6 files changed, 87 insertions, 2 deletions
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 277ae10..823832f 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -5680,6 +5680,33 @@ AC_DEFUN([GLIBCXX_CHECK_ALIGNAS_CACHELINE], [
   AC_LANG_RESTORE
 ])
 
+dnl
+dnl Check whether iostream initialization should be done in the library,
+dnl using the init_priority attribute.
+dnl
+dnl Defines:
+dnl  _GLIBCXX_USE_INIT_PRIORITY_ATTRIBUTE if GCC supports the init_priority
+dnl    attribute for the target.
+dnl
+AC_DEFUN([GLIBCXX_CHECK_INIT_PRIORITY], [
+AC_LANG_SAVE
+  AC_LANG_CPLUSPLUS
+
+  AC_MSG_CHECKING([whether init_priority attribute is supported])
+  AC_TRY_COMPILE(, [
+  #if ! __has_attribute(init_priority)
+  #error init_priority not supported
+  #endif
+		 ], [ac_init_priority=yes], [ac_init_priority=no])
+  if test "$ac_init_priority" = yes; then
+    AC_DEFINE_UNQUOTED(_GLIBCXX_USE_INIT_PRIORITY_ATTRIBUTE, 1,
+      [Define if init_priority should be used for iostream initialization.])
+  fi
+  AC_MSG_RESULT($ac_init_priority)
+
+  AC_LANG_RESTORE
+])
+
 # Macros from the top-level gcc directory.
 m4_include([../config/gc++filt.m4])
 m4_include([../config/tls.m4])
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index e156650..91eca6e 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -994,6 +994,9 @@
 /* Define if get_nprocs is available in <sys/sysinfo.h>. */
 #undef _GLIBCXX_USE_GET_NPROCS
 
+/* Define if init_priority should be used for iostream initialization. */
+#undef _GLIBCXX_USE_INIT_PRIORITY_ATTRIBUTE
+
 /* Define if LFS support is available. */
 #undef _GLIBCXX_USE_LFS
 
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 98568ae..c8d5508 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -73496,6 +73496,57 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
+# For using init_priority in ios_init.cc
+
+
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether init_priority attribute is supported" >&5
+$as_echo_n "checking whether init_priority attribute is supported... " >&6; }
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  #if ! __has_attribute(init_priority)
+  #error init_priority not supported
+  #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  ac_init_priority=yes
+else
+  ac_init_priority=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+  if test "$ac_init_priority" = yes; then
+
+cat >>confdefs.h <<_ACEOF
+#define _GLIBCXX_USE_INIT_PRIORITY_ATTRIBUTE 1
+_ACEOF
+
+  fi
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_init_priority" >&5
+$as_echo "$ac_init_priority" >&6; }
+
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+
 # Define documentation rules conditionally.
 
 # See if makeinfo has been installed and is modern enough
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 9770c17..fc0f252 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -550,6 +550,9 @@ GLIBCXX_ZONEINFO_DIR
 # For src/c++11/shared_ptr.cc alignment.
 GLIBCXX_CHECK_ALIGNAS_CACHELINE
 
+# For using init_priority in ios_init.cc
+GLIBCXX_CHECK_INIT_PRIORITY
+
 # Define documentation rules conditionally.
 
 # See if makeinfo has been installed and is modern enough
diff --git a/libstdc++-v3/include/std/iostream b/libstdc++-v3/include/std/iostream
index cfd124d..0abf744 100644
--- a/libstdc++-v3/include/std/iostream
+++ b/libstdc++-v3/include/std/iostream
@@ -75,7 +75,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // For construction of filebuffers for cout, cin, cerr, clog et. al.
   // When the init_priority attribute is usable, we do this initialization
   // in the compiled library instead (src/c++98/globals_io.cc).
-#if !__has_attribute(__init_priority__)
+#if !(_GLIBCXX_USE_INIT_PRIORITY_ATTRIBUTE \
+      && __has_attribute(__init_priority__))
   static ios_base::Init __ioinit;
 #elif defined(_GLIBCXX_SYMVER_GNU)
   __extension__ __asm (".globl _ZSt21ios_base_library_initv");
diff --git a/libstdc++-v3/src/c++98/ios_base_init.h b/libstdc++-v3/src/c++98/ios_base_init.h
index b600ec3..f7edfc8 100644
--- a/libstdc++-v3/src/c++98/ios_base_init.h
+++ b/libstdc++-v3/src/c++98/ios_base_init.h
@@ -8,6 +8,6 @@
 // constructor when statically linking with libstdc++.a), instead of
 // doing so in (each TU that includes) <iostream>.
 // This needs to be done in the same TU that defines the stream objects.
-#if __has_attribute(init_priority)
+#if _GLIBCXX_USE_INIT_PRIORITY_ATTRIBUTE
 static ios_base::Init __ioinit __attribute__((init_priority(90)));
 #endif