lua.c

/*
** $Id: lua.c,v 1.234 2018/03/06 20:30:17 roberto Exp roberto $
** Lua stand-alone interpreter
** See Copyright Notice in lua.h
*/

#define lua_c

#include "lprefix.h"


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <signal.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"


#if !defined(LUA_PROGNAME)
#define LUA_PROGNAME		"lua"
#endif

#if !defined(LUA_INIT_VAR)
#define LUA_INIT_VAR		"LUA_INIT"
#endif

#define LUA_INITVARVERSION	LUA_INIT_VAR LUA_VERSUFFIX


static lua_State *globalL = NULL;

static const char *progname = LUA_PROGNAME;


/*
** Hook set by signal function to stop the interpreter.
*/
static void lstop (lua_State *L, lua_Debug *ar) {
 (void)ar; /* unused arg. */
 lua_sethook(L, NULL, 0, 0); /* reset hook */
 luaL_error(L, "interrupted!");
}


/*
** Function to be called at a C signal. Because a C signal cannot
** just change a Lua state (as there is no proper synchronization),
** this function only sets a hook that, when called, will stop the
** interpreter.
*/
static void laction (int i) {
 signal(i, SIG_DFL); /* if another SIGINT happens, terminate process */
 lua_sethook(globalL, lstop, LUA_MASKCALL | LUA_MASKRET | LUA_MASKCOUNT, 1);
}


static void print_usage (const char *badoption) {
 lua_writestringerror("%s: ", progname);
 if (badoption[1] == 'e' || badoption[1] == 'l')
 lua_writestringerror("'%s' needs argument\n", badoption);
 else
 lua_writestringerror("unrecognized option '%s'\n", badoption);
 lua_writestringerror(
 "usage: %s [options] [script [args]]\n"
 "Available options are:\n"
 " -e stat execute string 'stat'\n"
 " -i enter interactive mode after executing 'script'\n"
 " -l name require library 'name' into global 'name'\n"
 " -v show version information\n"
 " -E ignore environment variables\n"
 " -- stop handling options\n"
 " - stop handling options and execute stdin\n"
 ,
 progname);
}


/*
** Prints an error message, adding the program name in front of it
** (if present)
*/
static void l_message (const char *pname, const char *msg) {
 if (pname) lua_writestringerror("%s: ", pname);
 lua_writestringerror("%s\n", msg);
}


/*
** Check whether 'status' is not OK and, if so, prints the error
** message on the top of the stack. It assumes that the error object
** is a string, as it was either generated by Lua or by 'msghandler'.
*/
static int report (lua_State *L, int status) {
 if (status != LUA_OK) {
 const char *msg = lua_tostring(L, -1);
 l_message(progname, msg);
 lua_pop(L, 1); /* remove message */
 }
 return status;
}


/*
** Message handler used to run all chunks
*/
static int msghandler (lua_State *L) {
 const char *msg = lua_tostring(L, 1);
 if (msg == NULL) { /* is error object not a string? */
 if (luaL_callmeta(L, 1, "__tostring") && /* does it have a metamethod */
 lua_type(L, -1) == LUA_TSTRING) /* that produces a string? */
 return 1; /* that is the message */
 else
 msg = lua_pushfstring(L, "(error object is a %s value)",
 luaL_typename(L, 1));
 }
 luaL_traceback(L, L, msg, 1); /* append a standard traceback */
 return 1; /* return the traceback */
}


/*
** Interface to 'lua_pcall', which sets appropriate message function
** and C-signal handler. Used to run all chunks.
*/
static int docall (lua_State *L, int narg, int nres) {
 int status;
 int base = lua_gettop(L) - narg; /* function index */
 lua_pushcfunction(L, msghandler); /* push message handler */
 lua_insert(L, base); /* put it under function and args */
 globalL = L; /* to be available to 'laction' */
 signal(SIGINT, laction); /* set C-signal handler */
 status = lua_pcall(L, narg, nres, base);
 signal(SIGINT, SIG_DFL); /* reset C-signal handler */
 lua_remove(L, base); /* remove message handler from the stack */
 return status;
}


static void print_version (void) {
 lua_writestring(LUA_COPYRIGHT, strlen(LUA_COPYRIGHT));
 lua_writeline();
}


