From f52b47eea4c5de553d202669f91e6f4f14668592 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Mon, 1 Jul 2019 23:35:27 +0300
Subject: Add workaround for data race in libstdc++'s locale(const locale&,
 Facet*) constructor

---
 build2/test/script/regex.cxx      | 35 +++++++++++++++++++++++++++++++++--
 build2/test/script/regex.hxx      |  7 +++++++
 build2/test/script/regex.test.cxx |  3 ++-
 3 files changed, 42 insertions(+), 3 deletions(-)

(limited to 'build2/test/script')

diff --git a/build2/test/script/regex.cxx b/build2/test/script/regex.cxx
index 6b15266..bbd1738 100644
--- a/build2/test/script/regex.cxx
+++ b/build2/test/script/regex.cxx
@@ -2,6 +2,8 @@
 // copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
+#include <locale>
+
 #include <build2/test/script/regex.hxx>
 
 using namespace std;
@@ -163,11 +165,40 @@ namespace build2
 
         // line_char_locale
         //
+
+        // An exemplar locale with the std::ctype<line_char> facet.  It is
+        // used for the subsequent line char locale objects creation (see
+        // below) which normally ends up with a shallow copy of a reference-
+        // counted object.
+        //
+        // Note that creating the line char locales from the exemplar is not
+        // merely an optimization: there is a data race in the libstdc++ (at
+        // least as of GCC 9.1) implementation of the locale(const locale&,
+        // Facet*) constructor (bug #91057).
+        //
+        // Also note that we install the facet in init() rather than during
+        // the object creation to avoid a race with the std::locale-related
+        // global variables initialization.
+        //
+        static locale line_char_locale_exemplar;
+
+        void
+        init ()
+        {
+          line_char_locale_exemplar =
+            locale (locale (),
+                    new std::ctype<line_char> ()); // Hidden by ctype bitmask.
+        }
+
         line_char_locale::
         line_char_locale ()
-            : locale (locale (),
-                      new std::ctype<line_char> ()) // Hidden by ctype bitmask.
+            : locale (line_char_locale_exemplar)
         {
+          // Make sure init() has been called.
+          //
+          // Note: has_facet() is hidden by a private function in libc++.
+          //
+          assert (std::has_facet<std::ctype<line_char>> (*this));
         }
 
         // char_regex
diff --git a/build2/test/script/regex.hxx b/build2/test/script/regex.hxx
index 500c21b..33a4cba 100644
--- a/build2/test/script/regex.hxx
+++ b/build2/test/script/regex.hxx
@@ -344,6 +344,13 @@ namespace build2
           //
           line_char_locale ();
         };
+
+        // Initialize the testscript regex global state. Should be called once
+        // prior to creating objects of types from this namespace. Note: not
+        // thread-safe.
+        //
+        void
+        init ();
       }
     }
   }
diff --git a/build2/test/script/regex.test.cxx b/build2/test/script/regex.test.cxx
index 7b89e4d..1e48f97 100644
--- a/build2/test/script/regex.test.cxx
+++ b/build2/test/script/regex.test.cxx
@@ -19,6 +19,8 @@ main ()
   using cf = char_flags;
   using cr = char_regex;
 
+  init (); // Initializes the testscript regex global state.
+
   // Test line_char.
   //
   {
@@ -183,7 +185,6 @@ main ()
     using ct = ctype<lc>;
 
     line_char_locale l;
-    assert (has_facet<ct> (l));
 
     // It is better not to create q facet on stack as it is
     // reference-countable.
-- 
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