3 files changed, 58 insertions, 14 deletions

diff --git a/include/sb2.h b/include/sb2.h
index b0f1152..7dd2ee6 100644
--- a/include/sb2.h
+++ b/include/sb2.h
@@ -20,6 +20,15 @@ struct lua_instance {
 	int mapping_disabled;
 };
 
+/* This version string is used to check that the lua scripts offer 
+ * what the C files expect, and v.v.
+ * Increment the serial number (first number) and update the initials
+ * and date whenever the interface beween Lua and C is changed.
+ *
+ * NOTE: the corresponding identifier for Lua is in lua_scripts/main.lua
+*/
+#define SB2_LUA_C_INTERFACE_VERSION "28,lta-2008-09-23"
+
 void sb2_lua_init(void);
 struct lua_instance *get_lua(void);
 char *sb_decolonize_path(const char *path);
diff --git a/lua_scripts/main.lua b/lua_scripts/main.lua
index f71297a..9e141fe 100644
--- a/lua_scripts/main.lua
+++ b/lua_scripts/main.lua
@@ -8,6 +8,14 @@
 debug = os.getenv("SBOX_MAPPING_DEBUG")
 debug_messages_enabled = sb.debug_messages_enabled()
 
+-- This version string is used to check that the lua scripts offer 
+-- what the C files expect, and v.v.
+-- Increment the serial number (first number) and update the initials
+-- and date whenever the interface beween Lua and C is changed.
+--
+-- NOTE: the corresponding identifier for C is in include/sb2.h
+sb2_lua_c_interface_version = "28,lta-2008-09-23"
+
 function do_file(filename)
 	if (debug_messages_enabled) then
 		sb.log("debug", string.format("Loading '%s'", filename))
diff --git a/luaif/luaif.c b/luaif/luaif.c
index a48bb44..a4cfc16 100644
--- a/luaif/luaif.c
+++ b/luaif/luaif.c
@@ -106,6 +106,26 @@ static int lua_bind_sb_functions(lua_State *l);
 static pthread_key_t lua_key;
 static pthread_once_t lua_key_once = PTHREAD_ONCE_INIT;
 
+static char *read_string_variable_from_lua(
+	struct lua_instance *luaif,
+	const char *name)
+{
+	char *result = NULL;
+
+	if (luaif && name && *name) {
+		lua_getglobal(luaif->lua, name);
+		result = (char *)lua_tostring(luaif->lua, -1);
+		if (result) {
+			result = strdup(result);
+		}
+		SB_LOG(SB_LOGLEVEL_DEBUG,
+			"Lua variable %s = '%s', gettop=%d",
+			name, (result ? result : "<NULL>"),
+			lua_gettop(luaif->lua));
+	}
+	return(result);
+}
+
 static void free_lua(void *buf)
 {
 	free(buf);
@@ -132,6 +152,7 @@ static void alloc_lua(void)
 {
 	struct lua_instance *tmp;
 	char *main_lua_script = NULL;
+	char *lua_if_version = NULL;
 
 	check_pthread_library();
 
@@ -198,6 +219,25 @@ static void alloc_lua(void)
 	}
 	lua_call(tmp->lua, 0, 0);
 	enable_mapping(tmp);
+
+	/* check Lua/C interface version. */
+	lua_if_version = read_string_variable_from_lua(tmp,
+		"sb2_lua_c_interface_version");
+	if (!lua_if_version) {
+		SB_LOG(SB_LOGLEVEL_ERROR, "FATAL ERROR: "
+			"sb2's Lua scripts didn't provide"
+			" 'sb2_lua_c_interface_version' identifier!");
+		exit(1);
+	}
+	if (strcmp(lua_if_version, SB2_LUA_C_INTERFACE_VERSION)) {
+		SB_LOG(SB_LOGLEVEL_ERROR, "FATAL ERROR: "
+			"sb2's Lua script interface version mismatch:"
+			" scripts provide '%s', but '%s' was expected",
+			lua_if_version, SB2_LUA_C_INTERFACE_VERSION);
+		exit(1);
+	}
+	free(lua_if_version);
+
 	SB_LOG(SB_LOGLEVEL_DEBUG, "lua initialized.");
 	SB_LOG(SB_LOGLEVEL_NOISE, "gettop=%d", lua_gettop(tmp->lua));
 
@@ -261,22 +301,9 @@ void sb2_lua_init(void)
 char *sb2__read_string_variable_from_lua__(const char *name)
 {
 	struct lua_instance *luaif;
-	char *result = NULL;
 
 	luaif = get_lua();
-
-	if (luaif && name && *name) {
-		lua_getglobal(luaif->lua, name);
-		result = (char *)lua_tostring(luaif->lua, -1);
-		if (result) {
-			result = strdup(result);
-		}
-		SB_LOG(SB_LOGLEVEL_DEBUG,
-			"Lua variable %s = '%s', gettop=%d",
-			name, (result ? result : "<NULL>"),
-			lua_gettop(luaif->lua));
-	}
-	return(result);
+	return(read_string_variable_from_lua(luaif, name));
 }