add support for better error message back

format.cc

@@ -411,10 +411,12 @@ void fmt::BasicFormatter<Char>::CheckSign(const Char *&s, const Arg &arg) {
 template <typename Char>
 void fmt::BasicFormatter<Char>::DoFormat() {
   const Char *start = format_;
+  const Char *original = format_; // capture the format string before it is reset
   format_ = 0;
   next_arg_index_ = 0;
   const Char *s = start;
   BasicWriter<Char> &writer = *writer_;
+  try {
     while (*s) {
       Char c = *s++;
       if (c != '{' && c != '}') continue;
@@ -652,6 +654,10 @@ void fmt::BasicFormatter<Char>::DoFormat() {
         break;
       }
     }  
+  } catch (const FormatError &e) {
+    // rethrow FormatError with the format string pointed to by start
+    throw BasicFormatError<Char>(e.what(), original);
+  }
   writer.buffer_.append(start, s);
 }
 
@@ -687,6 +693,18 @@ template void fmt::BasicFormatter<char>::CheckSign(
 
 template void fmt::BasicFormatter<char>::DoFormat();
 
+#ifdef FMT_FORMAT_STRING_IN_ERRORS
+std::string fmt::FormatErrorMessage(const std::string &message, const char *format) {
+    fmt::Writer w;    
+    w << "error: " << message << " while parsing format string " << format;
+    return w.str();
+}
+#else
+std::string fmt::FormatErrorMessage(const std::string &message, const char *format) {
+    return message;
+}
+#endif
+
 // Explicit instantiations for wchar_t.
 
 template void fmt::BasicWriter<wchar_t>::FormatDouble<double>(
@@ -719,3 +737,21 @@ template void fmt::BasicFormatter<wchar_t>::CheckSign(
     const wchar_t *&s, const Arg &arg);
 
 template void fmt::BasicFormatter<wchar_t>::DoFormat();
+
+#ifdef FMT_FORMAT_STRING_IN_ERRORS
+std::string fmt::FormatErrorMessage(const std::string &message, const wchar_t *format) {
+
+    int size = FMT_SNPRINTF(NULL, 0, "%ls", format);
+    char* buf = (char*)malloc(size+1);
+    FMT_SNPRINTF(buf, size+1, "%ls", format);
+    
+    fmt::Writer w;    
+    w << "error: " << message << " while parsing format string " << buf;
+    free(buf);
+    return w.str();
+}
+#else
+std::string fmt::FormatErrorMessage(const std::string &message, const wchar_t *format) {
+    return message;
+}
+#endif

format.h

@@ -315,6 +315,20 @@ class FormatError : public std::runtime_error {
   : std::runtime_error(message) {}
 };
 
+std::string FormatErrorMessage(const std::string &message, const char *format);
+std::string FormatErrorMessage(const std::string &message, const wchar_t *format);
+
+template <typename Char>
+class BasicFormatError : public std::runtime_error {
+private:
+    std::basic_string<Char> format_;
+public:
+    explicit BasicFormatError(const std::string &message, const Char *format)
+        : std::runtime_error(fmt::FormatErrorMessage(message, format)), format_(format){}
+    virtual ~BasicFormatError() throw() {}
+    const Char *format() const { return format_.c_str(); }
+};
+
 enum Alignment {
   ALIGN_DEFAULT, ALIGN_LEFT, ALIGN_RIGHT, ALIGN_CENTER, ALIGN_NUMERIC
 };
@@ -402,6 +416,11 @@ class IntFormatter : public SpecT {
  */
 IntFormatter<int, TypeSpec<'b'> > bin(int value);
 
+/**
+  Returns an integer formatter that formats the value in base 2.
+ */
+IntFormatter<int, TypeSpec<'B'> > binu(int value);
+
 /**
   Returns an integer formatter that formats the value in base 8.
  */
@@ -439,7 +458,9 @@ IntFormatter<int, AlignTypeSpec<TYPE_CODE> > pad(
 inline IntFormatter<TYPE, TypeSpec<'b'> > bin(TYPE value) { \
   return IntFormatter<TYPE, TypeSpec<'b'> >(value, TypeSpec<'b'>()); \
 } \
- \
+inline IntFormatter<TYPE, TypeSpec<'B'> > binu(TYPE value) { \
+  return IntFormatter<TYPE, TypeSpec<'B'> >(value, TypeSpec<'B'>()); \
+} \
 inline IntFormatter<TYPE, TypeSpec<'o'> > oct(TYPE value) { \
   return IntFormatter<TYPE, TypeSpec<'o'> >(value, TypeSpec<'o'>()); \
 } \