/*
** Create the 'arg' table, which stores all arguments from the
** command line ('argv'). It should be aligned so that, at index 0,
** it has 'argv[script]', which is the script name. The arguments
** to the script (everything after 'script') go to positive indices;
** other arguments (before the script name) go to negative indices.
** If there is no script name, assume interpreter's name as base.
*/
static void createargtable (lua_State *L, char **argv, int argc, int script) {
 int i, narg;
 if (script == argc) script = 0; /* no script name? */
 narg = argc - (script + 1); /* number of positive indices */
 lua_createtable(L, narg, script + 1);
 for (i = 0; i < argc; i++) {
 lua_pushstring(L, argv[i]);
 lua_rawseti(L, -2, i - script);
 }
 lua_setglobal(L, "arg");
}


static int dochunk (lua_State *L, int status) {
 if (status == LUA_OK) status = docall(L, 0, 0);
 return report(L, status);
}


static int dofile (lua_State *L, const char *name) {
 return dochunk(L, luaL_loadfile(L, name));
}


static int dostring (lua_State *L, const char *s, const char *name) {
 return dochunk(L, luaL_loadbuffer(L, s, strlen(s), name));
}


/*
** Calls 'require(name)' and stores the result in a global variable
** with the given name.
*/
static int dolibrary (lua_State *L, const char *name) {
 int status;
 lua_getglobal(L, "require");
 lua_pushstring(L, name);
 status = docall(L, 1, 1); /* call 'require(name)' */
 if (status == LUA_OK)
 lua_setglobal(L, name); /* global[name] = require return */
 return report(L, status);
}


/*
** Push on the stack the contents of table 'arg' from 1 to #arg
*/
static int pushargs (lua_State *L) {
 int i, n;
 if (lua_getglobal(L, "arg") != LUA_TTABLE)
 luaL_error(L, "'arg' is not a table");
 n = (int)luaL_len(L, -1);
 luaL_checkstack(L, n + 3, "too many arguments to script");
 for (i = 1; i <= n; i++)
 lua_rawgeti(L, -i, i);
 lua_remove(L, -i); /* remove table from the stack */
 return n;
}


static int handle_script (lua_State *L, char **argv) {
 int status;
 const char *fname = argv[0];
 if (strcmp(fname, "-") == 0 && strcmp(argv[-1], "--") != 0)
 fname = NULL; /* stdin */
 status = luaL_loadfile(L, fname);
 if (status == LUA_OK) {
 int n = pushargs(L); /* push arguments to script */
 status = docall(L, n, LUA_MULTRET);
 }
 return report(L, status);
}


/* bits of various argument indicators in 'args' */
#define has_error	1	/* bad option */
#define has_i		2	/* -i */
#define has_v		4	/* -v */
#define has_e		8	/* -e */
#define has_E		16	/* -E */


/*
** Traverses all arguments from 'argv', returning a mask with those
** needed before running any Lua code (or an error code if it finds
** any invalid argument). 'first' returns the first not-handled argument
** (either the script name or a bad argument in case of error).
*/
static int collectargs (char **argv, int *first) {
 int args = 0;
 int i;
 for (i = 1; argv[i] != NULL; i++) {
 *first = i;
 if (argv[i][0] != '-') /* not an option? */
 return args; /* stop handling options */
 switch (argv[i][1]) { /* else check option */
 case '-': /* '--' */
 if (argv[i][2] != '\0') /* extra characters after '--'? */
 return has_error; /* invalid option */
 *first = i + 1;
 return args;
 case '\0': /* '-' */
 return args; /* script "name" is '-' */
 case 'E':
 if (argv[i][2] != '\0') /* extra characters after 1st? */
 return has_error; /* invalid option */
 args |= has_E;
 break;
 case 'i':
 args |= has_i; /* (-i implies -v) *//* FALLTHROUGH */
 case 'v':
 if (argv[i][2] != '\0') /* extra characters after 1st? */
 return has_error; /* invalid option */
 args |= has_v;
 break;
 case 'e':
 args |= has_e; /* FALLTHROUGH */
 case 'l': /* both options need an argument */
 if (argv[i][2] == '\0') { /* no concatenated argument? */
 i++; /* try next 'argv' */
 if (argv[i] == NULL || argv[i][0] == '-')
 return has_error; /* no next argument or it is another option */
 }
 break;
 default: /* invalid option */
 return has_error;
 }
 }
 *first = i; /* no script name */
 return args;
}


