Factor out thread model detection with new GCC_AC_THREAD_MODEL macro

This macro deduplicates the $CC -v 2>&1 | sed -n 's/^Thread model: //p' check that was occurring in various runtime libs. Additionally, as a bit of an Easter egg, this also allows overriding what the compiler would return by setting the `gcc_cv_target_thread_file` cache variable first. I admit that it is in fact this Easter egg that led me to write the patch. The use-case for it is for making multilib builds where the library sets do not all share the same thread model easier. See also `THREAD_MODEL_SPEC` for more about the varying thread models use-case. Arguably one could could try to define on `THREAD_MODEL_SPEC` on more platforms (besides e.g. AIX) but the ramifications of this are a bit unclear. Setting `gcc_cv_target_thread_file` directly is a "low tech" solution that will work for now for sure. Of course, since setting a cache variable like this a hacky trick, I will not expect this to be at all stable/guaranteed to work, going forward. Thanks to Arsen who on IRC discussed these things with me, including in particular making it a cache var not `--with-model` flag, to not prematurely foster expectations that this is stable. Suggested-by: Arsen Arsenović <arsen@aarsen.me> config/ChangeLog: * gthr.m4: Create new GCC_AC_THREAD_MODEL macro libatomic/ChangeLog: * Makefile.in: Regenerate. * aclocal.m4: Regenerate. * configure: Regenerate. * configure.ac: Use GCC_AC_THREAD_MODEL instead of hand-rolled * testsuite/Makefile.in: Regenerate. libgcc/ChangeLog: * configure: Regenerate. * configure.ac: Use GCC_AC_THREAD_MODEL instead of hand-rolled libphobos/ChangeLog: * configure: Regenerate. * m4/druntime/os.m4: Use AC_MSG_ERROR, not private as_fn_error libstdc++-v3/ChangeLog: * acinclude.m4: Use GCC_AC_THREAD_MODEL instead, via AC_REQUIRE * configure: Regenerate.
2026-01-12 00:05:41 +08:00 · 2025-12-09 22:06:48 +00:00
parent 1dd44ebd5f
commit e5d853bbe9
12 changed files with 129 additions and 51 deletions
--- a/config/gthr.m4
+++ b/config/gthr.m4
@@ -5,6 +5,26 @@ dnl Public License, this file may be distributed as part of a program
 dnl that contains a configuration script generated by Autoconf, under
 dnl the same distribution terms as the rest of that program.

+dnl Define thread model
+
+dnl usage: GCC_AC_THREAD_MODEL
+AC_DEFUN([GCC_AC_THREAD_MODEL],
+[
+# Specify the threading model for this GCC runtime library
+# Pass with no value to take from compiler's metadata
+# Pass with a value to specify a thread package
+# 'single' means single threaded -- without threads.
+AC_CACHE_CHECK([for the threading model used by GCC], [gcc_cv_target_thread_file], [
+  # Set new cache variable
+  gcc_cv_target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
+])
+# Set variable name (not prefixed enough to be a good cache variable
+# name) traditionally used for this purpose, to avoid having to change
+# a bunch of configure scripts.
+target_thread_file="$gcc_cv_target_thread_file"
+])
+
+
 dnl Define header location by thread model

