Work around static initialization order issue

value_traits<T>::value_type initialization is not constexpr in VC because
of pointers to function template instantiations (which apparently are not
constexpr).

3 files changed, 39 insertions, 10 deletions

diff --git a/build2/variable b/build2/variable
index adc11fa..a63b5b4 100644
--- a/build2/variable
+++ b/build2/variable
@@ -372,6 +372,13 @@ namespace build2
   //   //
   //   static int compare (const T&, const T&);
   //
+  //   // For simple types (those that can be used as elements of containers),
+  //   // type_name must be constexpr in order to sidestep the static init
+  //   // order issue (in fact, that's the only reason we have it both here
+  //   // and in value_type.name -- value_type cannot be constexpr because
+  //   // of pointers to function template instantiations).
+  //   //
+  //   static const char* const type_name;
   //   static const build2::value_type value_type;
   // };
 
@@ -446,6 +453,7 @@ namespace build2
     static name reverse (bool x) {return name (x ? "true" : "false");}
     static int compare (bool, bool);
 
+    static const char* const type_name;
     static const build2::value_type value_type;
   };
 
@@ -460,6 +468,7 @@ namespace build2
     static name reverse (uint64_t x) {return name (to_string (x));}
     static int compare (uint64_t, uint64_t);
 
+    static const char* const type_name;
     static const build2::value_type value_type;
   };
 
@@ -477,6 +486,7 @@ namespace build2
     static name reverse (const string& x) {return name (x);}
     static int compare (const string&, const string&);
 
+    static const char* const type_name;
     static const build2::value_type value_type;
   };
 
@@ -494,6 +504,7 @@ namespace build2
     static name reverse (const path& x) {return name (x.string ());}
     static int compare (const path&, const path&);
 
+    static const char* const type_name;
     static const build2::value_type value_type;
   };
 
@@ -511,6 +522,7 @@ namespace build2
     static name reverse (const dir_path& x) {return name (x);}
     static int compare (const dir_path&, const dir_path&);
 
+    static const char* const type_name;
     static const build2::value_type value_type;
   };
 
@@ -528,6 +540,7 @@ namespace build2
     static name reverse (const abs_dir_path& x) {return name (x);}
     static int compare (const abs_dir_path&, const abs_dir_path&);
 
+    static const char* const type_name;
     static const build2::value_type value_type;
   };
 
@@ -545,6 +558,7 @@ namespace build2
     static name reverse (const name& x) {return x;}
     static int compare (const name&, const name&);
 
+    static const char* const type_name;
     static const build2::value_type value_type;
   };
 
diff --git a/build2/variable.cxx b/build2/variable.cxx
index 17a9d52..65bc023 100644
--- a/build2/variable.cxx
+++ b/build2/variable.cxx
@@ -333,9 +333,11 @@ namespace build2
     throw invalid_argument (string ());
   }
 
+  constexpr const char* const value_traits<bool>::type_name = "bool";
+
   const value_type value_traits<bool>::value_type
   {
-    "bool",
+    type_name,
     sizeof (bool),
     nullptr,                      // No base.
     nullptr,                      // No dtor (POD).
@@ -371,9 +373,11 @@ namespace build2
     throw invalid_argument (string ());
   }
 
+  constexpr const char* const value_traits<uint64_t>::type_name = "uint64";
+
   const value_type value_traits<uint64_t>::value_type
   {
-    "uint64",
+    type_name,
     sizeof (uint64_t),
     nullptr,                          // No base.
     nullptr,                          // No dtor (POD).
@@ -455,9 +459,11 @@ namespace build2
     return s;
   }
 
+  constexpr const char* const value_traits<string>::type_name = "string";
+
   const value_type value_traits<string>::value_type
   {
-    "string",
+    type_name,
     sizeof (string),
     nullptr,                      // No base.
     &default_dtor<string>,
@@ -498,9 +504,11 @@ namespace build2
     throw invalid_argument (string ());
   }
 
+  constexpr const char* const value_traits<path>::type_name = "path";
+
   const value_type value_traits<path>::value_type
   {
-    "path",
+    type_name,
     sizeof (path),
     nullptr,                    // No base.
     &default_dtor<path>,
@@ -539,9 +547,11 @@ namespace build2
     throw invalid_argument (string ());
   }
 
+  constexpr const char* const value_traits<dir_path>::type_name = "dir_path";
+
   const value_type value_traits<dir_path>::value_type
   {
-    "dir_path",
+    type_name,
     sizeof (dir_path),
     nullptr,                        // No base, or should it be path?
     &default_dtor<dir_path>,
@@ -570,9 +580,12 @@ namespace build2
     return abs_dir_path (move (d));
   }
 
+  constexpr const char* const value_traits<abs_dir_path>::type_name =
+    "abs_dir_path";
+
   const value_type value_traits<abs_dir_path>::value_type
   {
-    "abs_dir_path",
+    type_name,
     sizeof (abs_dir_path),
     &value_traits<dir_path>::value_type, // Assume direct cast works for both.
     &default_dtor<abs_dir_path>,
@@ -603,9 +616,11 @@ namespace build2
     return names_view (&v.as<name> (), 1);
   }
 
+  constexpr const char* const value_traits<name>::type_name = "name";
+
   const value_type value_traits<name>::value_type
   {
-    "name",
+    type_name,
     sizeof (name),
     nullptr,                    // No base.
     &default_dtor<name>,
diff --git a/build2/variable.txx b/build2/variable.txx
index 31d9284..6d3121a 100644
--- a/build2/variable.txx
+++ b/build2/variable.txx
@@ -272,7 +272,7 @@ namespace build2
 
   template <typename T>
   const string value_traits<vector<T>>::type_name = string (
-    value_traits<T>::value_type.name) + 's';
+    value_traits<T>::type_name) + 's';
 
   template <typename T>
   const value_type value_traits<vector<T>>::value_type
@@ -432,8 +432,8 @@ namespace build2
 
   template <typename K, typename V>
   const string value_traits<std::map<K, V>>::type_name = string (
-    value_traits<K>::value_type.name) + '_' +
-    value_traits<V>::value_type.name + "_map";
+    value_traits<K>::type_name) + '_' +
+    value_traits<V>::type_name + "_map";
 
   template <typename K, typename V>
   const value_type value_traits<std::map<K, V>>::value_type