From a3ab36c80399f13e05ff2ff142df58fa9f3fd103 Mon Sep 17 00:00:00 2001
From: Alex Guteniev <gutenev@gmail.com>
Date: Tue, 23 Nov 2021 22:55:22 +0200
Subject: [PATCH] Formatting of function pointers, member function pointers,
 member object pointers... (#2610)

---
 include/fmt/core.h                     | 7 +++++--
 test/compile-error-test/CMakeLists.txt | 6 ++++++
 test/core-test.cc                      | 7 +++++++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index bb56da7f..e2abdece 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -1372,8 +1372,11 @@ template <typename Context> struct arg_mapper {
   // the C array overload.
   template <
       typename T,
-      FMT_ENABLE_IF(std::is_convertible<const T&, const void*>::value &&
-                    !std::is_convertible<const T&, const char_type*>::value)>
+      FMT_ENABLE_IF(
+          std::is_member_pointer<T>::value ||
+          std::is_function<typename std::remove_pointer<T>::type>::value ||
+          (std::is_convertible<const T&, const void*>::value &&
+           !std::is_convertible<const T&, const char_type*>::value))>
   FMT_CONSTEXPR auto map(const T&) -> unformattable_pointer {
     return {};
   }
diff --git a/test/compile-error-test/CMakeLists.txt b/test/compile-error-test/CMakeLists.txt
index 8202f279..44bbb1ab 100644
--- a/test/compile-error-test/CMakeLists.txt
+++ b/test/compile-error-test/CMakeLists.txt
@@ -67,6 +67,12 @@ expect_compile_error("
   fmt::format(\"{}\", S());
 ")
 
+# Formatting a function
+expect_compile_error("
+  void (*f)();
+  fmt::format(\"{}\", f);
+")
+
 # Make sure that compiler features detected in the header
 # match the features detected in CMake.
 if (SUPPORTS_USER_DEFINED_LITERALS)
diff --git a/test/core-test.cc b/test/core-test.cc
index da3bc0f9..4f39c7ab 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -770,6 +770,13 @@ TEST(core_test, is_formattable) {
   static_assert(!fmt::is_formattable<unsigned char*, wchar_t>::value, "");
   static_assert(!fmt::is_formattable<const signed char*, wchar_t>::value, "");
   static_assert(!fmt::is_formattable<const unsigned char*, wchar_t>::value, "");
+
+  static_assert(!fmt::is_formattable<void (*)()>::value, "");
+
+  struct s;
+
+  static_assert(!fmt::is_formattable<int(s::*)>::value, "");
+  static_assert(!fmt::is_formattable<int (s::*)()>::value, "");
 }
 
 TEST(core_test, format) { EXPECT_EQ(fmt::format("{}", 42), "42"); }