/tst-cleanup-default-static.c         |  1 +
>   libio/tst-cleanup-default.c                |  1 +
>   libio/tst-cleanup-nostart-stop-gc-static.c |  1 +
>   libio/tst-cleanup-nostart-stop-gc.c        |  1 +
>   libio/tst-cleanup-start-stop-gc-static.c   |  1 +
>   libio/tst-cleanup-start-stop-gc.c          |  1 +
>   libio/tst-cleanup.c                        | 34 +++++++++++++
>   libio/tst-cleanup.exp                      |  1 +
>   13 files changed, 162 insertions(+), 4 deletions(-)
>   create mode 100644 libio/tst-cleanup-default-static.c
>   create mode 100644 libio/tst-cleanup-default.c
>   create mode 100644 libio/tst-cleanup-nostart-stop-gc-static.c
>   create mode 100644 libio/tst-cleanup-nostart-stop-gc.c
>   create mode 100644 libio/tst-cleanup-start-stop-gc-static.c
>   create mode 100644 libio/tst-cleanup-start-stop-gc.c
>   create mode 100644 libio/tst-cleanup.c
>   create mode 100644 libio/tst-cleanup.exp
>
> diff --git a/config.h.in b/config.h.in
> index ca1547ae67..96a08c7757 100644
> --- a/config.h.in
> +++ b/config.h.in
> @@ -187,6 +187,9 @@
>   /* Define if gcc supports attribute ifunc.  */
>   #undef HAVE_GCC_IFUNC
>
> +/* Define if CC supports attribute retain.  */
> +#undef HAVE_GNU_RETAIN
> +
>   /* Define if the linker defines __ehdr_start.  */
>   #undef HAVE_EHDR_START
>
> diff --git a/configure b/configure
> index fcf43bf7de..e64b7f8efe 100755
> --- a/configure
> +++ b/configure
> @@ -4105,6 +4105,31 @@ fi
>   $as_echo "$libc_cv_textrel_ifunc" >&6; }
>
>
> +# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for GNU attribute retain support" >&5
> +$as_echo_n "checking for GNU attribute retain support... " >&6; }
> +if ${libc_cv_gnu_retain+:} false; then :
> +  $as_echo_n "(cached) " >&6
> +else
> +  cat > conftest.c <<EOF
> +static int var  __attribute__ ((used, retain, section ("__libc_atexit")));
> +EOF
> +libc_cv_gnu_retain=no
> +if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&5 \
> +   2>&5 ; then
> +  libc_cv_gnu_retain=yes
> +fi
> +rm -f conftest*
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gnu_retain" >&5
> +$as_echo "$libc_cv_gnu_retain" >&6; }
> +if test $libc_cv_gnu_retain = yes; then
> +  $as_echo "#define HAVE_GNU_RETAIN 1" >>confdefs.h
> +
> +fi
> +config_vars="$config_vars
> +have-gnu-retain = $libc_cv_gnu_retain"
> +
>   # Check if gcc warns about alias for function with incompatible types.
>   { $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
>   $as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
> @@ -5871,6 +5896,40 @@ fi
>   $as_echo "$libc_linker_feature" >&6; }
>
>
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z start-stop-gc" >&5
> +$as_echo_n "checking for linker that supports -z start-stop-gc... " >&6; }
> +libc_linker_feature=no
> +if test x"$gnu_ld" = x"yes"; then
> +  libc_linker_check=`$LD -v --help 2>/dev/null | grep "\-z start-stop-gc"`
> +  if test -n "$libc_linker_check"; then
> +    cat > conftest.c <<EOF
> +int _start (void) { return 42; }
> +EOF
> +    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> +                               -Wl,-z,start-stop-gc -nostdlib -nostartfiles
> +                               -fPIC -shared -o conftest.so conftest.c
> +                               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_linker_feature=yes
> +    fi
> +    rm -f conftest*
> +  fi
> +fi
> +if test $libc_linker_feature = yes; then
> +  libc_cv_z_start_stop_gc=yes
> +else
> +  libc_cv_z_start_stop_gc=no
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
> +$as_echo "$libc_linker_feature" >&6; }
> +config_vars="$config_vars
> +have-z-start-stop-gc = $libc_cv_z_start_stop_gc"
> +
>   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
>   $as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
>   libc_linker_feature=no
> diff --git a/configure.ac b/configure.ac
> index fce967f2c2..cc47e56e82 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -707,6 +707,23 @@ fi
>   rm -f conftest*])
>   AC_SUBST(libc_cv_textrel_ifunc)
>
> +# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
> +AC_CACHE_CHECK([for GNU attribute retain support],
> +              libc_cv_gnu_retain, [dnl
> +cat > conftest.c <<EOF
> +static int var  __attribute__ ((used, retain, section ("__libc_atexit")));
> +EOF
> +libc_cv_gnu_retain=no
> +if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&AS_MESSAGE_LOG_FD \
> +   2>&AS_MESSAGE_LOG_FD ; then
> +  libc_cv_gnu_retain=yes
> +fi
> +rm -f conftest*])
> +if test $libc_cv_gnu_retain = yes; then
> +  AC_DEFINE(HAVE_GNU_RETAIN)
> +fi
> +LIBC_CONFIG_VAR([have-gnu-retain], [$libc_cv_gnu_retain])
> +
>   # Check if gcc warns about alias for function with incompatible types.
