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Set the retain attribute on _elf_set_element if CC supports [BZ #27492]
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). Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
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cd6ae7ea54
@ -187,6 +187,9 @@
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/* Define if gcc supports attribute ifunc. */
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/* Define if gcc supports attribute ifunc. */
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#undef HAVE_GCC_IFUNC
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#undef HAVE_GCC_IFUNC
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/* Define if CC supports attribute retain. */
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#undef HAVE_GNU_RETAIN
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/* Define if the linker defines __ehdr_start. */
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/* Define if the linker defines __ehdr_start. */
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#undef HAVE_EHDR_START
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#undef HAVE_EHDR_START
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59
configure
vendored
59
configure
vendored
@ -4105,6 +4105,31 @@ fi
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$as_echo "$libc_cv_textrel_ifunc" >&6; }
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$as_echo "$libc_cv_textrel_ifunc" >&6; }
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# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for GNU attribute retain support" >&5
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$as_echo_n "checking for GNU attribute retain support... " >&6; }
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if ${libc_cv_gnu_retain+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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cat > conftest.c <<EOF
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static int var __attribute__ ((used, retain, section ("__libc_atexit")));
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EOF
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libc_cv_gnu_retain=no
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if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&5 \
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2>&5 ; then
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libc_cv_gnu_retain=yes
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fi
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rm -f conftest*
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gnu_retain" >&5
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$as_echo "$libc_cv_gnu_retain" >&6; }
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if test $libc_cv_gnu_retain = yes; then
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$as_echo "#define HAVE_GNU_RETAIN 1" >>confdefs.h
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fi
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config_vars="$config_vars
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have-gnu-retain = $libc_cv_gnu_retain"
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# Check if gcc warns about alias for function with incompatible types.
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# Check if gcc warns about alias for function with incompatible types.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
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$as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
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$as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
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@ -5871,6 +5896,40 @@ fi
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$as_echo "$libc_linker_feature" >&6; }
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$as_echo "$libc_linker_feature" >&6; }
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z start-stop-gc" >&5
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$as_echo_n "checking for linker that supports -z start-stop-gc... " >&6; }
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libc_linker_feature=no
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if test x"$gnu_ld" = x"yes"; then
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libc_linker_check=`$LD -v --help 2>/dev/null | grep "\-z start-stop-gc"`
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if test -n "$libc_linker_check"; then
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cat > conftest.c <<EOF
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int _start (void) { return 42; }
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EOF
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if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
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-Wl,-z,start-stop-gc -nostdlib -nostartfiles
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-fPIC -shared -o conftest.so conftest.c
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1>&5'
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{ { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
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(eval $ac_try) 2>&5
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ac_status=$?
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$as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
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test $ac_status = 0; }; }
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then
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libc_linker_feature=yes
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fi
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rm -f conftest*
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fi
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fi
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if test $libc_linker_feature = yes; then
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libc_cv_z_start_stop_gc=yes
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else
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libc_cv_z_start_stop_gc=no
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
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$as_echo "$libc_linker_feature" >&6; }
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config_vars="$config_vars
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have-z-start-stop-gc = $libc_cv_z_start_stop_gc"
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
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$as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
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$as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
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libc_linker_feature=no
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libc_linker_feature=no
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21
configure.ac
21
configure.ac
@ -707,6 +707,23 @@ fi
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rm -f conftest*])
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rm -f conftest*])
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AC_SUBST(libc_cv_textrel_ifunc)
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AC_SUBST(libc_cv_textrel_ifunc)
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# Check if CC supports attribute retain as it is used in attribute_used_retain macro.
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AC_CACHE_CHECK([for GNU attribute retain support],
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libc_cv_gnu_retain, [dnl
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cat > conftest.c <<EOF
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static int var __attribute__ ((used, retain, section ("__libc_atexit")));
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EOF
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libc_cv_gnu_retain=no
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if ${CC-cc} -Werror -c conftest.c -o /dev/null 1>&AS_MESSAGE_LOG_FD \
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2>&AS_MESSAGE_LOG_FD ; then
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libc_cv_gnu_retain=yes
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fi
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rm -f conftest*])
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if test $libc_cv_gnu_retain = yes; then
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AC_DEFINE(HAVE_GNU_RETAIN)
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fi
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LIBC_CONFIG_VAR([have-gnu-retain], [$libc_cv_gnu_retain])
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# Check if gcc warns about alias for function with incompatible types.
