[interpreter] Fix memory leak in Bytecodes::Decode().

src/interpreter/bytecodes.cc

Index: src/interpreter/bytecodes.cc
diff --git a/src/interpreter/bytecodes.cc b/src/interpreter/bytecodes.cc
index ac793dab6a60099e55295c611814c3978a6aab3a..136e2802be988c01590453ba4305a455e6d2cb8d 100644
--- a/src/interpreter/bytecodes.cc
+++ b/src/interpreter/bytecodes.cc
@@ -4,6 +4,8 @@
 
 #include "src/interpreter/bytecodes.h"
 
+#include <iomanip>
+
 #include "src/frames.h"
 #include "src/interpreter/bytecode-traits.h"
 
@@ -484,8 +486,6 @@ uint32_t Bytecodes::DecodeUnsignedOperand(const uint8_t* operand_start,
 // static
 std::ostream& Bytecodes::Decode(std::ostream& os, const uint8_t* bytecode_start,
                                 int parameter_count) {
-  Vector<char> buf = Vector<char>::New(50);
-
   Bytecode bytecode = Bytecodes::FromByte(bytecode_start[0]);
   int prefix_offset = 0;
   OperandScale operand_scale = OperandScale::kSingle;
@@ -494,11 +494,19 @@ std::ostream& Bytecodes::Decode(std::ostream& os, const uint8_t* bytecode_start,
     operand_scale = Bytecodes::PrefixBytecodeToOperandScale(bytecode);

[Michael Achenbach, 2016/03/24 13:35:29]

FYI: The experimental code-coverage claims this code isn't executed on x64. Is
that maybe the case or are we missing to run a test? In which scenario would
this code path get exercised?

I assumed it would get exercised through the test that is unskipped in this CL.
But I'm not seeing that test in the output of any test step of the coverage bot.
Is this test maybe skipped otherwise or reported under a different label? Or I
need to track down an infrastructure bug.

     bytecode = Bytecodes::FromByte(bytecode_start[1]);
   }
+
+  // Prepare to print bytecode and operands as hex digits.
+  std::ios saved_format(nullptr);
+  saved_format.copyfmt(saved_format);
+  os.fill('0');
+  os.flags(std::ios::hex);
+
   int bytecode_size = Bytecodes::Size(bytecode, operand_scale);
   for (int i = 0; i < prefix_offset + bytecode_size; i++) {
-    SNPrintF(buf, "%02x ", bytecode_start[i]);
-    os << buf.start();
+    os << std::setw(2) << static_cast<uint32_t>(bytecode_start[i]) << ' ';
   }
+  os.copyfmt(saved_format);
+
   const int kBytecodeColumnSize = 6;
   for (int i = prefix_offset + bytecode_size; i < kBytecodeColumnSize; i++) {
     os << "   ";