From d9096704dfa84aea94bb6ac2ffa02d88fa546bfa Mon Sep 17 00:00:00 2001
From: Alon Zakai <alonzakai@gmail.com>
Date: Fri, 22 Apr 2016 22:01:43 -0700
Subject: add an ArenaVector for internal array allocations in expression nodes

---
 src/ast_utils.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'src/ast_utils.h')

diff --git a/src/ast_utils.h b/src/ast_utils.h
index 66dbf039a..5b569435e 100644
--- a/src/ast_utils.h
+++ b/src/ast_utils.h
@@ -136,6 +136,16 @@ struct ExpressionManipulator {
   static void nop(InputType* target) {
     convert<InputType, Nop>(target);
   }
+
+  // Convert a node that allocates
+  template<typename InputType, typename OutputType>
+  static OutputType* convert(InputType *input, MixedArena& allocator) {
+    assert(sizeof(OutputType) <= sizeof(InputType));
+    input->~InputType(); // arena-allocaed, so no destructor, but avoid UB.
+    OutputType* output = (OutputType*)(input);
+    new (output) OutputType(allocator);
+    return output;
+  }
 };
 
 struct ExpressionAnalyzer {
-- 
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