From 81434980dc94c9d24ccbe386b6dddbbd9c99c3a7 Mon Sep 17 00:00:00 2001
From: Justin Riddell <arghnews@hotmail.co.uk>
Date: Tue, 27 Aug 2024 23:45:12 +0100
Subject: [PATCH] Fix gcc 8.1 - 8.3 bug and compilation

Fixes issue #4129
---
 include/fmt/base.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/fmt/base.h b/include/fmt/base.h
index 671c2ec7ec5f7..b99dfd7f5d991 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -1580,8 +1580,19 @@ template <> struct is_output_iterator<appender, char> : std::true_type {};
 
 template <typename It, typename T>
 struct is_output_iterator<
+#if FMT_GCC_VERSION >= 800 && FMT_GCC_VERSION <= 803
+    // Workaround old gcc bug, raised in issue 4129
+    It, T,
+    void_t<decltype(*std::declval<conditional_t<
+                        std::is_array<It>::value,
+                        typename std::add_pointer<
+                            typename std::remove_extent<It>::type>::type,
+                        It>&>()++ = std::declval<T>())>>
+#else
     It, T, void_t<decltype(*std::declval<It&>()++ = std::declval<T>())>>
-    : std::true_type {};
+#endif
+    : std::true_type {
+};
 
 // A type-erased reference to an std::locale to avoid a heavy <locale> include.
 class locale_ref {