[gcc r11-6072] libstdc++: Use init_priority attribute for Init object [PR 98108]

[Jonathan Wakely]

https://gcc.gnu.org/g:cf4ed3b41594b6935a337fe0aaf8149eadf88751

commit r11-6072-gcf4ed3b41594b6935a337fe0aaf8149eadf88751
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Dec 15 11:40:06 2020 +0000

    libstdc++: Use init_priority attribute for Init object [PR 98108]
    
    This causes the global objects that run the <iostream> initialization
    code to be constructed earlier, which avoids some bugs in user code due
    to incorrectly relying on static initialization order.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/98108
            * include/std/iostream (__ioinit): Add init_priority attribute.

Diff:
---
 libstdc++-v3/include/std/iostream | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/iostream b/libstdc++-v3/include/std/iostream
index f988342b90a..6b2f964f688 100644
--- a/libstdc++-v3/include/std/iostream
+++ b/libstdc++-v3/include/std/iostream
@@ -70,8 +70,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #endif
   //@}
 
+#if __has_attribute(__init_priority__)
+# define _GLIBCXX_INIT_PRIO(N) __attribute__((__init_priority__(N)))
+#else
+# define _GLIBCXX_INIT_PRIO(N)
+#endif
+
   // For construction of filebuffers for cout, cin, cerr, clog et. al.
-  static ios_base::Init __ioinit;
+  static ios_base::Init __ioinit _GLIBCXX_INIT_PRIO(90);
+
+#undef _GLIBCXX_INIT_PRIO
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace