Add support for int64_t in FormatInt.

format-test.cc

@@ -1411,6 +1411,9 @@ TEST(FormatterTest, Examples) {
 TEST(FormatIntTest, FormatInt) {
   EXPECT_EQ("42", fmt::FormatInt(42).str());
   EXPECT_EQ("-42", fmt::FormatInt(-42).str());
+  std::ostringstream os;
+  os << std::numeric_limits<int64_t>::max();
+  EXPECT_EQ(os.str(), fmt::FormatInt(std::numeric_limits<int64_t>::max()).str());
 }
 
 template <typename T>

format.h

@@ -1293,9 +1293,8 @@ class FormatInt {
     return buffer_end;
   }
   
- public:
-  explicit FormatInt(int value) {
-    unsigned abs_value = value;
+  void FormatSigned(int64_t value) {
+    uint64_t abs_value = value;
     bool negative = value < 0;
     if (negative)
       abs_value = 0 - value;
@@ -1303,6 +1302,10 @@ class FormatInt {
     if (negative)
       *--str_ = '-';
   }
+
+ public:
+  explicit FormatInt(int value) { FormatSigned(value); }
+  explicit FormatInt(int64_t value) { FormatSigned(value); }
   explicit FormatInt(unsigned value) : str_(FormatDecimal(value)) {}
   explicit FormatInt(uint64_t value) : str_(FormatDecimal(value)) {}