lua script error checking

Question

Is it possible to check if a lua script contains errors without executing it? I have fallowing code:

    if(luaL_loadbuffer(L, data, size, name))
    {
             


        

Answer 1

(This was originally meant as a reply to the first comment to Krtek's question, but I ran out of space there and to be honest it works as an answer just fine.)

Functions are essentially values, and thus a named function is actually a variable of that name. Variables, by their very definition, can change as a script is executed. Hell, someone might accidentally redefine one of those functions. Is that bad? To sum my thoughts up: depending on the script, parameters passed and/or actual implementations of those pre-defined functions you speak of (one might unset itself or others, for example), it is not possible to guarantee things work unless you are willing to narrow down some of your demands. Lua is too dynamic for what you are looking for. :)

If you want a flawless test: create a dummy environment with all bells and whistles in place, and see if it crashes anywhere along the way (loading, executing, etc). This is basically a sort of unit test, and as such would be pretty heavy.

If you want a basic check to see if a script has a valid syntax: Krtek gave an answer for that already. I am quite sure (but not 100%) that the lua equivalent is to loadfile or loadstring, and the respective C equivalent is to try and lua_load() the code, each of which convert readable script to bytecode which you would already need to do before you could actually execute the code in your normal all-is-well usecase. (And if that contained function definitions, those would need to be executed later on for the code inside those to execute.)

However, these are the extent of your options with regards to pre-empting errors before they actually happen. Lua is a very dynamic language, and what is a great strength also makes for a weakness when you want to prove correctness. There are simply too many variables involved for a perfect solution.