Added in sample plugin and tested things out. Works.

build_plugin.sh

@@ -0,0 +1 @@
+gcc sample_plugin.c -shared -o data/plugins/sample.so

data/core/init.lua

@@ -426,6 +426,8 @@ function core.init()
   NagView = require "core.nagview"
   DocView = require "core.docview"
   Doc = require "core.doc"
+  local PluginTest = require "plugins.sample"
+  print(PluginTest.example)
 
   if PATHSEP == '\\' then
     USERDIR = common.normalize_path(USERDIR)
@@ -675,7 +677,6 @@ local function check_plugin_version(filename)
   return true, version_match
 end
 
-
 function core.load_plugins()
   local no_errors = true
   local refused_list = {

data/core/start.lua

@@ -19,4 +19,5 @@ package.path = DATADIR .. '/?.lua;' .. package.path
 package.path = DATADIR .. '/?/init.lua;' .. package.path
 package.path = USERDIR .. '/?.lua;' .. package.path
 package.path = USERDIR .. '/?/init.lua;' .. package.path
+package.cpath = DATADIR .. '/?.' .. (MACOS and 'lib' or (WINDOWS and 'dll' or 'so')) .. ';' .. package.cpath
 package.searchers[3] = system.searcher_plugin

sample_plugin.c

@@ -0,0 +1,14 @@
+
+typedef struct lua_State lua_State;
+#define SYMBOL(NAME, RTYPE, ...) RTYPE (*lua_##NAME)(lua_State*, __VA_ARGS__) = (RTYPE (*)(lua_State*, __VA_ARGS__))symbol("lua_" #NAME);
+
+int lua_open_sample(lua_State* L, void* (*symbol(const char*))) {
+  SYMBOL(createtable, void, int, int);
+  SYMBOL(setfield, void, int, const char*);
+  SYMBOL(pushstring, const char*, const char*);
+  
+  lua_createtable(L, 0, 0);
+  lua_pushstring(L, "value");
+  lua_setfield(L, -2, "example");
+  return 1;
+}

src/api/system.c

@@ -684,12 +684,12 @@ static int loader_plugin(lua_State* L) {
   if (modlen == 0 || !library)
     return luaL_error(L, "Unable to load %s: %s", modname, SDL_GetError());
   for (sname = modlen - 1; sname > 0 && modname[sname] != '.'; --sname);
-  strncat(buffer, &modname[sname], modlen - sname + 1);
+  strcat(buffer, &modname[sname+1]);
   int (*entrypoint)(lua_State* L, void*) = SDL_LoadFunction(library, buffer);
   if (!entrypoint) {
-    return luaL_error(L, "Unable to load %s: Can't find entrypoint. Requires a \
-      function defined as int %s(lua_State* L, void* (*symbol)(const char*))", 
-    path, buffer);
+    return luaL_error(L, "Unable to load %s: Can't find entrypoint. Requires a "
+      "function defined as int %s(lua_State* L, void* (*symbol)(const char*))", 
+    modname, buffer);
   }
   lua_pushlightuserdata(L, library);
   lua_setfield(L, LUA_REGISTRYINDEX, modname);
@@ -701,7 +701,13 @@ static int loader_plugin(lua_State* L) {
 
 #if _WIN32
   #define PATH_SEPARATOR '\\'
+  #define DYNAMIC_SUFFIX "dll"
 #else 
+  #if __APPLE__
+    #define DYNAMIC_SUFFIX "lib"
+  #else
+    #define DYNAMIC_SUFFIX "so"
+  #endif
   #define PATH_SEPARATOR '/'
 #endif
 static int f_searcher_plugin(lua_State *L) {
@@ -716,13 +722,14 @@ static int f_searcher_plugin(lua_State *L) {
       if (cpath_q) {
         size_t offset = cpath_q - cpath_idx;
         strncpy(lib, &cpath[cpath_idx], offset);
-        for (size_t j = 0; j < len && j < sizeof(lib) - 1; ++j)
+        for (size_t j = 0; j < len && j < sizeof(lib) - 3; ++j)
           lib[offset++] = modname[j] != '.' ? modname[j] : PATH_SEPARATOR;
         lib[offset++] = '\0';
+        strcat(lib, "." DYNAMIC_SUFFIX);
         struct stat s;
         if (!stat(lib, &s)) {
           lua_pushcfunction(L, loader_plugin);
-          lua_pushlstring(L, lib, offset);
+          lua_pushstring(L, lib);
           return 2;
         }
       }

src/main.c

@@ -139,13 +139,17 @@ init_lua:
   lua_pushstring(L, exename);
   lua_setglobal(L, "EXEFILE");
 
-#ifdef __APPLE__
   lua_pushboolean(L, true);
+#ifdef __APPLE__
   lua_setglobal(L, "MACOS");
   enable_momentum_scroll();
   #ifdef MACOS_USE_BUNDLE
     set_macos_bundle_resources(L);
   #endif
+#elsif _WIN32
+  lua_setglobal(L, "WINDOWS");
+#else
+  lua_setglobal(L, "LINUX");
 #endif
 
   const char *init_lite_code = \