>   AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
>                libc_cv_gcc_incompatible_alias, [dnl
> @@ -1317,6 +1334,10 @@ LIBC_LINKER_FEATURE([-z execstack], [-Wl,-z,execstack],
>                     [libc_cv_z_execstack=yes], [libc_cv_z_execstack=no])
>   AC_SUBST(libc_cv_z_execstack)
>
> +LIBC_LINKER_FEATURE([-z start-stop-gc], [-Wl,-z,start-stop-gc],
> +                   [libc_cv_z_start_stop_gc=yes], [libc_cv_z_start_stop_gc=no])
> +LIBC_CONFIG_VAR([have-z-start-stop-gc], [$libc_cv_z_start_stop_gc])
> +
>   LIBC_LINKER_FEATURE([--no-dynamic-linker],
>                     [-Wl,--no-dynamic-linker],
>                     [libc_cv_no_dynamic_linker=yes],
> diff --git a/include/libc-symbols.h b/include/libc-symbols.h
> index 546fc26a7b..127ea656c2 100644
> --- a/include/libc-symbols.h
> +++ b/include/libc-symbols.h
> @@ -352,6 +352,12 @@ for linking")
>
>   */
>
> +#ifdef HAVE_GNU_RETAIN
> +# define attribute_used_retain __attribute__ ((__used__, __retain__))
> +#else
> +# define attribute_used_retain __attribute__ ((__used__))
> +#endif
> +
>   /* Symbol set support macros.  */
>
>   /* Make SYMBOL, which is in the text segment, an element of SET.  */
> @@ -367,12 +373,12 @@ for linking")
>   /* When building a shared library, make the set section writable,
>      because it will need to be relocated at run time anyway.  */
>   # define _elf_set_element(set, symbol) \
> -  static const void *__elf_set_##set##_element_##symbol##__ \
> -    __attribute__ ((used, section (#set))) = &(symbol)
> +    static const void *__elf_set_##set##_element_##symbol##__ \
> +      attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
>   #else
>   # define _elf_set_element(set, symbol) \
> -  static const void *const __elf_set_##set##_element_##symbol##__ \
> -    __attribute__ ((used, section (#set))) = &(symbol)
> +    static const void *const __elf_set_##set##_element_##symbol##__ \
> +      attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
>   #endif
>
>   /* Define SET as a symbol set.  This may be required (it is in a.out) to
> diff --git a/libio/Makefile b/libio/Makefile
> index 12ce41038f..ed0ce4ee81 100644
> --- a/libio/Makefile
> +++ b/libio/Makefile
> @@ -195,6 +195,26 @@ ifeq (yes,$(build-shared))
>   tests-special += $(objpfx)tst-fopenloc-cmp.out $(objpfx)tst-fopenloc-mem.out \
>                  $(objpfx)tst-bz24228-mem.out
>   endif
> +
> +tests += tst-cleanup-default tst-cleanup-default-static
> +tests-static += tst-cleanup-default-static
> +tests-special += $(objpfx)tst-cleanup-default-cmp.out $(objpfx)tst-cleanup-default-static-cmp.out
> +LDFLAGS-tst-cleanup-default = -Wl,--gc-sections
> +LDFLAGS-tst-cleanup-default-static = -Wl,--gc-sections
> +
> +ifeq ($(have-gnu-retain)$(have-z-start-stop-gc),yesyes)
> +tests += tst-cleanup-start-stop-gc tst-cleanup-start-stop-gc-static \
> +               tst-cleanup-nostart-stop-gc tst-cleanup-nostart-stop-gc-static
> +tests-static += tst-cleanup-start-stop-gc-static tst-cleanup-nostart-stop-gc-static
> +tests-special += $(objpfx)tst-cleanup-start-stop-gc-cmp.out \
> +               $(objpfx)tst-cleanup-start-stop-gc-static-cmp.out \
> +               $(objpfx)tst-cleanup-nostart-stop-gc-cmp.out \
> +               $(objpfx)tst-cleanup-nostart-stop-gc-static-cmp.out
