From 25b143dd34fb587d1e35290c4b25bc08954800e2 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 7 Feb 2022 10:16:35 -0300
Subject: [PATCH] Bug: lua.c assumes that argv has at least one element

---
 lua.c | 35 +++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 12 deletions(-)

diff --git a/lua.c b/lua.c
index 0f1900444..7f7dc2b22 100644
--- a/src/lua.c
+++ b/src/lua.c
@@ -177,10 +177,11 @@ static void print_version (void) {
 ** 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.
+** (If there is no interpreter's name either, 'script' is -1, so
+** table sizes are zero.)
 */
 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++) {
@@ -268,14 +269,23 @@ static int handle_script (lua_State *L, char **argv) {
 
 /*
 ** 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).
+** needed before running any Lua code or an error code if it finds any
+** invalid argument. In case of error, 'first' is the index of the bad
+** argument.  Otherwise, 'first' is -1 if there is no program name,
+** 0 if there is no script name, or the index of the script name.
 */
 static int collectargs (char **argv, int *first) {
   int args = 0;
   int i;
-  for (i = 1; argv[i] != NULL; i++) {
+  if (argv[0] != NULL) {  /* is there a program name? */
+    if (argv[0][0])  /* not empty? */
+      progname = argv[0];  /* save it */
+  }
+  else {  /* no program name */
+    *first = -1;
+    return 0;
+  }
+  for (i = 1; argv[i] != NULL; i++) {  /* handle arguments */
     *first = i;
     if (argv[i][0] != '-')  /* not an option? */
         return args;  /* stop handling options */
@@ -316,7 +326,7 @@ static int collectargs (char **argv, int *first) {
         return has_error;
     }
   }
-  *first = i;  /* no script name */
+  *first = 0;  /* no script name */
   return args;
 }
 
@@ -609,8 +619,8 @@ static int pmain (lua_State *L) {
   char **argv = (char **)lua_touserdata(L, 2);
   int script;
   int args = collectargs(argv, &script);
+  int optlim = (script > 0) ? script : argc; /* first argv not an option */
   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;
@@ -628,14 +638,15 @@ static int pmain (lua_State *L) {
     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 */
+  if (!runargs(L, argv, optlim))  /* 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 (script > 0) {  /* execute main script (if there is one) */
+    if (handle_script(L, argv + script) != LUA_OK)
+      return 0;  /* interrupt in case of error */
+  }
   if (args & has_i)  /* -i option? */
     doREPL(L);  /* do read-eval-print loop */
-  else if (script == argc && !(args & (has_e | has_v))) {  /* no arguments? */
+  else if (script < 1 && !(args & (has_e | has_v))) { /* no active option? */
     if (lua_stdin_is_tty()) {  /* running in interactive mode? */
       print_version();
       doREPL(L);  /* do read-eval-print loop */