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# Check if gcc warns about alias for function with incompatible types.
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AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
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AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
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libc_cv_gcc_incompatible_alias, [dnl
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libc_cv_gcc_incompatible_alias, [dnl
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@ -1317,6 +1334,10 @@ LIBC_LINKER_FEATURE([-z execstack], [-Wl,-z,execstack],
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[libc_cv_z_execstack=yes], [libc_cv_z_execstack=no])
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[libc_cv_z_execstack=yes], [libc_cv_z_execstack=no])
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AC_SUBST(libc_cv_z_execstack)
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AC_SUBST(libc_cv_z_execstack)
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LIBC_LINKER_FEATURE([-z start-stop-gc], [-Wl,-z,start-stop-gc],
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[libc_cv_z_start_stop_gc=yes], [libc_cv_z_start_stop_gc=no])
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LIBC_CONFIG_VAR([have-z-start-stop-gc], [$libc_cv_z_start_stop_gc])
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LIBC_LINKER_FEATURE([--no-dynamic-linker],
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LIBC_LINKER_FEATURE([--no-dynamic-linker],
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[-Wl,--no-dynamic-linker],
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[-Wl,--no-dynamic-linker],
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[libc_cv_no_dynamic_linker=yes],
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[libc_cv_no_dynamic_linker=yes],
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@ -352,6 +352,12 @@ for linking")
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*/
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*/
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#ifdef HAVE_GNU_RETAIN
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# define attribute_used_retain __attribute__ ((__used__, __retain__))
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#else
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# define attribute_used_retain __attribute__ ((__used__))
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#endif
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/* Symbol set support macros. */
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/* Symbol set support macros. */
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/* Make SYMBOL, which is in the text segment, an element of SET. */
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/* Make SYMBOL, which is in the text segment, an element of SET. */
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@ -367,12 +373,12 @@ for linking")
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/* When building a shared library, make the set section writable,
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/* When building a shared library, make the set section writable,
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because it will need to be relocated at run time anyway. */
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because it will need to be relocated at run time anyway. */
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# define _elf_set_element(set, symbol) \
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# define _elf_set_element(set, symbol) \
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static const void *__elf_set_##set##_element_##symbol##__ \
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static const void *__elf_set_##set##_element_##symbol##__ \
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__attribute__ ((used, section (#set))) = &(symbol)
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attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
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#else
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#else
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# define _elf_set_element(set, symbol) \
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# define _elf_set_element(set, symbol) \
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static const void *const __elf_set_##set##_element_##symbol##__ \
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static const void *const __elf_set_##set##_element_##symbol##__ \
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__attribute__ ((used, section (#set))) = &(symbol)
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attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
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#endif
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#endif
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/* Define SET as a symbol set. This may be required (it is in a.out) to
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/* Define SET as a symbol set. This may be required (it is in a.out) to
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@ -195,6 +195,26 @@ ifeq (yes,$(build-shared))
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tests-special += $(objpfx)tst-fopenloc-cmp.out $(objpfx)tst-fopenloc-mem.out \
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tests-special += $(objpfx)tst-fopenloc-cmp.out $(objpfx)tst-fopenloc-mem.out \
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$(objpfx)tst-bz24228-mem.out
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$(objpfx)tst-bz24228-mem.out
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endif
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endif
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tests += tst-cleanup-default tst-cleanup-default-static
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tests-static += tst-cleanup-default-static
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tests-special += $(objpfx)tst-cleanup-default-cmp.out $(objpfx)tst-cleanup-default-static-cmp.out
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LDFLAGS-tst-cleanup-default = -Wl,--gc-sections
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LDFLAGS-tst-cleanup-default-static = -Wl,--gc-sections
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ifeq ($(have-gnu-retain)$(have-z-start-stop-gc),yesyes)
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tests += tst-cleanup-start-stop-gc tst-cleanup-start-stop-gc-static \
