From Lua using debug.getinfo, e.g.,
local line = debug.getinfo(1).currentline
From C using lua_getinfo (This will return the linenumber inside lua code)
lua_Debug ar;
lua_getstack(L, 1, &ar);
lua_getinfo(L, "nSl", &ar);
int line = ar.currentline
http://www.lua.org/manual/5.1/manual.html#lua_getinfo
http://www.lua.org/manual/5.1/manual.html#pdf-debug.getinfo