Fix out-of-bounds read in Stream::PutCStringAsRawHex8

[teemperor]

Summary

When I added the Stream unit test (r338488), the build bots failed due to an out-of-
bound reads when passing an empty string to the PutCStringAsRawHex8 method.
In r338491 I removed the test case to fix the bots.

This patch fixes this in PutCStringAsRawHex8 by always checking for the terminating
null character in the given string (instead of skipping it the first time). It also re-adds the
test case I removed.

[vsk]

Thanks, LGTM.

lldb/trunk/source/Utility/Stream.cpp

size_t Stream::PutBytesAsRawHex8(const void *s, size_t src_len,
 
   return bytes_written;
 }
 
 size_t Stream::PutCStringAsRawHex8(const char *s) {
   size_t bytes_written = 0;
   bool binary_is_set = m_flags.Test(eBinary);
   m_flags.Clear(eBinary);
-  do {
+  while(*s) {
     bytes_written += _PutHex8(*s, false);
     ++s;
-  } while (*s);
+  }
   if (binary_is_set)
     m_flags.Set(eBinary);
   return bytes_written;
 }

lldb/trunk/unittests/Utility/StreamTest.cpp

TEST_F(StreamTest, PutCharNull) {
   s.PutChar('\0');
   EXPECT_EQ(std::string("\0", 1), TakeValue());
 
   s.PutChar('a');
   EXPECT_EQ(std::string("a", 1), TakeValue());
 }
 
 TEST_F(StreamTest, PutCStringAsRawHex8) {
+  s.PutCStringAsRawHex8("");
+  EXPECT_EQ("", TakeValue());
+
   s.PutCStringAsRawHex8("foobar");
   EXPECT_EQ("666f6f626172", TakeValue());
 
   s.PutCStringAsRawHex8(" ");
   EXPECT_EQ("20", TakeValue());
 }
 
 TEST_F(StreamTest, PutHex8) {