 dnl usage: GCC_AC_THREAD_HEADER([thread_model])
@@ -23,6 +43,9 @@ case $1 in
    vxworks)	thread_header=config/gthr-vxworks.h ;;
    win32)	thread_header=config/i386/gthr-win32.h ;;
    mcf)	thread_header=config/i386/gthr-mcf.h ;;
+    *)
+        AC_MSG_ERROR([No known header for threading model '$1'.])
+        ;;
 esac
 AC_SUBST(thread_header)
 ])
--- a/libatomic/Makefile.in
+++ b/libatomic/Makefile.in
@@ -108,6 +108,7 @@ am__aclocal_m4_deps = $(top_srcdir)/../config/acx.m4 \
 	$(top_srcdir)/../config/clang-plugin.m4 \
 	$(top_srcdir)/../config/depstand.m4 \
 	$(top_srcdir)/../config/gcc-plugin.m4 \
+	$(top_srcdir)/../config/gthr.m4 \
 	$(top_srcdir)/../config/lead-dot.m4 \
 	$(top_srcdir)/../config/lthostflags.m4 \
 	$(top_srcdir)/../config/multi.m4 \
@@ -171,7 +172,7 @@ libatomic_la_OBJECTS = $(am_libatomic_la_OBJECTS)
 AM_V_lt = $(am__v_lt_@AM_V@)
 am__v_lt_ = $(am__v_lt_@AM_DEFAULT_V@)
 am__v_lt_0 = --silent
-am__v_lt_1 = 
+am__v_lt_1 =
 libatomic_la_LINK = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
 	$(LIBTOOLFLAGS) --mode=link $(CCLD) $(AM_CFLAGS) $(CFLAGS) \
 	$(libatomic_la_LDFLAGS) $(LDFLAGS) -o $@
@@ -192,11 +193,11 @@ am__v_P_1 = :
 AM_V_GEN = $(am__v_GEN_@AM_V@)
 am__v_GEN_ = $(am__v_GEN_@AM_DEFAULT_V@)
 am__v_GEN_0 = @echo "  GEN     " $@;
-am__v_GEN_1 = 
+am__v_GEN_1 =
 AM_V_at = $(am__v_at_@AM_V@)
 am__v_at_ = $(am__v_at_@AM_DEFAULT_V@)
 am__v_at_0 = @
-am__v_at_1 = 
+am__v_at_1 =
 depcomp = $(SHELL) $(top_srcdir)/../depcomp
 am__depfiles_maybe = depfiles
 am__mv = mv -f
@@ -209,7 +210,7 @@ LTCPPASCOMPILE = $(LIBTOOL) $(AM_V_lt) $(AM_LIBTOOLFLAGS) \
 AM_V_CPPAS = $(am__v_CPPAS_@AM_V@)
 am__v_CPPAS_ = $(am__v_CPPAS_@AM_DEFAULT_V@)
 am__v_CPPAS_0 = @echo "  CPPAS   " $@;
-am__v_CPPAS_1 = 
+am__v_CPPAS_1 =
 COMPILE = $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
 	$(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
 LTCOMPILE = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
@@ -219,7 +220,7 @@ LTCOMPILE = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
 AM_V_CC = $(am__v_CC_@AM_V@)
 am__v_CC_ = $(am__v_CC_@AM_DEFAULT_V@)
 am__v_CC_0 = @echo "  CC      " $@;
-am__v_CC_1 = 
+am__v_CC_1 =
 CCLD = $(CC)
 LINK = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
 	$(LIBTOOLFLAGS) --mode=link $(CCLD) $(AM_CFLAGS) $(CFLAGS) \
@@ -227,7 +228,7 @@ LINK = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
 AM_V_CCLD = $(am__v_CCLD_@AM_V@)
 am__v_CCLD_ = $(am__v_CCLD_@AM_DEFAULT_V@)
 am__v_CCLD_0 = @echo "  CCLD    " $@;
-am__v_CCLD_1 = 
+am__v_CCLD_1 =
 SOURCES = $(libatomic_la_SOURCES) $(EXTRA_libatomic_la_SOURCES) \
 	$(libatomic_convenience_la_SOURCES)
 RECURSIVE_TARGETS = all-recursive check-recursive cscopelist-recursive \
@@ -422,10 +423,10 @@ AM_CCASFLAGS = $(XCFLAGS)
 AM_LDFLAGS = $(XLDFLAGS) $(SECTION_LDFLAGS) $(OPT_LDFLAGS)
 toolexeclib_LTLIBRARIES = libatomic.la
 noinst_LTLIBRARIES = libatomic_convenience.la
