From 63fe2d5bd20c9e90857c817870c541f36b2e814e Mon Sep 17 00:00:00 2001
From: Spiros Tsalikis <spiros.tsalikis@kitware.com>
Date: Thu, 22 Jul 2021 03:40:00 -0400
Subject: [PATCH] Add copy constructor for dynamic_format_arg_store, and test

---
 include/fmt/args.h | 12 ++++++++++++
 test/args-test.cc  | 13 +++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/fmt/args.h b/include/fmt/args.h
index 562e8ab1..36f62220 100644
--- a/include/fmt/args.h
+++ b/include/fmt/args.h
@@ -143,6 +143,18 @@ class dynamic_format_arg_store
   }
 
  public:
+  constexpr dynamic_format_arg_store() = default;
+
+  constexpr dynamic_format_arg_store(
+      const dynamic_format_arg_store<Context>& store)
+      :
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+        basic_format_args<Context>(),
+#endif
+        data_(store.data_),
+        named_info_(store.named_info_) {
+  }
+
   /**
     \rst
     Adds an argument into the dynamic store for later passing to a formatting
diff --git a/test/args-test.cc b/test/args-test.cc
index a7421bc5..2b1db8c8 100644
--- a/test/args-test.cc
+++ b/test/args-test.cc
@@ -171,3 +171,16 @@ TEST(args_test, throw_on_copy) {
   }
   EXPECT_EQ(fmt::vformat("{}", store), "foo");
 }
+
+TEST(args_test, copy_constructor) {
+  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  store.push_back(fmt::arg("test1", "value1"));
+  store.push_back(fmt::arg("test2", "value2"));
+  store.push_back(fmt::arg("test3", "value3"));
+
+  auto store2 = store;
+  store2.push_back(fmt::arg("test4", "value4"));
+
+  auto result = fmt::vformat("{test1} {test2} {test3} {test4}", store2);
+  EXPECT_EQ(result, "value1 value2 value3 value4");
+}