Make minetest abort on lua panic

Currently, lua does a regular exit() after a lua panic, which can make
a problem hard to debug. Invoking FATAL_ERROR() instead will print
some useful information, and abort() minetest, so that a debugger can
be used to analyze the situation.

src/script/cpp_api/s_base.cpp

@@ -40,6 +40,7 @@ extern "C" {
 
 #include <stdio.h>
 #include <cstdarg>
+#include <sstream>
 
 
 class ModNameStorer
@@ -77,6 +78,8 @@ ScriptApiBase::ScriptApiBase() :
 	m_luastack = luaL_newstate();
 	FATAL_ERROR_IF(!m_luastack, "luaL_newstate() failed");
 
+	lua_atpanic(m_luastack, &luaPanic);
+
 	luaL_openlibs(m_luastack);
 
 	// Make the ScriptApiBase* accessible to ModApiBase
@@ -120,6 +123,16 @@ ScriptApiBase::~ScriptApiBase()
 	lua_close(m_luastack);
 }
 
+int ScriptApiBase::luaPanic(lua_State *L)
+{
+	std::ostringstream oss;
+	oss << "LUA PANIC: unprotected error in call to Lua API ("
+		<< lua_tostring(L, -1) << ")";
+	FATAL_ERROR(oss.str().c_str());
+	// NOTREACHED
+	return 0;
+}
+
 void ScriptApiBase::loadMod(const std::string &script_path,
 		const std::string &mod_name)
 {

src/script/cpp_api/s_base.h

@@ -118,6 +118,8 @@ protected:
 #endif
 
 private:
+	static int luaPanic(lua_State *L);
+
 	lua_State*      m_luastack;
 
 	Server*         m_server;