hush: fix "getopts" builtin to not be upset by other builtins calling getopt()

function                                             old     new   delta
builtin_getopts                                      363     403     +40
unset_local_var_len                                  185     215     +30
set_local_var                                        440     466     +26
reset_traps_to_defaults                              151     157      +6
pseudo_exec_argv                                     320     326      +6
install_special_sighandlers                           52      58      +6
pick_sighandler                                       62      65      +3
execvp_or_die                                         85      88      +3
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 8/0 up/down: 120/0)             Total: 120 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

5 files changed, 133 insertions, 15 deletions

diff --git a/shell/ash_test/ash-getopts/getopt_nested.right b/shell/ash_test/ash-getopts/getopt_nested.right
new file mode 100644
index 000000000..b0c339db1
--- /dev/null
+++ b/shell/ash_test/ash-getopts/getopt_nested.right
@@ -0,0 +1,14 @@
+var:a
+var:b
+var:c
+var:a
+var:b
+var:c
+Illegal option -d
+var:?
+Illegal option -e
+var:?
+Illegal option -f
+var:?
+var:a
+End: var:? OPTIND:6
diff --git a/shell/ash_test/ash-getopts/getopt_nested.tests b/shell/ash_test/ash-getopts/getopt_nested.tests
new file mode 100755
index 000000000..1b48b4075
--- /dev/null
+++ b/shell/ash_test/ash-getopts/getopt_nested.tests
@@ -0,0 +1,21 @@
+# Test that there is no interference of getopt()
+# in getopts and unset.
+# It's unclear what "correct" OPTIND values should be
+# for "b" and "c" results from "-bc": 2? 3?
+# What we focus on here is that all options are reported
+# correct number of times and in correct sequence.
+
+(
+
+loop=99
+while getopts "abc" var -a -bc -abc -def -a; do
+    echo "var:$var" #OPTIND:$OPTIND
+    # this may use getopt():
+    unset -ff func
+    test $((--loop)) = 0 && break  # BUG if this triggers
+done
+echo "End: var:$var OPTIND:$OPTIND"
+
+) 2>&1 \
+| sed   -e 's/ unrecognized option: / invalid option -- /' \
+        -e 's/ illegal option -- / invalid option -- /' \
diff --git a/shell/hush.c b/shell/hush.c
index cdc3a8618..ceb8cbb0a 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -907,6 +907,9 @@ struct globals {
         unsigned depth_break_continue;
         unsigned depth_of_loop;
 #endif
+#if ENABLE_HUSH_GETOPTS
+        unsigned getopt_count;
+#endif
         const char *ifs;
         const char *cwd;
         struct variable *top_var;
@@ -2214,6 +2217,10 @@ static int set_local_var(char *str, unsigned flags)
                 cur->flg_export = 1;
         if (name_len == 4 && cur->varstr[0] == 'P' && cur->varstr[1] == 'S')
                 cmdedit_update_prompt();
+#if ENABLE_HUSH_GETOPTS
+        if (strncmp(cur->varstr, "OPTIND=", 7) == 0)
+                G.getopt_count = 0;
+#endif
         if (cur->flg_export) {
                 if (flags & SETFLAG_UNEXPORT) {
                         cur->flg_export = 0;
@@ -2244,6 +2251,10 @@ static int unset_local_var_len(const char *name, int name_len)
 
         if (!name)
                 return EXIT_SUCCESS;
+#if ENABLE_HUSH_GETOPTS
+        if (name_len == 6 && strncmp(name, "OPTIND", 6) == 0)
+                G.getopt_count = 0;
+#endif
         var_pp = &G.top_var;
         while ((cur = *var_pp) != NULL) {
                 if (strncmp(cur->varstr, name, name_len) == 0 && cur->varstr[name_len] == '=') {
@@ -9889,7 +9900,8 @@ Test that VAR is a valid variable name?
 */
         char cbuf[2];
         const char *cp, *optstring, *var;
-        int c, exitcode;
+        int c, n, exitcode, my_opterr;
+        unsigned count;
 
         optstring = *++argv;
         if (!optstring || !(var = *++argv)) {
@@ -9897,17 +9909,18 @@ Test that VAR is a valid variable name?
                 return EXIT_FAILURE;
         }
 
-        c = 0;
+        if (argv[1])
+                argv[0] = G.global_argv[0]; /* for error messages in getopt() */
+        else
+                argv = G.global_argv;
+        cbuf[1] = '\0';
+
+        my_opterr = 0;
         if (optstring[0] != ':') {
                 cp = get_local_var_value("OPTERR");
                 /* 0 if "OPTERR=0", 1 otherwise */
-                c = (!cp || NOT_LONE_CHAR(cp, '0'));
+                my_opterr = (!cp || NOT_LONE_CHAR(cp, '0'));
         }
-        opterr = c;
-        cp = get_local_var_value("OPTIND");
-        optind = cp ? atoi(cp) : 0;
-        optarg = NULL;
-        cbuf[1] = '\0';
 
