From 2f9e7be04bf493d6a5737c0782e4033fbc5261da Mon Sep 17 00:00:00 2001
From: Mike Armstrong <mikea@fb.com>
Date: Mon, 16 Nov 2015 09:33:59 -0800
Subject: [PATCH] fix output leaving bad characters in systrace output buffer
 due to overstepping bytes written

Differential Revision: D2658628

fb-gh-sync-id: e4c9dc66746177d371331d79972f1322239b4ea7
---
 ReactAndroid/src/main/jni/react/JSCTracing.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/ReactAndroid/src/main/jni/react/JSCTracing.cpp b/ReactAndroid/src/main/jni/react/JSCTracing.cpp
index 59affe892..fa786005e 100644
--- a/ReactAndroid/src/main/jni/react/JSCTracing.cpp
+++ b/ReactAndroid/src/main/jni/react/JSCTracing.cpp
@@ -42,6 +42,7 @@ static size_t copyTruncatedAsciiChars(
   // rather than the beginning.
   size_t toWrite = min(stringLen, min(bufLen, maxLen));
 
+  const char *startBuf = buf;
   const JSChar* chars = JSStringGetCharactersPtr(jsString);
   while (toWrite-- > 0) {
     *(buf++) = (char)*(chars++);
@@ -49,8 +50,8 @@ static size_t copyTruncatedAsciiChars(
 
   JSStringRelease(jsString);
 
-  // Return the full length to match snprintf semantics.
-  return stringLen;
+  // Return the number of bytes written
+  return buf - startBuf;
 }
 
 static size_t copyArgsToBuffer(