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tst-cleanup-nostart-stop-gc tst-cleanup-nostart-stop-gc-static
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tests-static += tst-cleanup-start-stop-gc-static tst-cleanup-nostart-stop-gc-static
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tests-special += $(objpfx)tst-cleanup-start-stop-gc-cmp.out \
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$(objpfx)tst-cleanup-start-stop-gc-static-cmp.out \
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$(objpfx)tst-cleanup-nostart-stop-gc-cmp.out \
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$(objpfx)tst-cleanup-nostart-stop-gc-static-cmp.out
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LDFLAGS-tst-cleanup-start-stop-gc := -Wl,--gc-sections,-z,start-stop-gc
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LDFLAGS-tst-cleanup-start-stop-gc-static := -Wl,--gc-sections,-z,start-stop-gc
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LDFLAGS-tst-cleanup-nostart-stop-gc := -Wl,--gc-sections,-z,nostart-stop-gc
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LDFLAGS-tst-cleanup-nostart-stop-gc-static := -Wl,--gc-sections,-z,nostart-stop-gc
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endif
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endif
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endif
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include ../Rules
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include ../Rules
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@ -224,6 +244,14 @@ $(objpfx)tst_wprintf2.out: $(gen-locales)
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$(objpfx)tst-wfile-sync.out: $(gen-locales)
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$(objpfx)tst-wfile-sync.out: $(gen-locales)
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endif
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endif
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define gen-tst-cleanup
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$(objpfx)tst-cleanup-$1-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup-$1.out
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cmp $$^ > $$@; $$(evaluate-test)
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endef
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$(foreach t,default default-static start-stop-gc start-stop-gc-static nostart-stop-gc nostart-stop-gc-static, \
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$(eval $(call gen-tst-cleanup,$(t))))
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$(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen
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$(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen
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$(SHELL) $< $(common-objpfx) '$(test-program-prefix)' \
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$(SHELL) $< $(common-objpfx) '$(test-program-prefix)' \
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$(common-objpfx)libio/; \
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$(common-objpfx)libio/; \
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1
libio/tst-cleanup-default-static.c
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1
libio/tst-cleanup-default-static.c
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@ -0,0 +1 @@
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#include "tst-cleanup.c"
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1
libio/tst-cleanup-default.c
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1
libio/tst-cleanup-default.c
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@ -0,0 +1 @@
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#include "tst-cleanup.c"
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1
libio/tst-cleanup-nostart-stop-gc-static.c
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1
libio/tst-cleanup-nostart-stop-gc-static.c
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@ -0,0 +1 @@
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#include "tst-cleanup.c"
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1
libio/tst-cleanup-nostart-stop-gc.c
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1
libio/tst-cleanup-nostart-stop-gc.c
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@ -0,0 +1 @@
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#include "tst-cleanup.c"
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1
libio/tst-cleanup-start-stop-gc-static.c
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1
libio/tst-cleanup-start-stop-gc-static.c
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@ -0,0 +1 @@
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#include "tst-cleanup.c"
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1
libio/tst-cleanup-start-stop-gc.c
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1
libio/tst-cleanup-start-stop-gc.c
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@ -0,0 +1 @@
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#include "tst-cleanup.c"
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34
libio/tst-cleanup.c
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34
libio/tst-cleanup.c
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@ -0,0 +1,34 @@
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/* Copyright (C) 2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* Test that stdout is flushed after atexit callbacks were run, even if the
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* executable is linked with --gc-sections. */
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#include <stdio.h>
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#include <stdlib.h>
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void
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hook (void)
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{
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puts ("hello");
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}
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int
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main (void)
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{
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atexit (hook);
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}
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1
libio/tst-cleanup.exp
Normal file
1
libio/tst-cleanup.exp
Normal file
@ -0,0 +1 @@
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hello
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