/*
** Processes options 'e' and 'l', which involve running Lua code.
** Returns 0 if some code raises an error.
*/
static int runargs (lua_State *L, char **argv, int n) {
 int i;
 for (i = 1; i < n; i++) {
 int option = argv[i][1];
 lua_assert(argv[i][0] == '-'); /* already checked */
 if (option == 'e' || option == 'l') {
 int status;
 const char *extra = argv[i] + 2; /* both options need an argument */
 if (*extra == '\0') extra = argv[++i];
 lua_assert(extra != NULL);
 status = (option == 'e')
 ? dostring(L, extra, "=(command line)")
 : dolibrary(L, extra);
 if (status != LUA_OK) return 0;
 }
 }
 return 1;
}


static int handle_luainit (lua_State *L) {
 const char *name = "=" LUA_INITVARVERSION;
 const char *init = getenv(name + 1);
 if (init == NULL) {
 name = "=" LUA_INIT_VAR;
 init = getenv(name + 1); /* try alternative name */
 }
 if (init == NULL) return LUA_OK;
 else if (init[0] == '@')
 return dofile(L, init+1);
 else
 return dostring(L, init, name);
}


/*
** {==================================================================
** Read-Eval-Print Loop (REPL)
** ===================================================================
*/

#if !defined(LUA_PROMPT)
#define LUA_PROMPT		"> "
#define LUA_PROMPT2		">> "
#endif

#if !defined(LUA_MAXINPUT)
#define LUA_MAXINPUT		512
#endif


/*
** lua_stdin_is_tty detects whether the standard input is a 'tty' (that
** is, whether we're running lua interactively).
*/
#if !defined(lua_stdin_is_tty)	/* { */

#if defined(LUA_USE_POSIX)	/* { */

#include <unistd.h>
#define lua_stdin_is_tty()	isatty(0)

#elif defined(LUA_USE_WINDOWS)	/* }{ */

#include <io.h>
#include <windows.h>

#define lua_stdin_is_tty()	_isatty(_fileno(stdin))

#else				/* }{ */

/* ISO C definition */
#define lua_stdin_is_tty()	1 /* assume stdin is a tty */

#endif				/* } */

#endif				/* } */


/*
** lua_readline defines how to show a prompt and then read a line from
** the standard input.
** lua_saveline defines how to "save" a read line in a "history".
** lua_freeline defines how to free a line read by lua_readline.
*/
#if !defined(lua_readline)	/* { */

#if defined(LUA_USE_READLINE)	/* { */

#include <readline/readline.h>
#include <readline/history.h>
#define lua_initreadline(L) \
	((void)L, rl_readline_name="lua", rl_inhibit_completion=1)
#define lua_readline(L,b,p)	((void)L, ((b)=readline(p)) != NULL)
#define lua_saveline(L,line)	((void)L, add_history(line))
#define lua_freeline(L,b)	((void)L, free(b))

#else				/* }{ */

#define lua_initreadline(L) ((void)L)
#define lua_readline(L,b,p) \
 ((void)L, fputs(p, stdout), fflush(stdout), /* show prompt */ \
 fgets(b, LUA_MAXINPUT, stdin) != NULL) /* get line */
#define lua_saveline(L,line)	{ (void)L; (void)line; }
#define lua_freeline(L,b)	{ (void)L; (void)b; }