         /* getopts stops on first non-option. Add "+" to force that */
         /*if (optstring[0] != '+')*/ {
@@ -9916,11 +9929,47 @@ Test that VAR is a valid variable name?
                 optstring = s;
         }
 
-        if (argv[1])
-                argv[0] = G.global_argv[0]; /* for error messages */
-        else
-                argv = G.global_argv;
-        c = getopt(string_array_len(argv), argv, optstring);
+        /* Naively, now we should just
+         *      cp = get_local_var_value("OPTIND");
+         *      optind = cp ? atoi(cp) : 0;
+         *      optarg = NULL;
+         *      opterr = my_opterr;
+         *      c = getopt(string_array_len(argv), argv, optstring);
+         * and be done? Not so fast...
+         * Unlike normal getopt() usage in C programs, here
+         * each successive call will (usually) have the same argv[] CONTENTS,
+         * but not the ADDRESSES. Worse yet, it's possible that between
+         * invocations of "getopts", there will be calls to shell builtins
+         * which use getopt() internally. Example:
+         *      while getopts "abc" RES -a -bc -abc de; do
+         *              unset -ff func
+         *      done
+         * This would not work correctly: getopt() call inside "unset"
+         * modifies internal libc state which is tracking position in
+         * multi-option strings ("-abc"). At best, it can skip options
+         * or return the same option infinitely. With glibc implementation
+         * of getopt(), it would use outright invalid pointers and return
+         * garbage even _without_ "unset" mangling internal state.
+         *
+         * We resort to resetting getopt() state and calling it N times,
+         * until we get Nth result (or failure).
+         * (N == G.getopt_count is reset to 0 whenever OPTIND is [un]set).
+         */
+        optind = 0; /* reset getopt() state */
+        count = 0;
+        n = string_array_len(argv);
+        do {
+                optarg = NULL;
+                opterr = (count < G.getopt_count) ? 0 : my_opterr;
+                c = getopt(n, argv, optstring);
+                if (c < 0)
+                        break;
+                count++;
+        } while (count <= G.getopt_count);
+
+        /* Set OPTIND. Prevent resetting of the magic counter! */
+        set_local_var_from_halves("OPTIND", utoa(optind));
+        G.getopt_count = count; /* "next time, give me N+1'th result" */
 
         /* Set OPTARG */
         /* Always set or unset, never left as-is, even on exit/error:
@@ -9949,10 +9998,9 @@ Test that VAR is a valid variable name?
                 c = '?';
         }
 
-        /* Set VAR and OPTIND */
+        /* Set VAR */
         cbuf[0] = c;
         set_local_var_from_halves(var, cbuf);
-        set_local_var_from_halves("OPTIND", utoa(optind));
 
         return exitcode;
 }
diff --git a/shell/hush_test/hush-getopts/getopt_nested.right b/shell/hush_test/hush-getopts/getopt_nested.right
new file mode 100644
index 000000000..0218dba56
--- /dev/null
+++ b/shell/hush_test/hush-getopts/getopt_nested.right
@@ -0,0 +1,14 @@
+var:a
+var:b
+var:c
+var:a
+var:b
+var:c
+./getopt_nested.tests: invalid option -- d
+var:?
+./getopt_nested.tests: invalid option -- e
+var:?
+./getopt_nested.tests: invalid option -- f
+var:?
+var:a
+End: var:? OPTIND:6
diff --git a/shell/hush_test/hush-getopts/getopt_nested.tests b/shell/hush_test/hush-getopts/getopt_nested.tests
new file mode 100755
index 000000000..1b48b4075
--- /dev/null
+++ b/shell/hush_test/hush-getopts/getopt_nested.tests
@@ -0,0 +1,21 @@
+# Test that there is no interference of getopt()
+# in getopts and unset.
+# It's unclear what "correct" OPTIND values should be
+# for "b" and "c" results from "-bc": 2? 3?
+# What we focus on here is that all options are reported
+# correct number of times and in correct sequence.
+
+(
+
+loop=99
+while getopts "abc" var -a -bc -abc -def -a; do
+    echo "var:$var" #OPTIND:$OPTIND
+    # this may use getopt():
+    unset -ff func
+    test $((--loop)) = 0 && break  # BUG if this triggers
+done
+echo "End: var:$var OPTIND:$OPTIND"
+
+) 2>&1 \
+| sed   -e 's/ unrecognized option: / invalid option -- /' \
+        -e 's/ illegal option -- / invalid option -- /' \