rocastocks rocastocks - 1 year ago 88
C Question

Syntax Change in lua 5.2 C api

I was trying to compile the example provided in the book Programming in Lua

But only works for lua 5.1, What are the steps to do it on 5.2?

This is the code I am using

#include <stdio.h>
#include <string.h>
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

int main (void) {
char buff[256];
int error;
lua_State *L = lua_open(); /* opens Lua */
while (fgets(buff, sizeof(buff), stdin) != NULL) {
error = luaL_loadbuffer(L, buff, strlen(buff), "line") ||
lua_pcall(L, 0, 0, 0);
if (error) {
fprintf(stderr, "%s", lua_tostring(L, -1));
lua_pop(L, 1); /* pop error message from the stack */
return 0;

After compiling with
gcc test01.c -I/usr/include/lua5.2 -L/usr/lib/x86_64-linux-gnu -llua5.2
I get the following errors:

test01.c: In function ‘main’:
test01.c:10:18: warning: initialization makes pointer from integer without a cas
t [enabled by default]
lua_State *L = lua_open(); /* opens Lua */
/tmp/ccyPRlV3.o: In function `main':
test01.c:(.text+0x21): undefined reference to `lua_open'
collect2: error: ld returned 1 exit status

Thank you in advance.

Answer Source

luaopen() is not used anymore, it's replaced by luaL_newstate, you can use luaL_newstate to create a state with a standard allocation function:

lua_State *L = luaL_newstate();    /* opens Lua */
luaL_openlibs(L);                  /* opens the standard libraries */

This API is changed since Lua 5.1

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