-@LIBAT_BUILD_VERSIONED_SHLIB_FALSE@libatomic_version_script = 
+@LIBAT_BUILD_VERSIONED_SHLIB_FALSE@libatomic_version_script =
@LIBAT_BUILD_VERSIONED_SHLIB_GNU_TRUE@@LIBAT_BUILD_VERSIONED_SHLIB_TRUE@libatomic_version_script = -Wl,--version-script,$(top_srcdir)/libatomic.map
@LIBAT_BUILD_VERSIONED_SHLIB_SUN_TRUE@@LIBAT_BUILD_VERSIONED_SHLIB_TRUE@libatomic_version_script = -Wl,-M,libatomic.map-sun
-@LIBAT_BUILD_VERSIONED_SHLIB_FALSE@libatomic_version_dep = 
+@LIBAT_BUILD_VERSIONED_SHLIB_FALSE@libatomic_version_dep =
@LIBAT_BUILD_VERSIONED_SHLIB_GNU_TRUE@@LIBAT_BUILD_VERSIONED_SHLIB_TRUE@libatomic_version_dep = $(top_srcdir)/libatomic.map
@LIBAT_BUILD_VERSIONED_SHLIB_SUN_TRUE@@LIBAT_BUILD_VERSIONED_SHLIB_TRUE@libatomic_version_dep = libatomic.map-sun
 libatomic_version_info = -version-info $(libtool_VERSION)
@@ -443,7 +444,7 @@ libatomic_la_LDFLAGS = $(libatomic_version_info) $(libatomic_version_script) \
@PARTIAL_VXWORKS_FALSE@SIZEOBJS = load store cas exch fadd fsub fand fior fxor fnand tas
@PARTIAL_VXWORKS_FALSE@EXTRA_libatomic_la_SOURCES = $(addsuffix _n.c,$(SIZEOBJS))
@PARTIAL_VXWORKS_FALSE@libatomic_la_DEPENDENCIES = $(libatomic_la_LIBADD) $(libatomic_version_dep)
-@PARTIAL_VXWORKS_FALSE@empty = 
+@PARTIAL_VXWORKS_FALSE@empty =
@PARTIAL_VXWORKS_FALSE@space = $(empty) $(empty)
@PARTIAL_VXWORKS_FALSE@PAT_SPLIT = $(subst _,$(space),$(*F))
@PARTIAL_VXWORKS_FALSE@PAT_BASE = $(word 1,$(PAT_SPLIT))
@@ -452,7 +453,7 @@ libatomic_la_LDFLAGS = $(libatomic_version_info) $(libatomic_version_script) \
@PARTIAL_VXWORKS_FALSE@IFUNC_DEF = -DIFUNC_ALT=$(PAT_S)
@PARTIAL_VXWORKS_FALSE@IFUNC_OPT = $(subst |,$(space),$(word $(PAT_S),$(IFUNC_OPTIONS)))
@PARTIAL_VXWORKS_FALSE@@AMDEP_TRUE@M_DEPS = -MT $@ -MD -MP -MF $(DEPDIR)/$(@F).Ppo
-@PARTIAL_VXWORKS_FALSE@@AMDEP_FALSE@M_DEPS = 
+@PARTIAL_VXWORKS_FALSE@@AMDEP_FALSE@M_DEPS =
@PARTIAL_VXWORKS_FALSE@M_SIZE = -DN=$(PAT_N)
@PARTIAL_VXWORKS_FALSE@M_IFUNC = $(if $(PAT_S),$(IFUNC_DEF) $(IFUNC_OPT))
@PARTIAL_VXWORKS_FALSE@M_FILE = $(PAT_BASE)_n.c
@@ -485,10 +486,10 @@ libatomic_convenience_la_LIBADD = $(libatomic_la_LIBADD)
 # built after libatomic, which makes RPATH insecure. Removing libatomic.la
 # from $gcc_objdir seems to fix the issue.
 gcc_objdir = `pwd`/$(MULTIBUILDTOP)../../gcc/
-MULTISRCTOP = 
-MULTIBUILDTOP = 
-MULTIDIRS = 
-MULTISUBDIR = 
+MULTISRCTOP =
+MULTIBUILDTOP =
+MULTIDIRS =
+MULTISUBDIR =
 MULTIDO = true
 MULTICLEAN = true
 all: auto-config.h
@@ -538,7 +539,7 @@ auto-config.h: stamp-h1
 stamp-h1: $(srcdir)/auto-config.h.in $(top_builddir)/config.status
 	@rm -f stamp-h1
 	cd $(top_builddir) && $(SHELL) ./config.status auto-config.h
-$(srcdir)/auto-config.h.in: @MAINTAINER_MODE_TRUE@ $(am__configure_deps) 
+$(srcdir)/auto-config.h.in: @MAINTAINER_MODE_TRUE@ $(am__configure_deps)
 	($(am__cd) $(top_srcdir) && $(AUTOHEADER))
 	rm -f stamp-h1
 	touch $@
@@ -592,10 +593,10 @@ clean-toolexeclibLTLIBRARIES:
 	  rm -f $${locs}; \
 	}

