[Macros] Fix memory leak in expandMacroExpr

The result of `swift_ASTGen_lookupMacro` needs to be deallocated.

Author: rxwei

lib/Sema/TypeCheckMacros.cpp

@@ -107,7 +107,9 @@ StructDecl *MacroContextRequest::evaluate(Evaluator &evaluator,
     swift_ASTGen_getMacroEvaluationContext(
         (const void *)start, (void *)(DeclContext *)macroSourceFile,
         (void *)&ctx, builtinMacro, &context);
-    ctx.addCleanup([builtinMacro]() { swift_ASTGen_destroyMacro(builtinMacro); });
+    ctx.addCleanup([builtinMacro]() {
+      swift_ASTGen_destroyMacro(builtinMacro);
+    });
     return dyn_cast<StructDecl>((Decl *)context);
   } else {
     Parser parser(macroBufferID, *macroSourceFile, &ctx.Diags, nullptr,
@@ -145,7 +147,7 @@ Expr *swift::expandMacroExpr(
 
   // Built-in macros go through `MacroSystem` in Swift Syntax linked to this
   // compiler.
-  if (swift_ASTGen_lookupMacro(macroName.str().c_str())) {
+  if (auto *macro = swift_ASTGen_lookupMacro(macroName.str().c_str())) {
     auto astGenSourceFile = sourceFile->exportedSourceFile;
     if (!astGenSourceFile)
       return nullptr;
@@ -159,6 +161,7 @@ Expr *swift::expandMacroExpr(
       return nullptr;
     evaluatedSource = NullTerminatedStringRef(evaluatedSourceAddress,
                                               (size_t)evaluatedSourceLength);
+    free(macro);
   }
   // Other macros go through a compiler plugin.
   else {

test/Macros/macro_plugin_exec.swift

@@ -1,14 +1,17 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-build-swift -Xfrontend -disable-availability-checking -I%platform-module-dir/../.. -L%platform-dylib-dir/../.. -emit-library -emit-library-path=%t/%target-library-name(MacroDefinition) -working-directory=%t -module-name=MacroDefinition %S/Inputs/macro_definition.swift
 // RUN: %target-build-swift -L%platform-module-dir/../.. -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) %s -o %t/main
-// RUN: %target-run %t/main
+// RUN: %target-run %t/main | %FileCheck %s
 // REQUIRES: executable_test
 
 // FIXME: Swift parser is not enabled on Linux CI yet.
 // REQUIRES: OS=macosx
 
 print(#customStringify(3 + 2 - 1))
+// CHECK: (4, "3 + 2 - 1")
 
 print(#customStringify(1.0.truncatingRemainder(dividingBy: 1.0) + 3.0))
+// CHECK-NEXT: (3.0, "1.0.truncatingRemainder(dividingBy: 1.0) + 3.0")
 
 print(#customStringify(["a", "b", "c"] + ["d", "e", "f"]))
+// CHECK-NEXT: (["a", "b", "c", "d", "e", "f"], "[\"a\", \"b\", \"c\"] + [\"d\", \"e\", \"f\"]")