From 27fe185ed44b89a2c36b2036ec5f27da995e632f Mon Sep 17 00:00:00 2001
From: takase1121 <20792268+takase1121@users.noreply.github.com>
Date: Sat, 25 Sep 2021 10:31:15 +0800
Subject: [PATCH] fix unable to load any native library

something went wrong in snprintf that it skips the first character of
the library name. Not only that, the signature is actually luaopen and
not lua_open.
---
 src/api/system.c | 49 ++++++++++++++++++++++++------------------------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/src/api/system.c b/src/api/system.c
index 0cd64271..bcd1b997 100644
--- a/src/api/system.c
+++ b/src/api/system.c
@@ -695,39 +695,40 @@ static void* api_require(const char* symbol) {
   return NULL;
 }
 
-static int f_load_native_plugin(lua_State* L) {
-  size_t sname, namelen, pathlen;
-  int results;
-  char olib[512]; olib[sizeof(olib)-1] = 0;
-  const char* name = luaL_checklstring(L, -2, &namelen);
-  const char* path = luaL_checklstring(L, -1, &pathlen);
-  void* library = SDL_LoadObject(path);
-  if (name == 0 || !library)
+static int f_load_native_plugin(lua_State *L) {
+  char entrypoint_name[512]; entrypoint_name[sizeof(entrypoint_name) - 1] = '\0';
+  int result;
+
+  const char *name = luaL_checkstring(L, 1);
+  const char *path = luaL_checkstring(L, 2);
+  void *library = SDL_LoadObject(path);
+  if (!library)
     return luaL_error(L, "Unable to load %s: %s", name, SDL_GetError());
+
   lua_getglobal(L, "package");
   lua_getfield(L, -1, "native_plugins");
   lua_pushlightuserdata(L, library);
   lua_setfield(L, -2, name);
   lua_pop(L, 1);
-  for (sname = namelen - 1; sname > 0 && name[sname] != '.'; --sname);
-  snprintf(olib, sizeof(olib), "lua_open_lite_xl_%s", &name[sname+1]); 
-  int (*ext_entrypoint)(lua_State* L, void*) = SDL_LoadFunction(library, olib);
+
+  const char *basename = strrchr(name, '.');
+  basename = !basename ? name : basename + 1;
+  snprintf(entrypoint_name, sizeof(entrypoint_name), "luaopen_lite_xl_%s", basename);
+  int (*ext_entrypoint) (lua_State *L, void*) = SDL_LoadFunction(library, entrypoint_name);
   if (!ext_entrypoint) {
-    snprintf(olib, sizeof(olib), "lua_open_%s", &name[sname+1]);
-    int (*entrypoint)(lua_State* L) = SDL_LoadFunction(library, olib);
-    if (!entrypoint) {
-      return luaL_error(L, "Unable to load %s: Can't find entrypoint. Requires a "
-        "function defined as int lua_open_lite_xl_%s(lua_State* L, void* XL)", 
-        name, &name[sname+1]);
-    }
-    results = entrypoint(L);
+    snprintf(entrypoint_name, sizeof(entrypoint_name), "luaopen_%s", basename);
+    int (*entrypoint)(lua_State *L) = SDL_LoadFunction(library, entrypoint_name);
+    if (!entrypoint)
+      return luaL_error(L, "Unable to load %s: Can't find %s(lua_State *L, void *XL)", name, entrypoint_name);
+    result = entrypoint(L);
   } else {
-    results = ext_entrypoint(L, api_require);
+    result = ext_entrypoint(L, api_require);
   }
-  if (!results)
-    return luaL_error(L, "Unable to load %s: Your entrypoint must return at "
-    " least one value.", name);
-  return results;
+
+  if (!result)
+    return luaL_error(L, "Unable to load %s: entrypoint must return a value", name);
+
+  return result;
 }