Fix ofstream handling in msvc

include/fmt/ostream.h

@@ -82,7 +82,9 @@ template class filebuf_access<filebuf_access_tag,
                               &filebuf_type::_Myfile>;
 
 inline bool write(std::filebuf& buf, fmt::string_view data) {
-  print(get_file(buf), data);
+  FILE* f = get_file(buf);
+  if (!f) return false;
+  print(f, data);
   return true;
 }
 inline bool write(std::wfilebuf&, fmt::basic_string_view<wchar_t>) {

test/ostream-test.cc

@@ -5,6 +5,8 @@
 //
 // For the license information refer to format.h.
 
+#include <fstream>
+
 #include "fmt/format.h"
 
 using fmt::runtime;
@@ -297,3 +299,8 @@ TEST(ostream_test, is_formattable) {
   EXPECT_TRUE(fmt::is_formattable<std::string>());
   EXPECT_TRUE(fmt::is_formattable<fmt::detail::std_string_view<char>>());
 }
+
+TEST(ostream_test, closed_ofstream) {
+  std::ofstream ofs;
+  fmt::print(ofs, "discard");
+}