-libatomic.la: $(libatomic_la_OBJECTS) $(libatomic_la_DEPENDENCIES) $(EXTRA_libatomic_la_DEPENDENCIES) 
+libatomic.la: $(libatomic_la_OBJECTS) $(libatomic_la_DEPENDENCIES) $(EXTRA_libatomic_la_DEPENDENCIES)
 	$(AM_V_CCLD)$(libatomic_la_LINK) -rpath $(toolexeclibdir) $(libatomic_la_OBJECTS) $(libatomic_la_LIBADD) $(LIBS)

-libatomic_convenience.la: $(libatomic_convenience_la_OBJECTS) $(libatomic_convenience_la_DEPENDENCIES) $(EXTRA_libatomic_convenience_la_DEPENDENCIES) 
+libatomic_convenience.la: $(libatomic_convenience_la_OBJECTS) $(libatomic_convenience_la_DEPENDENCIES) $(EXTRA_libatomic_convenience_la_DEPENDENCIES)
 	$(AM_V_CCLD)$(LINK)  $(libatomic_convenience_la_OBJECTS) $(libatomic_convenience_la_LIBADD) $(LIBS)

 mostlyclean-compile:
--- a/libatomic/aclocal.m4
+++ b/libatomic/aclocal.m4
@@ -1191,6 +1191,7 @@ m4_include([../config/acx.m4])
 m4_include([../config/clang-plugin.m4])
 m4_include([../config/depstand.m4])
 m4_include([../config/gcc-plugin.m4])
+m4_include([../config/gthr.m4])
 m4_include([../config/lead-dot.m4])
 m4_include([../config/lthostflags.m4])
 m4_include([../config/multi.m4])
--- a/libatomic/configure
+++ b/libatomic/configure
@@ -12254,11 +12254,28 @@ libtool_VERSION=3:0:2


 # Check for used threading-model
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for thread model used by GCC" >&5
-$as_echo_n "checking for thread model used by GCC... " >&6; }
-target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $target_thread_file" >&5
-$as_echo "$target_thread_file" >&6; }
+
+# Specify the threading model for this GCC runtime library
+# Pass with no value to take from compiler's metadata
+# Pass with a value to specify a thread package
+# 'single' means single threaded -- without threads.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for the threading model used by GCC" >&5
+$as_echo_n "checking for the threading model used by GCC... " >&6; }
+if ${gcc_cv_target_thread_file+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+  # Set new cache variable
+  gcc_cv_target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_target_thread_file" >&5
+$as_echo "$gcc_cv_target_thread_file" >&6; }
+# Set variable name (not prefixed enough to be a good cache variable
+# name) traditionally used for this purpose, to avoid having to change
+# a bunch of configure scripts.
+target_thread_file="$gcc_cv_target_thread_file"
+

 case "$target" in
 *aarch64*)
--- a/libatomic/configure.ac
+++ b/libatomic/configure.ac
@@ -177,9 +177,7 @@ libtool_VERSION=3:0:2
 AC_SUBST(libtool_VERSION)

 # Check for used threading-model
-AC_MSG_CHECKING([for thread model used by GCC])
-target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
-AC_MSG_RESULT([$target_thread_file])
+GCC_AC_THREAD_MODEL

 case "$target" in
 *aarch64*)
--- a/libatomic/testsuite/Makefile.in
+++ b/libatomic/testsuite/Makefile.in
@@ -94,6 +94,7 @@ am__aclocal_m4_deps = $(top_srcdir)/../config/acx.m4 \
 	$(top_srcdir)/../config/clang-plugin.m4 \
 	$(top_srcdir)/../config/depstand.m4 \
 	$(top_srcdir)/../config/gcc-plugin.m4 \
+	$(top_srcdir)/../config/gthr.m4 \
 	$(top_srcdir)/../config/lead-dot.m4 \
 	$(top_srcdir)/../config/lthostflags.m4 \
 	$(top_srcdir)/../config/multi.m4 \
@@ -120,11 +121,11 @@ am__v_P_1 = :
 AM_V_GEN = $(am__v_GEN_@AM_V@)
 am__v_GEN_ = $(am__v_GEN_@AM_DEFAULT_V@)
 am__v_GEN_0 = @echo "  GEN     " $@;
-am__v_GEN_1 = 
+am__v_GEN_1 =
 AM_V_at = $(am__v_at_@AM_V@)
 am__v_at_ = $(am__v_at_@AM_DEFAULT_V@)
 am__v_at_0 = @
-am__v_at_1 = 
+am__v_at_1 =
 SOURCES =
 am__can_run_installinfo = \
  case $$AM_UPDATE_INFO_DIR in \
--- a/libgcc/configure
+++ b/libgcc/configure
@@ -5046,11 +5046,28 @@ $as_echo "$acl_cv_prog_gnu_ld" >&6; }
 with_gnu_ld=$acl_cv_prog_gnu_ld


