From 3304e1e517fb8aac008c4684e72a4b59b408414a Mon Sep 17 00:00:00 2001
From: Kahrl <kahrl@gmx.net>
Date: Tue, 25 Aug 2015 07:44:53 +0200
Subject: Push error handler afresh each time lua_pcall is used

Fixes "double fault" / "error in error handling" messages
(issue #1423) and instead shows a complete backtrace.
---
 src/script/cpp_api/s_base.cpp | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

(limited to 'src/script/cpp_api/s_base.cpp')

diff --git a/src/script/cpp_api/s_base.cpp b/src/script/cpp_api/s_base.cpp
index bfe03ec46..78b70e499 100644
--- a/src/script/cpp_api/s_base.cpp
+++ b/src/script/cpp_api/s_base.cpp
@@ -78,14 +78,14 @@ ScriptApiBase::ScriptApiBase()
 
 	luaL_openlibs(m_luastack);
 
-	// Add and save an error handler
-	lua_pushcfunction(m_luastack, script_error_handler);
-	m_errorhandler = lua_gettop(m_luastack);
-
 	// Make the ScriptApiBase* accessible to ModApiBase
 	lua_pushlightuserdata(m_luastack, this);
 	lua_rawseti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_SCRIPTAPI);
 
+	// Add and save an error handler
+	lua_pushcfunction(m_luastack, script_error_handler);
+	lua_rawseti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_ERROR_HANDLER);
+
 	// If we are using LuaJIT add a C++ wrapper function to catch
 	// exceptions thrown in Lua -> C++ calls
 #if USE_LUAJIT
@@ -133,13 +133,15 @@ bool ScriptApiBase::loadScript(const std::string &script_path, std::string *erro
 
 	lua_State *L = getStack();
 
+	int error_handler = PUSH_ERROR_HANDLER(L);
+
 	bool ok;
 	if (m_secure) {
 		ok = ScriptApiSecurity::safeLoadFile(L, script_path.c_str());
 	} else {
 		ok = !luaL_loadfile(L, script_path.c_str());
 	}
-	ok = ok && !lua_pcall(L, 0, 0, m_errorhandler);
+	ok = ok && !lua_pcall(L, 0, 0, error_handler);
 	if (!ok) {
 		std::string error_msg = lua_tostring(L, -1);
 		if (error)
@@ -150,9 +152,9 @@ bool ScriptApiBase::loadScript(const std::string &script_path, std::string *erro
 			<< error_msg << std::endl << std::endl
 			<< "======= END OF ERROR FROM LUA ========" << std::endl;
 		lua_pop(L, 1); // Pop error message from stack
-		return false;
 	}
-	return true;
+	lua_pop(L, 1); // Pop error handler
+	return ok;
 }
 
 // Push the list of callbacks (a lua table).
@@ -168,28 +170,28 @@ void ScriptApiBase::runCallbacksRaw(int nargs,
 	FATAL_ERROR_IF(lua_gettop(L) < nargs + 1, "Not enough arguments");
 
 	// Insert error handler
-	lua_pushcfunction(L, script_error_handler);
-	int errorhandler = lua_gettop(L) - nargs - 1;
-	lua_insert(L, errorhandler);
+	PUSH_ERROR_HANDLER(L);
+	int error_handler = lua_gettop(L) - nargs - 1;
+	lua_insert(L, error_handler);
 
 	// Insert run_callbacks between error handler and table
 	lua_getglobal(L, "core");
 	lua_getfield(L, -1, "run_callbacks");
 	lua_remove(L, -2);
-	lua_insert(L, errorhandler + 1);
+	lua_insert(L, error_handler + 1);
 
 	// Insert mode after table
 	lua_pushnumber(L, (int)mode);
-	lua_insert(L, errorhandler + 3);
+	lua_insert(L, error_handler + 3);
 
 	// Stack now looks like this:
 	// ... <error handler> <run_callbacks> <table> <mode> <arg#1> <arg#2> ... <arg#n>
 
-	int result = lua_pcall(L, nargs + 2, 1, errorhandler);
+	int result = lua_pcall(L, nargs + 2, 1, error_handler);
 	if (result != 0)
 		scriptError(result, fxn);
 
-	lua_remove(L, -2); // Remove error handler
+	lua_remove(L, error_handler);
 }
 
 void ScriptApiBase::realityCheck()
-- 
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