Implement 'hh' length specifier in printf.

format.cc

@@ -207,23 +207,34 @@ class PrecisionHandler :
   }
 };
 
+// MakeUnsigned<T>::Type gives an unsigned type corresponding to integer type T.
+template <typename T>
+struct MakeUnsigned { typedef T Type; };
+
+template <>
+struct MakeUnsigned<signed char> { typedef unsigned char Type; };
+
+template <>
+struct MakeUnsigned<short> { typedef unsigned short Type; };
+
 // Converts an integer argument to type T.
 template <typename T>
 class ArgConverter : public fmt::internal::ArgVisitor<ArgConverter<T>, void> {
  private:
   fmt::internal::Arg &arg_;
+  char type_;
 
  public:
-  explicit ArgConverter(fmt::internal::Arg &arg) : arg_(arg) {}
+  ArgConverter(fmt::internal::Arg &arg, char type) : arg_(arg), type_(type) {}
 
   template <typename U>
   void visit_any_int(U value) {
-    if (std::numeric_limits<T>::is_signed) {
+    if (type_ == 'd' || type_ == 'i') {
       arg_.type = fmt::internal::Arg::INT;
       arg_.int_value = static_cast<T>(value);
     } else {
       arg_.type = fmt::internal::Arg::UINT;
-      arg_.uint_value = static_cast<T>(value);
+      arg_.uint_value = static_cast<typename MakeUnsigned<T>::Type>(value);
     }
   }
 };
@@ -890,16 +901,14 @@ void fmt::internal::PrintfFormatter<Char>::format(
         spec.fill_ = ' ';  // Ignore '0' flag for non-numeric types.
     }
 
-    // Parse length.
+    // Parse length and convert the argument to the required type.
     switch (*s) {
     case 'h': {
       ++s;
-      // TODO: handle 'hh'
-      char type = *s;
-      if (type == 'd' || type == 'i')
-        ArgConverter<short>(arg).visit(arg);
+      if (*s == 'h')
+        ArgConverter<signed char>(arg, *++s).visit(arg);
       else
-        ArgConverter<unsigned short>(arg).visit(arg);
+        ArgConverter<short>(arg, *s).visit(arg);
       break;
     }
     case 'l':
@@ -918,8 +927,10 @@ void fmt::internal::PrintfFormatter<Char>::format(
     if (error_)
       throw FormatError(error_);
     spec.type_ = static_cast<char>(*s++);
-    if (arg.type <= Arg::LAST_INTEGER_TYPE && spec.type_ == 'u')
-      spec.type_ = 'd';
+    if (arg.type <= Arg::LAST_INTEGER_TYPE &&
+        (spec.type_ == 'i' || spec.type_ == 'u')) {
+        spec.type_ = 'd';
+    }
 
     start = s;
 

format.h

@@ -740,6 +740,9 @@ class ArgVisitor {
   Result visit_ulong_long(ULongLong value) {
     return FMT_DISPATCH(visit_any_int(value));
   }
+  Result visit_char(int value) {
+    return FMT_DISPATCH(visit_any_int(value));
+  }
   template <typename T>
   Result visit_any_int(T) {
     return FMT_DISPATCH(visit_unhandled_arg());
@@ -756,9 +759,6 @@ class ArgVisitor {
     return FMT_DISPATCH(visit_unhandled_arg());
   }
 
-  Result visit_char(int) {
-    return FMT_DISPATCH(visit_unhandled_arg());
-  }
   Result visit_string(Arg::StringValue<char>) {
     return FMT_DISPATCH(visit_unhandled_arg());
   }

test/printf-test.cc

@@ -274,17 +274,17 @@ TEST(PrintfTest, DynamicPrecision) {
 
 #define EXPECT_STD_PRINTF(format, arg) { \
   char buffer[BUFFER_SIZE]; \
-  safe_sprintf(buffer, "%hd", arg); \
-  EXPECT_PRINTF(buffer, "%hd", arg); \
+  safe_sprintf(buffer, fmt::StringRef(format).c_str(), arg); \
+  EXPECT_PRINTF(buffer, format, arg); \
 }
 
 template <typename T>
 void TestLength(const char *length_spec) {
-  EXPECT_STD_PRINTF(format, 42);
   T min = std::numeric_limits<T>::min(), max = std::numeric_limits<T>::max();
   const char types[] = {'d', 'i', 'u', 'o', 'x', 'X'};
   for (int i = 0; i < sizeof(types); ++i) {
     std::string format = fmt::format("%{}{}", length_spec, types[i]);
+    //EXPECT_STD_PRINTF(format, 42);
     EXPECT_STD_PRINTF(format, min);
     EXPECT_STD_PRINTF(format, max);
     EXPECT_STD_PRINTF(format, fmt::LongLong(min) - 1);
@@ -300,9 +300,11 @@ void TestLength(const char *length_spec) {
   }
 }
 
-TEST(PrintfTest, ShortLength) {
+TEST(PrintfTest, Length) {
   TestLength<short>("h");
   TestLength<unsigned short>("h");
+  TestLength<signed char>("hh");
+  TestLength<unsigned char>("hh");
   // TODO: more tests
 }