diff --git a/libcxx/src/iostream.cpp b/libcxx/src/iostream.cpp
--- a/libcxx/src/iostream.cpp
+++ b/libcxx/src/iostream.cpp
@@ -77,7 +77,17 @@
 #endif
 ;
 
-_LIBCPP_HIDDEN ios_base::Init __start_std_streams;
+// Detect if the init_priority attribute is supported.
+#if (defined(_LIBCPP_COMPILER_GCC) && defined(__APPLE__)) \
+  || defined(_LIBCPP_COMPILER_MSVC)
+// GCC on Apple doesn't support the init priority attribute,
+// and MSVC doesn't support any GCC attributes.
+# define _LIBCPP_INIT_PRIORITY_MAX
+#else
+# define _LIBCPP_INIT_PRIORITY_MAX __attribute__((init_priority(101)))
+#endif
+
+_LIBCPP_HIDDEN ios_base::Init __start_std_streams _LIBCPP_INIT_PRIORITY_MAX;
 
 // On Windows the TLS storage for locales needs to be initialized before we create
 // the standard streams, otherwise it may not be alive during program termination