And if you are a hard core C/C fan for embedded applications and coming with a background of early old days of 8085 and x86 assembly language programming,then reading through Lua language syntax reminds your old days of programming with Stacks, and the frequent Push and Pop calls. Embedding Lua in C #1 - Building Lua From Source. This is the CMakeLists.txt i used to build Lua as a static lib. I just quickly made it myself, you just need to make sure you don't try to build the standalone intepreter and compiler (luac.c & lua.c), as they have their own main methods in there.

2020-03-01 Using Lua with SDL 2 - Example

by Andre Leiradella

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Lua provides the luaL_requiref function to allow the embedding of modules, either native or written in Lua, into the executable instead of relying on the file system and search paths to locate and load modules into a Lua state.

Besides the Lua state, luaLrequiref needs the module name as a C string, and a lua_CFunction argument that is responsible for providing the module. Its signature is:

Tired: `luaLrequiref`

luaLrequiref works by checking if a module with the name passed in modname was already loaded and, if not, by calling the openf function and setting the module as the result of that call. It can also set a global variable with modname with the result of the call when glb is not zero:

To use luaL_requiref with modules written in Lua, an intermediary function to compile the Lua source code is needed. Since luaL_requiref passes modname to openf, it’s trivial to write such function:

This is all easy and works as intended, but introduces a dependency problem when many modules are embedded, as some modules may depend on other modules. The problem is that when a module is required via luaL_requiref, all the modules that it requires must be already known to the Lua state, otherwise require will fail to load the module.

The only way around this issue is calling luaL_requiref in a order that satisfies these dependencies, so that when a module is loaded, all modules that are dependencies of that module were already loaded.

Although the correct order of the luaL_requiref calls is not difficult to achieve, another problem with this approach is that all modules are forcibly loaded even though the Lua code ends up not requiring all of them.

Wired: register our own searcher

In Lua, a searcher is a function that is responsible for locating a module by its name and loading it. When created, a Lua state already comes with four searches defined by default.

It’s possible to add new searchers to the list and load modules in ways not supported by the default loaders. So instead of using luaL_requiref to pre-load all modules that we want to embed in the application, we can register a search that knows how to locate and load them.

The code below registers a searcher that can load any module from the LuaSocket library:

Now when someone requires any LuaSocket module, our searcher function will end up being called, and will return the function that defines the module. If that module in its turn requires another module, the searcher function will be called again and all the dependencies will be satisfied without requiring manual ordering of the dependencies.

Also, only the modules effectively used by the Lua code will be loaded into the Lua state.

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In this short tutorial I'll show how to run Lua programs from C and C++ and howto expose functions to them. It's easy!

Update: The code in this post has been updated for Lua 5.2.4. I haven'tchecked if the Lua 5.3 C API is backwards-compatible with 5.2. All the codehere is available on GitHub.

The first program will just create a Lua state object and exit. It will be ahybrid between C and C++. Since the two languages must include different files,we need to discern between them by checking for the existence of the__cplusplus macro.

Notice that I'm being explicit about which version of Lua I'm using in thecode. If you trust that the Lua developers care about compatibility, you canjust #include <lua.hpp> and so on directly.

The purpose of the program is just to make sure that we can compile, link andrun it without errors.

You need to let the compiler know where it can find the include files and theLua shared library. The include files are usually located in/usr/local/include and the library files in /usr/local/lib. Search yoursystem directories if needed. To compile the above program, pass thedirectories with -I and -L, respectively.

You may swap out g++ with llvm-g++, or just c++, depending on yourcompiler. If you're using a C compiler, use gcc or llvm-gcc — butremember to rename the file to first.c.

Now try to run the program to make sure it doesn't segfault:

This one worked just fine.

Embedding Lua In C · GitHub

Executing Lua programs from a host

The next step is to execute Lua programs from your C or C++ code. We'll createthe Lua state object as above, load a file from disk and execute it.

Embed Lua In C#

Put this into runlua.cpp or runlua.c:

You can reuse the compilation arguments from above:

Running Lua programs

How To Embed Lua In C++

Let's test this with some Lua programs. The first one prints the Lua versionand exits.

You may want to double-check that it works by running lua hello.lua. It maynot be important for this trivial program, but can become important when youtry more advanced ones.

Now try it with runlua:

You can even run bytecode-compiled programs:

Lua c api create table. In the lua-intf, LuaState and luaState. are inter-changeable, you can pick the coding style you like most.LuaState does not manage luaState.

We should also check that the error handling works. Put some garbage in a filecalled error.lua, for example

Running it produces

Calling C functions from Lua

It gets very interesting when Lua programs call back to your C or C++functions. We'll create a function called howdy that prints its inputarguments and returns the integer 123.

To be on the safe side, we'll declare C linkage for the function in the C++version of the program. This has to do with name mangling,but in this case, it really doesn't matter: Lua just receives a pointer to afunction, and that's that. But if you start using dynamic loading of sharedlibraries through dlopen and dlsym, this will be an issue. So let's do itcorrect from the start.

Copy the above program into a file called callback.cpp and add the howdyfunction.

We have to pass the address of this function to Lua along with a name. Put thefollowing line somewhere between the call to lua_newstate andluaL_loadfile:

Create a test program called callback.lua

Compile and test it

I told you it was easy!

What next?

Read the Lua C APIReference. You've learned enough now to get going with it. Did you see mynote about clearing the stack in howdy? You may want to investigate that.

Find out how to integrate Lua closures with your C functions.

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Tired: luaLrequiref