From e5c8a698637be0c2990a93b2954853fabf4ca1ce Mon Sep 17 00:00:00 2001
From: federico-busato <federico.busato@protonmail.com>
Date: Mon, 9 Dec 2019 17:50:56 +0100
Subject: [PATCH] Extend FMT_FALLTHROUGH compatibily to gcc and clang pre-C++17

---
 include/fmt/format.h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 01f41f5c..2e214da1 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -69,9 +69,17 @@
 #  define FMT_HAS_BUILTIN(x) 0
 #endif
 
-#if FMT_HAS_CPP_ATTRIBUTE(fallthrough) && \
-    (__cplusplus >= 201703 || FMT_GCC_VERSION != 0)
-#  define FMT_FALLTHROUGH [[fallthrough]]
+#if __cplusplus  == 201103L || __cplusplus  == 201402L
+#  if defined(__clang__)
+#    define FMT_FALLTHROUGH [[clang::fallthrough]];
+#  elif defined(__GNUC__) && __GNUC__ >= 7
+#    define FMT_FALLTHROUGH [[gnu::fallthrough]];
+#  else
+#    define FMT_FALLTHROUGH
+#  endif
+#elif FMT_HAS_CPP_ATTRIBUTE(fallthrough) && \
+     ((__cplusplus >= 201703) || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L))
+#  define FMT_FALLTHROUGH [[fallthrough]];
 #else
 #  define FMT_FALLTHROUGH
 #endif