fix interal compiler error when building with mingw

include/fmt/format-inl.h

@@ -1147,7 +1147,8 @@ int snprintf_float(T value, int precision, float_specs specs,
           "fuzz mode - avoid large allocation inside snprintf");
 #endif
     // Suppress the warning about a nonliteral format string.
-    auto snprintf_ptr = FMT_SNPRINTF;
+    // Cannot use auto becase of a bug in MinGW (#1532).
+    int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
     int result = precision >= 0
                      ? snprintf_ptr(begin, capacity, format, precision, value)
                      : snprintf_ptr(begin, capacity, format, value);

src/format.cc

@@ -19,7 +19,7 @@ int format_float(char* buf, std::size_t size, const char* format, int precision,
         "fuzz mode - avoid large allocation inside snprintf");
 #endif
   // Suppress the warning about nonliteral format string.
-  auto snprintf_ptr = FMT_SNPRINTF;
+  int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
   return precision < 0 ? snprintf_ptr(buf, size, format, value)
                        : snprintf_ptr(buf, size, format, precision, value);
 }