From 14b295bdb00305370ec0aaad7f4319bad55ad6e9 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Wed, 17 Jan 2018 09:40:27 +0300
Subject: Add workaround for data race in libstdc++'s ctype<char>::narrow()

---
 build2/b.cxx | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

(limited to 'build2/b.cxx')

diff --git a/build2/b.cxx b/build2/b.cxx
index c7219f0..1106031 100644
--- a/build2/b.cxx
+++ b/build2/b.cxx
@@ -10,6 +10,10 @@
 
 #include <stdlib.h>    // getenv() _putenv()(_WIN32)
 
+#ifdef __GLIBCXX__
+#  include <locale>
+#endif
+
 #include <sstream>
 #include <cstring>     // strcmp(), strchr()
 #include <typeinfo>
@@ -152,6 +156,22 @@ main (int argc, char* argv[])
   }
 #endif
 
+// A data race happens in the libstdc++ (as of GCC 7.2) implementation of the
+// ctype<char>::narrow() function (bug #77704). The issue is easily triggered
+// by the testscript runner that indirectly (via regex) uses ctype<char> facet
+// of the global locale (and can potentially be triggered by other locale-
+// aware code). We work around this by pre-initializing the global locale
+// facet internal cache.
+//
+#ifdef __GLIBCXX__
+  {
+    const ctype<char>& ct (use_facet<ctype<char>> (locale ()));
+
+    for (size_t i (0); i != 256; ++i)
+      ct.narrow (static_cast<char> (i), '\0');
+  }
+#endif
+
   try
   {
     // On POSIX ignore SIGPIPE which is signaled to a pipe-writing process if
-- 
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