> +LDFLAGS-tst-cleanup-start-stop-gc := -Wl,--gc-sections,-z,start-stop-gc
> +LDFLAGS-tst-cleanup-start-stop-gc-static := -Wl,--gc-sections,-z,start-stop-gc
> +LDFLAGS-tst-cleanup-nostart-stop-gc := -Wl,--gc-sections,-z,nostart-stop-gc
> +LDFLAGS-tst-cleanup-nostart-stop-gc-static := -Wl,--gc-sections,-z,nostart-stop-gc
> +endif
>   endif
>
>   include ../Rules
> @@ -224,6 +244,14 @@ $(objpfx)tst_wprintf2.out: $(gen-locales)
>   $(objpfx)tst-wfile-sync.out: $(gen-locales)
>   endif
>
> +define gen-tst-cleanup
> +$(objpfx)tst-cleanup-$1-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-$1.out
> +       cmp $$^ > $$@; $$(evaluate-test)
> +endef
> +
> +$(foreach t,default default-static start-stop-gc start-stop-gc-static nostart-stop-gc nostart-stop-gc-static, \
> +  $(eval $(call gen-tst-cleanup,$(t))))
> +
>   $(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen
>         $(SHELL) $< $(common-objpfx) '$(test-program-prefix)'   \
>         $(common-objpfx)libio/; \
> diff --git a/libio/tst-cleanup-default-static.c b/libio/tst-cleanup-default-static.c
> new file mode 100644
> index 0000000000..c39956e2a8
> --- /dev/null
> +++ b/libio/tst-cleanup-default-static.c
> @@ -0,0 +1 @@
> +#include "tst-cleanup.c"
> diff --git a/libio/tst-cleanup-default.c b/libio/tst-cleanup-default.c
> new file mode 100644
> index 0000000000..c39956e2a8
> --- /dev/null
> +++ b/libio/tst-cleanup-default.c
> @@ -0,0 +1 @@
> +#include "tst-cleanup.c"
> diff --git a/libio/tst-cleanup-nostart-stop-gc-static.c b/libio/tst-cleanup-nostart-stop-gc-static.c
> new file mode 100644
> index 0000000000..c39956e2a8
> --- /dev/null
> +++ b/libio/tst-cleanup-nostart-stop-gc-static.c
> @@ -0,0 +1 @@
> +#include "tst-cleanup.c"
> diff --git a/libio/tst-cleanup-nostart-stop-gc.c b/libio/tst-cleanup-nostart-stop-gc.c
> new file mode 100644
> index 0000000000..c39956e2a8
> --- /dev/null
> +++ b/libio/tst-cleanup-nostart-stop-gc.c
> @@ -0,0 +1 @@
> +#include "tst-cleanup.c"
> diff --git a/libio/tst-cleanup-start-stop-gc-static.c b/libio/tst-cleanup-start-stop-gc-static.c
> new file mode 100644
> index 0000000000..c39956e2a8
> --- /dev/null
> +++ b/libio/tst-cleanup-start-stop-gc-static.c
> @@ -0,0 +1 @@
> +#include "tst-cleanup.c"
> diff --git a/libio/tst-cleanup-start-stop-gc.c b/libio/tst-cleanup-start-stop-gc.c
> new file mode 100644
> index 0000000000..c39956e2a8
> --- /dev/null
> +++ b/libio/tst-cleanup-start-stop-gc.c
> @@ -0,0 +1 @@
> +#include "tst-cleanup.c"
> diff --git a/libio/tst-cleanup.c b/libio/tst-cleanup.c
> new file mode 100644
> index 0000000000..837feac164
> --- /dev/null
> +++ b/libio/tst-cleanup.c
> @@ -0,0 +1,34 @@
> +/* Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +/* Test that stdout is flushed after atexit callbacks were run, even if the
> + * executable is linked with --gc-sections.  */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +
> +void
> +hook (void)
> +{
> +  puts ("hello");
> +}
> +
> +int
> +main (void)
> +{
> +  atexit (hook);
> +}
> diff --git a/libio/tst-cleanup.exp b/libio/tst-cleanup.exp
> new file mode 100644
> index 0000000000..ce01362503
> --- /dev/null
> +++ b/libio/tst-cleanup.exp
> @@ -0,0 +1 @@
> +hello
> --
> 2.31.0.208.g409f899ff0-goog
>

LGTM.

Thanks.

-- 
H.J.