Dangerous string lifetime assumption

[snake-4]

luwra/lib/luwra/values.hpp

Line 211 in e0e4b6b

const char* ret = luaL_checkstring(state, -1);

The read method of Value specialization where type = const char* returns the result of a luaL_checklstring call and subsequently pops the string from the stack. The returned memory may unexpectedly be GC'd during another Lua operation.

This is contrary to the typical usage pattern of lua_tolstring where the returned memory would be used or copied before the value is popped.

luwra/lib/luwra/values.hpp

Line 230 in e0e4b6b

const char* value = luaL_checklstring(state, -1, &length);

The same problem exists to some degree in the type = std::string specialization, where the value is popped from the stack before a std::string is constructed using the pointer. In practice, the memory won't be GC'd in this instance but Lua makes no guarantee of this behavior and it may change in a future release.

I'd suggest either removing the const char* specialization or changing it so that it copies the string to a newly allocated location. The std::string specialization can be fixed by moving the construction of the std::string to before the pop call.