commit 68cc06bafa6d74ad44c3c1ec0c1724a9f42cb456
author nharmata <nharmata@google.com> Thu Mar 01 10:21:57 2018 -0800
committer Copybara-Service <copybara-piper@google.com> Thu Mar 01 10:23:49 2018 -0800
tree 8b3570f3a450e7e19b950cbb230a62a7c7465725
parent 13aac65751e684d2a89e31be25543a6a0e9d2978

Make the distinction between "global frame" and "lexical frame" explicit. As a nice consequence, this lets us reduce GC churn since we no longer need to create a frame instance for the lexical frame at a callsite of either a function when the environment is frozen or a builtin function (since builtins cannot modify bindings in their lexical frame).

RELNOTES: None
PiperOrigin-RevId: 187495787

src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java b/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java
index aac54e0..f91d426 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java
@@ -20,6 +20,7 @@
 import com.google.devtools.build.lib.profiler.ProfilerTask;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.syntax.Environment.LexicalFrame;
 import com.google.devtools.build.lib.syntax.SkylarkType.SkylarkFunctionType;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -49,6 +50,10 @@
   public static final ExtraArgKind[] USE_AST_ENV =
       new ExtraArgKind[] {ExtraArgKind.SYNTAX_TREE, ExtraArgKind.ENVIRONMENT};
 
+  // Builtins cannot create or modify variable bindings. So it's sufficient to use a shared
+  // instance.
+  private static final LexicalFrame SHARED_LEXICAL_FRAME_FOR_BUILTIN_FUNCTION_CALLS =
+      LexicalFrame.create(Mutability.IMMUTABLE);
 
   // The underlying invoke() method.
   @Nullable private Method invokeMethod;
@@ -162,7 +167,7 @@
     Profiler.instance().startTask(ProfilerTask.SKYLARK_BUILTIN_FN, getName());
     // Last but not least, actually make an inner call to the function with the resolved arguments.
     try {
-      env.enterScope(this, ast, env.getGlobals());
+      env.enterScope(this, SHARED_LEXICAL_FRAME_FOR_BUILTIN_FUNCTION_CALLS, ast, env.getGlobals());
       return invokeMethod.invoke(this, args);
     } catch (InvocationTargetException x) {
       Throwable e = x.getCause();