SIGSEGV error in some lua/c++ code

Question

The following code end in a SIGSEGV error:

extern "C" {
    #include "lua/lua.h"
    #include "lua/lualib.h"
    #include "lua/lauxlib.h"
}

int main( int argc, char *argv[] )
{
    lua_State *L;
    luaL_openlibs(L);
    lua_close(L);
    return 0;
}

Gdb gives me the following:

(gdb) run
Starting program: d:\Dropbox\cpp\engine\bin\main.exe
[New Thread 7008.0x1df8]

Program received signal SIGSEGV, Segmentation fault.
0x6d781f30 in lua_pushcclosure () from d:\Dropbox\cpp\engine\bin\lua52.dll
(gdb) where
#0  0x6d781f30 in lua_pushcclosure () from d:\Dropbox\cpp\engine\bin\lua52.dll
#1  0x6d79329e in luaL_requiref () from d:\Dropbox\cpp\engine\bin\lua52.dll
#2  0x6d79bdee in luaL_openlibs () from d:\Dropbox\cpp\engine\bin\lua52.dll
#3  0x004013a6 in main (argc=1, argv=0x702fc8) at main.cpp:10
(gdb)

Answer 1

You have to do create a new lua state before opening the lib ( luaL_openlibs(L); ), like this:

L = luaL_newstate();

You get the segmentation fault because you have an unitialized pointer, dereferencing it (which is what the lib does) is undefined behavior.