#endif				/* } */

#endif				/* } */


/*
** Returns the string to be used as a prompt by the interpreter.
*/
static const char *get_prompt (lua_State *L, int firstline) {
 const char *p;
 lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2");
 p = lua_tostring(L, -1);
 if (p == NULL) p = (firstline ? LUA_PROMPT : LUA_PROMPT2);
 return p;
}

/* mark in error messages for incomplete statements */
#define EOFMARK		"<eof>"
#define marklen		(sizeof(EOFMARK)/sizeof(char) - 1)


/*
** Check whether 'status' signals a syntax error and the error
** message at the top of the stack ends with the above mark for
** incomplete statements.
*/
static int incomplete (lua_State *L, int status) {
 if (status == LUA_ERRSYNTAX) {
 size_t lmsg;
 const char *msg = lua_tolstring(L, -1, &lmsg);
 if (lmsg >= marklen && strcmp(msg + lmsg - marklen, EOFMARK) == 0) {
 lua_pop(L, 1);
 return 1;
 }
 }
 return 0; /* else... */
}


/*
** Prompt the user, read a line, and push it into the Lua stack.
*/
static int pushline (lua_State *L, int firstline) {
 char buffer[LUA_MAXINPUT];
 char *b = buffer;
 size_t l;
 const char *prmt = get_prompt(L, firstline);
 int readstatus = lua_readline(L, b, prmt);
 if (readstatus == 0)
 return 0; /* no input (prompt will be popped by caller) */
 lua_pop(L, 1); /* remove prompt */
 l = strlen(b);
 if (l > 0 && b[l-1] == '\n') /* line ends with newline? */
 b[--l] = '\0'; /* remove it */
 if (firstline && b[0] == '=') /* for compatibility with 5.2, ... */
 lua_pushfstring(L, "return %s", b + 1); /* change '=' to 'return' */
 else
 lua_pushlstring(L, b, l);
 lua_freeline(L, b);
 return 1;
}


/*
** Try to compile line on the stack as 'return <line>;'; on return, stack
** has either compiled chunk or original line (if compilation failed).
*/
static int addreturn (lua_State *L) {
 const char *line = lua_tostring(L, -1); /* original line */
 const char *retline = lua_pushfstring(L, "return %s;", line);
 int status = luaL_loadbuffer(L, retline, strlen(retline), "=stdin");
 if (status == LUA_OK) {
 lua_remove(L, -2); /* remove modified line */
 if (line[0] != '\0') /* non empty? */
 lua_saveline(L, line); /* keep history */
 }
 else
 lua_pop(L, 2); /* pop result from 'luaL_loadbuffer' and modified line */
 return status;
}


/*
** Read multiple lines until a complete Lua statement
*/
static int multiline (lua_State *L) {
 for (;;) { /* repeat until gets a complete statement */
 size_t len;
 const char *line = lua_tolstring(L, 1, &len); /* get what it has */
 int status = luaL_loadbuffer(L, line, len, "=stdin"); /* try it */
 if (!incomplete(L, status) || !pushline(L, 0)) {
 lua_saveline(L, line); /* keep history */
 return status; /* cannot or should not try to add continuation line */
 }
 lua_pushliteral(L, "\n"); /* add newline... */
 lua_insert(L, -2); /* ...between the two lines */
 lua_concat(L, 3); /* join them */
 }
}


/*
** Read a line and try to load (compile) it first as an expression (by
** adding "return " in front of it) and second as a statement. Return
** the final status of load/call with the resulting function (if any)
** in the top of the stack.
*/
static int loadline (lua_State *L) {
 int status;
 lua_settop(L, 0);
 if (!pushline(L, 1))
 return -1; /* no input */
 if ((status = addreturn(L)) != LUA_OK) /* 'return ...' did not work? */
 status = multiline(L); /* try as command, maybe with continuation lines */
 lua_remove(L, 1); /* remove line from the stack */
 lua_assert(lua_gettop(L) == 1);
 return status;
}