-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for thread model used by GCC" >&5
-$as_echo_n "checking for thread model used by GCC... " >&6; }
-target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $target_thread_file" >&5
-$as_echo "$target_thread_file" >&6; }
+
+# Specify the threading model for this GCC runtime library
+# Pass with no value to take from compiler's metadata
+# Pass with a value to specify a thread package
+# 'single' means single threaded -- without threads.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for the threading model used by GCC" >&5
+$as_echo_n "checking for the threading model used by GCC... " >&6; }
+if ${gcc_cv_target_thread_file+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+  # Set new cache variable
+  gcc_cv_target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_target_thread_file" >&5
+$as_echo "$gcc_cv_target_thread_file" >&6; }
+# Set variable name (not prefixed enough to be a good cache variable
+# name) traditionally used for this purpose, to avoid having to change
+# a bunch of configure scripts.
+target_thread_file="$gcc_cv_target_thread_file"
+

 # Check for assembler CFI support.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether assembler supports CFI directives" >&5
@@ -5737,6 +5754,9 @@ case $target_thread_file in
    vxworks)	thread_header=config/gthr-vxworks.h ;;
    win32)	thread_header=config/i386/gthr-win32.h ;;
    mcf)	thread_header=config/i386/gthr-mcf.h ;;
+    *)
+        as_fn_error $? "No known header for threading model '$target_thread_file'." "$LINENO" 5
+        ;;
 esac


--- a/libgcc/configure.ac
+++ b/libgcc/configure.ac
@@ -305,9 +305,7 @@ AC_SUBST([use_tm_clone_registry])

 AC_LIB_PROG_LD_GNU

-AC_MSG_CHECKING([for thread model used by GCC])
-target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
-AC_MSG_RESULT([$target_thread_file]) 
+GCC_AC_THREAD_MODEL

 # Check for assembler CFI support.
 AC_CACHE_CHECK([whether assembler supports CFI directives], [libgcc_cv_cfi],
--- a/libphobos/configure
+++ b/libphobos/configure
@@ -14920,7 +14920,7 @@ case $d_thread_model in
    # TODO: These targets need porting.
    dce|mipssde|rtems|tpf|vxworks)
 	    DCFG_THREAD_MODEL="Single" ;;
-    *)	    as_fn_error "Thread implementation '$d_thread_model' not recognised" "$LINENO" 5 ;;
+    *)	    as_fn_error $? "Thread implementation '$d_thread_model' not recognised" "$LINENO" 5 ;;
 esac


--- a/libphobos/m4/druntime/os.m4
+++ b/libphobos/m4/druntime/os.m4
@@ -32,7 +32,7 @@ case $1 in
    # TODO: These targets need porting.
    dce|mipssde|rtems|tpf|vxworks)
 	    DCFG_THREAD_MODEL="Single" ;;
-    *)	    as_fn_error "Thread implementation '$1' not recognised" "$LINENO" 5 ;;
+    *)	    AC_MSG_ERROR([Thread implementation '$1' not recognised]) ;;
 esac
 AC_SUBST(DCFG_THREAD_MODEL)
 ])
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4193,9 +4193,7 @@ dnl Substs:
 dnl  thread_header
 dnl
 AC_DEFUN([GLIBCXX_ENABLE_THREADS], [
-  AC_MSG_CHECKING([for thread model used by GCC])
-  target_thread_file=`$CXX -v 2>&1 | sed -n 's/^Thread model: //p'`
-  AC_MSG_RESULT([$target_thread_file])
+  AC_REQUIRE([GCC_AC_THREAD_MODEL])
  GCC_AC_THREAD_HEADER([$target_thread_file])
 ])

