Stop overwriting errno in base::StringPrintf, StringAppendV, and StringToDouble

base/stringprintf_unittest.cc

Index: base/stringprintf_unittest.cc
diff --git a/base/stringprintf_unittest.cc b/base/stringprintf_unittest.cc
index 305d24a881fda67c28b478313d4477e519b78c8e..c04b17e4c7c0413a6f43f1bbfd29fec39512f6a6 100644
--- a/base/stringprintf_unittest.cc
+++ b/base/stringprintf_unittest.cc
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <errno.h>
+
 #include "base/basictypes.h"
 #include "base/stringprintf.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -172,4 +174,14 @@ TEST(StringPrintfTest, PositionalParameters) {
 #endif
 }
 
+// Test that StringPrintf and StringAppendV do not change errno.
+TEST(StringPrintfTest, StringPrintfErrno) {
+  errno = 1;
+  EXPECT_EQ("", StringPrintf("%s", ""));
+  EXPECT_EQ(1, errno);
+  std::string out;
+  StringAppendVTestHelper(&out, "%d foo %s", 1, "bar");
+  EXPECT_EQ(1, errno);
+}
+
 }  // namespace base