/*
** Prints (calling the Lua 'print' function) any values on the stack
*/
static void l_print (lua_State *L) {
 int n = lua_gettop(L);
 if (n > 0) { /* any result to be printed? */
 luaL_checkstack(L, LUA_MINSTACK, "too many results to print");
 lua_getglobal(L, "print");
 lua_insert(L, 1);
 if (lua_pcall(L, n, 0, 0) != LUA_OK)
 l_message(progname, lua_pushfstring(L, "error calling 'print' (%s)",
 lua_tostring(L, -1)));
 }
}


/*
** Do the REPL: repeatedly read (load) a line, evaluate (call) it, and
** print any results.
*/
static void doREPL (lua_State *L) {
 int status;
 const char *oldprogname = progname;
 progname = NULL; /* no 'progname' on errors in interactive mode */
 lua_initreadline(L);
 while ((status = loadline(L)) != -1) {
 if (status == LUA_OK)
 status = docall(L, 0, LUA_MULTRET);
 if (status == LUA_OK) l_print(L);
 else report(L, status);
 }
 lua_settop(L, 0); /* clear stack */
 lua_writeline();
 progname = oldprogname;
}

/* }================================================================== */


/*
** Main body of stand-alone interpreter (to be called in protected mode).
** Reads the options and handles them all.
*/
static int pmain (lua_State *L) {
 int argc = (int)lua_tointeger(L, 1);
 char **argv = (char **)lua_touserdata(L, 2);
 int script;
 int args = collectargs(argv, &script);
 luaL_checkversion(L); /* check that interpreter has correct version */
 if (argv[0] && argv[0][0]) progname = argv[0];
 if (args == has_error) { /* bad arg? */
 print_usage(argv[script]); /* 'script' has index of bad arg. */
 return 0;
 }
 if (args & has_v) /* option '-v'? */
 print_version();
 if (args & has_E) { /* option '-E'? */
 lua_pushboolean(L, 1); /* signal for libraries to ignore env. vars. */
 lua_setfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
 }
 luaL_openlibs(L); /* open standard libraries */
 createargtable(L, argv, argc, script); /* create table 'arg' */
 lua_gc(L, LUA_GCGEN, 0, 0); /* GC in generational mode */
 if (!(args & has_E)) { /* no option '-E'? */
 if (handle_luainit(L) != LUA_OK) /* run LUA_INIT */
 return 0; /* error running LUA_INIT */
 }
 if (!runargs(L, argv, script)) /* execute arguments -e and -l */
 return 0; /* something failed */
 if (script < argc && /* execute main script (if there is one) */
 handle_script(L, argv + script) != LUA_OK)
 return 0;
 if (args & has_i) /* -i option? */
 doREPL(L); /* do read-eval-print loop */
 else if (script == argc && !(args & (has_e | has_v))) { /* no arguments? */
 if (lua_stdin_is_tty()) { /* running in interactive mode? */
 print_version();
 doREPL(L); /* do read-eval-print loop */
 }
 else dofile(L, NULL); /* executes stdin as a file */
 }
 lua_pushboolean(L, 1); /* signal no errors */
 return 1;
}


int main (int argc, char **argv) {
 int status, result;
 lua_State *L = luaL_newstate(); /* create state */
 if (L == NULL) {
 l_message(argv[0], "cannot create state: not enough memory");
 return EXIT_FAILURE;
 }
 lua_pushcfunction(L, &pmain); /* to call 'pmain' in protected mode */
 lua_pushinteger(L, argc); /* 1st argument */
 lua_pushlightuserdata(L, argv); /* 2nd argument */
 status = lua_pcall(L, 2, 1, 0); /* do the call */
 result = lua_toboolean(L, -1); /* get result */
 report(L, status);
 lua_close(L);
 return (result && status == LUA_OK) ? EXIT_SUCCESS : EXIT_FAILURE;
}