libstdc++: Fix iostream init for Clang on darwin [PR110432]

The __has_attribute(init_priority) check in <iostream> is true for Clang
on darwin, which means that user code including <iostream> thinks the
library will initialize the global streams. However, when libstdc++ is
built by GCC on darwin, the __has_attribute(init_priority) check is
false, which means that the library thinks that user code will do the
initialization when <iostream> is included. This means that the
initialization is never done.

Add an autoconf check so that the header and the library both make their
decision based on the static properties of GCC at build time, with a
consistent outcome.

As a belt and braces check, also do the initialization in <iostream> if
the compiler including that header doesn't support the attribute (even
if the library also containers the initialization). This might result in
redundant initialization done in <iostream>, but ensures the
initialization happens somewhere if there's any doubt about the
attribute working correctly due to missing linker support.

libstdc++-v3/ChangeLog:

	PR libstdc++/110432
	* acinclude.m4 (GLIBCXX_CHECK_INIT_PRIORITY): New.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Use GLIBCXX_CHECK_INIT_PRIORITY.
	* include/std/iostream: Use new autoconf macro as well as
	__has_attribute.
	* src/c++98/ios_base_init.h: Use new autoconf macro instead of
	__has_attribute.

Reviewed-by: Patrick Palka <ppalka@redhat.com>

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 277ae10e031a27c16354e3902a3bd7ea19780f53..823832f97d4f47d1161fe5e4d0dcd5c491305e8b 100644 (file)
--- 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 e156650792ed63024aa32fc66660d6691236216b..91eca6ef60874b39f72610e0666c8a8c122f92f2 100644 (file)
--- 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 98568ae0c30bc4d27c7a402614c3c07c55ff2139..c8d55083cd7cdd832f302f8d95bd07b7c5d63b50 100755 (executable)
--- 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 9770c1787679ff011e53299d6c222fb4378961ab..fc0f25220277294e3130f985acc5db7634412d90 100644 (file)
--- 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 cfd124dcf432e40b7151be2e4660297b4cb05082..0abf7445f58b960c7f35db75f31f211642fe4900 100644 (file)
--- 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 b600ec3298e45f252a8231a087be911a4aaefc66..f7edfc846258db6b3ad5a5f478bbc15182db0d8c 100644 (file)
--- 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