From 2a0c98cb7a950334758ce933d2737a4f455a8b3d Mon Sep 17 00:00:00 2001
From: Vladislav Shchapov <vladislav@shchapov.ru>
Date: Fri, 23 Dec 2022 17:47:54 +0500
Subject: [PATCH] Fix for issue #3241

Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>
---
 include/fmt/core.h  | 2 +-
 test/format-test.cc | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 968466c2..83c5f786 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -863,7 +863,7 @@ template <typename Char, typename T, typename U,
 FMT_CONSTEXPR auto copy_str(T* begin, T* end, U* out) -> U* {
   if (is_constant_evaluated()) return copy_str<Char, T*, U*>(begin, end, out);
   auto size = to_unsigned(end - begin);
-  memcpy(out, begin, size * sizeof(U));
+  if (size > 0) memcpy(out, begin, size * sizeof(U));
   return out + size;
 }
 
diff --git a/test/format-test.cc b/test/format-test.cc
index 69e2c4d6..b71355f3 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -2047,6 +2047,10 @@ TEST(format_test, to_string) {
 #if FMT_USE_FLOAT128
   EXPECT_EQ(fmt::to_string(__float128(0.5)), "0.5");
 #endif
+
+#if defined(FMT_USE_STRING_VIEW) && FMT_CPLUSPLUS >= 201703L
+  EXPECT_EQ(fmt::to_string(std::string_view()), "");
+#endif
 }
 
 TEST(format_test, output_iterators) {