From ac1a332ecf460120f7710ea8f9eeebd6ef84ed87 Mon Sep 17 00:00:00 2001
From: Kate <kit-ty-kate@outlook.com>
Date: Tue, 1 Oct 2024 15:40:12 +0100
Subject: [PATCH] Add a test-case showing a failure when -std=c++11 is not
 added to the C++ compiler arguments

Signed-off-by: Kate <kit-ty-kate@outlook.com>
---
 test/blackbox-tests/test-cases/cxx-flags.t/cpp11.cpp | 8 ++++++++
 test/blackbox-tests/test-cases/cxx-flags.t/cpp11.ml  | 3 +++
 test/blackbox-tests/test-cases/cxx-flags.t/dune      | 9 +++++++++
 test/blackbox-tests/test-cases/cxx-flags.t/run.t     | 8 ++++++++
 4 files changed, 28 insertions(+)
 create mode 100644 test/blackbox-tests/test-cases/cxx-flags.t/cpp11.cpp
 create mode 100644 test/blackbox-tests/test-cases/cxx-flags.t/cpp11.ml

diff --git a/test/blackbox-tests/test-cases/cxx-flags.t/cpp11.cpp b/test/blackbox-tests/test-cases/cxx-flags.t/cpp11.cpp
new file mode 100644
index 000000000000..7f3c6eec3fb0
--- /dev/null
+++ b/test/blackbox-tests/test-cases/cxx-flags.t/cpp11.cpp
@@ -0,0 +1,8 @@
+#include <caml/misc.h>
+#include <caml/mlvalues.h>
+#include <iostream>
+
+extern "C" CAMLprim value cpp11(value _unit) {
+  std::cout << "Hi from C++11" << std::endl;
+  return Val_unit;
+}
diff --git a/test/blackbox-tests/test-cases/cxx-flags.t/cpp11.ml b/test/blackbox-tests/test-cases/cxx-flags.t/cpp11.ml
new file mode 100644
index 000000000000..4d8f22206a22
--- /dev/null
+++ b/test/blackbox-tests/test-cases/cxx-flags.t/cpp11.ml
@@ -0,0 +1,3 @@
+external cpp11 : unit -> unit = "cpp11"
+
+let () = cpp11 ()
diff --git a/test/blackbox-tests/test-cases/cxx-flags.t/dune b/test/blackbox-tests/test-cases/cxx-flags.t/dune
index a3c46259b87e..f9b2d5643cee 100644
--- a/test/blackbox-tests/test-cases/cxx-flags.t/dune
+++ b/test/blackbox-tests/test-cases/cxx-flags.t/dune
@@ -31,3 +31,12 @@
    (= %{architecture} arm64)))
  (action
   (write-file extra_flags.sexp "(-ccopt -Wl,-no_warn_duplicate_libraries)")))
+
+; will fail if :standard doesn't have -std=c++11 on OCaml >= 5.0
+(executable
+ (name cpp11)
+ (modules cpp11)
+ (foreign_stubs
+  (language cxx)
+  (names cpp11)
+  (flags -std=c++98 :standard)))
diff --git a/test/blackbox-tests/test-cases/cxx-flags.t/run.t b/test/blackbox-tests/test-cases/cxx-flags.t/run.t
index 4e7b80b83432..3a2d24daa302 100644
--- a/test/blackbox-tests/test-cases/cxx-flags.t/run.t
+++ b/test/blackbox-tests/test-cases/cxx-flags.t/run.t
@@ -143,3 +143,11 @@ one can extend link flags in env
   $ dune rules sub/main.exe --profile some-profile  | tr -s '\n' ' ' |
   > grep -ce "Main.cmx$GCC_LF_LIB$OTHER\|Main.cmx$Clang_LF_LIB$OTHER\|Main.cmx$Msvc_LF_LIB$OTHER"
   1
+
+-std=c++11 is given on OCaml 5.0
+================================
+
+  $ dune clean
+
+  $ dune exec ./cpp11.exe
+  Hi from C++11