From b02880593e281ce44661ce22e9391edfe921e47e Mon Sep 17 00:00:00 2001
From: luukvbaal <31730729+luukvbaal@users.noreply.github.com>
Date: Thu, 23 Mar 2023 12:58:50 +0100
Subject: [PATCH] build(win): export extern symbols for use in FFI #22756

Makes `extern` variables accessible through ffi on Windows.

Follow-up to https://github.com/neovim/neovim/pull/15999
---
 src/nvim/main.c                  | 7 ++++++-
 test/functional/lua/ffi_spec.lua | 9 +++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/nvim/main.c b/src/nvim/main.c
index ea5f511fc6..a16badc1a0 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -1,7 +1,12 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
-#define EXTERN
+// Make sure extern symbols are exported on Windows
+#ifdef WIN32
+# define EXTERN __declspec(dllexport)
+#else
+# define EXTERN
+#endif
 #include <assert.h>
 #include <limits.h>
 #include <msgpack/pack.h>
diff --git a/test/functional/lua/ffi_spec.lua b/test/functional/lua/ffi_spec.lua
index 18b13a8959..c492c1e765 100644
--- a/test/functional/lua/ffi_spec.lua
+++ b/test/functional/lua/ffi_spec.lua
@@ -63,5 +63,14 @@ describe('ffi.cdef', function()
         nil
       )
     ]=])
+
+    -- Check that extern symbols are exported and accessible
+    eq(true, exec_lua[[
+      local ffi = require('ffi')
+
+      ffi.cdef('uint64_t display_tick;')
+
+      return ffi.C.display_tick >= 0
+    ]])
   end)
 end)