Allocate large enough buffer to make _ecvt_s happy. Swap the order of template...

Allocate large enough buffer to make _ecvt_s happy. Swap the order of template parameters in TempFormatter for convenience.

format.h

@@ -191,8 +191,8 @@ inline int SignBit(double value) {
   if (value < 0) return 1;
   if (value == value) return 0;
   int dec = 0, sign = 0;
-  char dummy;
-  _ecvt_s(&dummy, 1, value, 0, &dec, &sign);
+  char buffer[2];  // The buffer size must be >= 2 or _ecvt_s will fail.
+  _ecvt_s(&buffer, sizeof(buffer), value, 0, &dec, &sign);
   return sign;
 }
 
@@ -1155,7 +1155,7 @@ class NoAction {
   Objects of this class normally exist only as temporaries returned
   by one of the formatting functions which explains the name.
  */
-template <typename Char, typename Action = NoAction>
+template <typename Action = NoAction, typename Char = char>
 class TempFormatter : public internal::ArgInserter<Char> {
  private:
   BasicFormatter<Char> formatter_;
@@ -1232,8 +1232,8 @@ class TempFormatter : public internal::ArgInserter<Char> {
   See also `Format String Syntax`_.
   \endrst
 */
-inline TempFormatter<char> Format(StringRef format) {
-  return TempFormatter<char>(format);
+inline TempFormatter<> Format(StringRef format) {
+  return TempFormatter<>(format);
 }
 
 // A formatting action that writes formatted output to stdout.
@@ -1246,8 +1246,8 @@ struct Write {
 // Formats a string and prints it to stdout.
 // Example:
 //   Print("Elapsed time: {0:.2f} seconds") << 1.23;
-inline TempFormatter<char, Write> Print(StringRef format) {
-  return TempFormatter<char, Write>(format);
+inline TempFormatter<Write> Print(StringRef format) {
+  return TempFormatter<Write>(format);
 }
 
 // Throws Exception(message) if format contains '}', otherwise throws

format_test.cc

@@ -1086,7 +1086,7 @@ struct CountCalls {
 TEST(TempFormatterTest, Action) {
   int num_calls = 0;
   {
-    fmt::TempFormatter<char, CountCalls> af("test", CountCalls(num_calls));
+    fmt::TempFormatter<CountCalls> af("test", CountCalls(num_calls));
     EXPECT_EQ(0, num_calls);
   }
   EXPECT_EQ(1, num_calls);
@@ -1095,7 +1095,7 @@ TEST(TempFormatterTest, Action) {
 TEST(TempFormatterTest, ActionNotCalledOnError) {
   int num_calls = 0;
   {
-    typedef fmt::TempFormatter<char, CountCalls> TestFormatter;
+    typedef fmt::TempFormatter<CountCalls> TestFormatter;
     EXPECT_THROW(TestFormatter af("{0", CountCalls(num_calls)), FormatError);
   }
   EXPECT_EQ(0, num_calls);
@@ -1108,8 +1108,8 @@ TEST(TempFormatterTest, ActionNotCalledOnError) {
 TEST(TempFormatterTest, ArgLifetime) {
   // The following code is for testing purposes only. It is a definite abuse
   // of the API and shouldn't be used in real applications.
-  const fmt::TempFormatter<char> &af = fmt::Format("{0}");
-  const_cast<fmt::TempFormatter<char>&>(af) << std::string("test");
+  const fmt::TempFormatter<> &af = fmt::Format("{0}");
+  const_cast<fmt::TempFormatter<>&>(af) << std::string("test");
   // String object passed as an argument to TempFormatter has
   // been destroyed, but ArgInserter dtor hasn't been called yet.
   // But that's OK since the Arg's dtor takes care of this and
@@ -1128,8 +1128,8 @@ struct PrintError {
   }
 };
 
-fmt::TempFormatter<char, PrintError> ReportError(const char *format) {
-  return fmt::TempFormatter<char, PrintError>(format);
+fmt::TempFormatter<PrintError> ReportError(const char *format) {
+  return fmt::TempFormatter<PrintError>(format);
 }
 
 TEST(TempFormatterTest, Examples) {