scons,sim: Eliminate the generated cxx_config/init.cc file.

This file populated the "cxx_config_directory" map from type names to
directory entry generating types. It used a comprehensive list of
includes of all SimObject headers, and a comprehensive list of the
generating types to fill everything in.

Instead, this change creates a new singleton helper class which, when
instantiated as a static member of a CxxConfigParams subclass, will
install a pointer to a CxxConfigDirectoryEntry to that map during global
object construction time.

Also, this change renames the map to cxxConfigDirectory which is in
compliance with the style guide, and puts it behind an accessor which
returns a static variable which is the actual map. This avoids any
problems that might come from global object construction order.

Change-Id: Iaa913fbe5af1b11d90ca618e29420eeb7cb0faed
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49455
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/cxx_config.cc

@@ -43,6 +43,11 @@ namespace gem5
 const std::string CxxConfigParams::invalidName = "<invalid>";
 
 /** Directory of all SimObject classes config details */
-std::map<std::string, CxxConfigDirectoryEntry *> cxx_config_directory;
+std::map<std::string, CxxConfigDirectoryEntry *> &
+cxxConfigDirectory()
+{
+    static std::map<std::string, CxxConfigDirectoryEntry *> dir;
+    return dir;
+}
 
 } // namespace gem5

src/sim/cxx_config.hh

@@ -119,6 +119,9 @@ class CxxConfigDirectoryEntry
     virtual ~CxxConfigDirectoryEntry() { }
 };
 
+/** Directory of all SimObject classes config details */
+std::map<std::string, CxxConfigDirectoryEntry *> &cxxConfigDirectory();
+
 /** Base for peer classes of SimObjectParams derived classes with parameter
  *  modifying member functions. C++ configuration will offer objects of
  *  these classes to SimObjects as params rather than SimObjectParams
@@ -128,6 +131,18 @@ class CxxConfigParams
   private:
     static const std::string invalidName;
 
+  protected:
+    struct AddToConfigDir
+    {
+        AddToConfigDir(const std::string &name, CxxConfigDirectoryEntry *entry)
+        {
+            auto it_success = cxxConfigDirectory().insert({name, entry});
+            panic_if(!it_success.second,
+                    "Failed to insert config directory entry %s (duplicate?).",
+                    name);
+        }
+    };
+
   public:
     /** Flags passable to setParam... to smooth over any parsing difference
      *  between different config files */
@@ -229,14 +244,6 @@ class CxxConfigFileBase
     virtual CxxConfigParams::Flags getFlags() const { return 0; }
 };
 
-/** Directory of all SimObject classes config details */
-extern std::map<std::string, CxxConfigDirectoryEntry *>
-    cxx_config_directory;
-
-/** Initialise cxx_config_directory.  This is defined in the
- *  auto-generated .../cxx_config/init.cc */
-void cxxConfigInit();
-
 } // namespace gem5
 
 #endif // __SIM_CXX_CONFIG_HH__

src/sim/cxx_manager.cc

@@ -65,14 +65,14 @@ CxxConfigManager::findObjectType(const std::string &object_name,
     if (!configFile.getParam(object_name, "type", object_type))
         throw Exception(object_name, "Sim object has no 'type' field");
 
-    if (cxx_config_directory.find(object_type) ==
-        cxx_config_directory.end())
+    if (cxxConfigDirectory().find(object_type) ==
+        cxxConfigDirectory().end())
     {
         throw Exception(object_name, csprintf(
             "No sim object type %s is available", object_type));
     }
 
-    const CxxConfigDirectoryEntry *entry = cxx_config_directory[object_type];
+    const CxxConfigDirectoryEntry *entry = cxxConfigDirectory()[object_type];
 
     return *entry;
 }