@@ -4208,6 +4206,7 @@ dnl
 dnl GLIBCXX_ENABLE_SYMVERS must be done before this.
 dnl
 AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
+  AC_REQUIRE([GCC_AC_THREAD_MODEL])
  GLIBCXX_ENABLE(libstdcxx-threads,auto,,[enable C++11 threads support])

  if test x$enable_libstdcxx_threads = xauto ||
@@ -4220,7 +4219,6 @@ AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
  CXXFLAGS="$CXXFLAGS -fno-exceptions \
 	-I${toplevel_srcdir}/libgcc -I${toplevel_builddir}/libgcc"

-  target_thread_file=`$CXX -v 2>&1 | sed -n 's/^Thread model: //p'`
  case $target_thread_file in
    posix)
      CXXFLAGS="$CXXFLAGS -DSUPPORTS_WEAK -DGTHREAD_USE_WEAK -D_PTHREADS"
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -16330,11 +16330,29 @@ $as_echo "$enable_libstdcxx_pch" >&6; }



-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for thread model used by GCC" >&5
-$as_echo_n "checking for thread model used by GCC... " >&6; }
-  target_thread_file=`$CXX -v 2>&1 | sed -n 's/^Thread model: //p'`
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $target_thread_file" >&5
-$as_echo "$target_thread_file" >&6; }
+# Specify the threading model for this GCC runtime library
+# Pass with no value to take from compiler's metadata
+# Pass with a value to specify a thread package
+# 'single' means single threaded -- without threads.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for the threading model used by GCC" >&5
+$as_echo_n "checking for the threading model used by GCC... " >&6; }
+if ${gcc_cv_target_thread_file+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+  # Set new cache variable
+  gcc_cv_target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_target_thread_file" >&5
+$as_echo "$gcc_cv_target_thread_file" >&6; }
+# Set variable name (not prefixed enough to be a good cache variable
+# name) traditionally used for this purpose, to avoid having to change
+# a bunch of configure scripts.
+target_thread_file="$gcc_cv_target_thread_file"
+
+
+

 case $target_thread_file in
    aix)	thread_header=config/rs6000/gthr-aix.h ;;
@@ -16349,6 +16367,9 @@ case $target_thread_file in
    vxworks)	thread_header=config/gthr-vxworks.h ;;
    win32)	thread_header=config/i386/gthr-win32.h ;;
    mcf)	thread_header=config/i386/gthr-mcf.h ;;
+    *)
+        as_fn_error $? "No known header for threading model '$target_thread_file'." "$LINENO" 5
+        ;;
 esac


@@ -16422,7 +16443,7 @@ $as_echo "$glibcxx_cv_atomic_word" >&6; }
    # Fake what AC_TRY_COMPILE does.

    cat > conftest.$ac_ext << EOF
-#line 16425 "configure"
+#line 16446 "configure"
 #include "${glibcxx_srcdir}/config/$atomic_word_dir/atomic_word.h"
 int main()
 {
@@ -16568,7 +16589,7 @@ $as_echo "mutex" >&6; }
  # unnecessary for this test.

    cat > conftest.$ac_ext << EOF
-#line 16571 "configure"
+#line 16592 "configure"
 int main()
 {
  _Decimal32 d1;
@@ -16610,7 +16631,7 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
  # unnecessary for this test.

  cat > conftest.$ac_ext << EOF
-#line 16613 "configure"
+#line 16634 "configure"
 template<typename T1, typename T2>
  struct same
  { typedef T2 type; };
@@ -52252,6 +52273,7 @@ done

 # For gthread support.  Depends on GLIBCXX_ENABLE_SYMVERS.

+
   # Check whether --enable-libstdcxx-threads was given.
 if test "${enable_libstdcxx_threads+set}" = set; then :
  enableval=$enable_libstdcxx_threads;
@@ -52281,7 +52303,6 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
  CXXFLAGS="$CXXFLAGS -fno-exceptions \
 	-I${toplevel_srcdir}/libgcc -I${toplevel_builddir}/libgcc"

-  target_thread_file=`$CXX -v 2>&1 | sed -n 's/^Thread model: //p'`
  case $target_thread_file in
    posix)
      CXXFLAGS="$CXXFLAGS -DSUPPORTS_WEAK -DGTHREAD_USE_WEAK -D_PTHREADS"
@@ -53969,7 +53990,7 @@ $as_echo "$glibcxx_cv_libbacktrace_atomics" >&6; }
    CXXFLAGS='-O0 -S'

    cat > conftest.$ac_ext << EOF
-#line 53972 "configure"
+#line 53993 "configure"
 #include <stddef.h>
 int main()
 {