Simplify RegisterBuiltinBuilder

Author: edolstra

src/libstore/include/nix/store/builtins.hh

@@ -19,12 +19,15 @@ using BuiltinBuilder = std::function<void(const BuiltinBuilderContext &)>;
 struct RegisterBuiltinBuilder
 {
     typedef std::map<std::string, BuiltinBuilder> BuiltinBuilders;
-    static BuiltinBuilders * builtinBuilders;
+
+    static BuiltinBuilders & builtinBuilders() {
+        static BuiltinBuilders builders;
+        return builders;
+    }
 
     RegisterBuiltinBuilder(const std::string & name, BuiltinBuilder && fun)
     {
-        if (!builtinBuilders) builtinBuilders = new BuiltinBuilders;
-        builtinBuilders->insert_or_assign(name, std::move(fun));
+        builtinBuilders().insert_or_assign(name, std::move(fun));
     }
 };
 

src/libstore/unix/build/derivation-builder.cc

@@ -1835,9 +1835,6 @@ void setupSeccomp()
 }
 
 
-RegisterBuiltinBuilder::BuiltinBuilders * RegisterBuiltinBuilder::builtinBuilders = nullptr;
-
-
 void DerivationBuilderImpl::runChild()
 {
     /* Warning: in the child we should absolutely not make any SQLite
@@ -2298,7 +2295,7 @@ void DerivationBuilderImpl::runChild()
 
                 std::string builtinName = drv.builder.substr(8);
                 assert(RegisterBuiltinBuilder::builtinBuilders);
-                if (auto builtin = get(*RegisterBuiltinBuilder::builtinBuilders, builtinName))
+                if (auto builtin = get(RegisterBuiltinBuilder::builtinBuilders(), builtinName))
                     (*builtin)(ctx);
                 else
                     throw Error("unsupported builtin builder '%1%'", builtinName);