5 files changed, 58 insertions, 15 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 1d2826d9a..46bb7e9a2 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -2185,7 +2185,7 @@ static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg, char
 
         ored_ch = 0;
 
-        debug_printf_expand("expand_vars_to_list: arg '%s'\n", arg);
+        debug_printf_expand("expand_vars_to_list: arg:'%s' or_mask:%x\n", arg, or_mask);
         debug_print_list("expand_vars_to_list", output, n);
         n = o_save_ptr(output, n);
         debug_print_list("expand_vars_to_list[0]", output, n);
@@ -3425,7 +3425,7 @@ static void pseudo_exec_argv(nommu_save_t *nommu_save,
         sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);
         execvp(argv[0], argv);
         bb_perror_msg("can't execute '%s'", argv[0]);
-        _exit(EXIT_FAILURE);
+        _exit(127); /* bash compat */
 }
 
 /* Called after [v]fork() in run_pipe
@@ -3895,7 +3895,7 @@ static NOINLINE int run_pipe(struct pipe *pi)
                         argv_expanded = expand_strvec_to_strvec(argv + command->assignment_cnt);
                 }
 
-                /* if someone gives us an empty string: ``, $(), ... */
+                /* if someone gives us an empty string: `cmd with empty output` */
                 if (!argv_expanded[0]) {
                         debug_leave();
                         return 0;
@@ -5802,7 +5802,7 @@ static int parse_stream_dquoted(o_string *as_string,
         if (ch != '\n') {
                 next = i_peek(input);
         }
-        debug_printf_parse(": ch=%c (%d) escape=%d\n",
+        debug_printf_parse("\" ch=%c (%d) escape=%d\n",
                                         ch, ch, dest->o_escape);
         if (ch == '\\') {
                 if (next == EOF) {
@@ -5882,6 +5882,11 @@ static struct pipe *parse_stream(char **pstring,
                         end_trigger ? end_trigger : 'X');
         debug_enter();
 
+        /* If very first arg is "" or '', dest.data may end up NULL.
+         * Preventing this: */
+        o_addchr(&dest, '\0');
+        dest.length = 0;
+
         G.ifs = get_local_var_value("IFS");
         if (G.ifs == NULL)
                 G.ifs = " \t\n";
@@ -6979,16 +6984,32 @@ static int FAST_FUNC builtin_cd(char **argv)
 
 static int FAST_FUNC builtin_exec(char **argv)
 {
-        if (*++argv == NULL)
-                return EXIT_SUCCESS; /* bash does this */
-        {
+        static const char pseudo_null_str[] = { SPECIAL_VAR_SYMBOL, SPECIAL_VAR_SYMBOL, '\0' };
+        char **pp = argv;
 #if !BB_MMU
-                nommu_save_t dummy;
+        nommu_save_t dummy;
 #endif
-                /* TODO: if exec fails, bash does NOT exit! We do... */
-                pseudo_exec_argv(&dummy, argv, 0, NULL);
-                /* never returns */
+
+        if (*++argv == NULL)
+                return EXIT_SUCCESS; /* bash does this */
+
+        /* Make sure empty arguments aren't ignored */
+        /* Example: exec ls '' */
+        pp = argv;
+        while (*pp) {
+                if ((*pp)[0] == '\0')
+                        *pp = (char*)pseudo_null_str;
+                pp++;
         }
+
+        /* Careful: we can end up here after [v]fork. Do not restore
+         * tty pgrp then, only top-level shell process does that */
+        if (G_saved_tty_pgrp && getpid() == G.root_pid)
+                tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);
+
+        /* TODO: if exec fails, bash does NOT exit! We do... */
+        pseudo_exec_argv(&dummy, argv, 0, NULL);
+        /* never returns */
 }
 
 static int FAST_FUNC builtin_exit(char **argv)
diff --git a/shell/hush_test/hush-misc/empty_args.right b/shell/hush_test/hush-misc/empty_args.right
new file mode 100644
index 000000000..38ed8b8be
--- /dev/null
+++ b/shell/hush_test/hush-misc/empty_args.right
@@ -0,0 +1,6 @@
+Null 0th arg:
+hush: can't execute '': No such file or directory
+127
+Null 1st arg:
+0
+Null arg in exec:
diff --git a/shell/hush_test/hush-misc/empty_args.tests b/shell/hush_test/hush-misc/empty_args.tests
new file mode 100755
index 000000000..efce5494a
--- /dev/null
+++ b/shell/hush_test/hush-misc/empty_args.tests
@@ -0,0 +1,9 @@
+echo Null 0th arg:
+""
+echo $?
+echo Null 1st arg:
+# printf without args would print usage info
+printf ""
+echo $?
+echo Null arg in exec:
+exec printf ""
diff --git a/shell/hush_test/hush-psubst/emptytick.right b/shell/hush_test/hush-psubst/emptytick.right
index d4b70c58a..1f60ecfda 100644
--- a/shell/hush_test/hush-psubst/emptytick.right
+++ b/shell/hush_test/hush-psubst/emptytick.right
@@ -1,14 +1,17 @@
 0
 0
+hush: can't execute '': No such file or directory
 0
+hush: can't execute '': No such file or directory
 0
 0
 0
 0
 0
+hush: can't execute '': No such file or directory
 0
+hush: can't execute '': No such file or directory
 0
 0
 0
-0
-0
+hush: can't execute '': No such file or directory
diff --git a/shell/hush_test/hush-psubst/emptytick.tests b/shell/hush_test/hush-psubst/emptytick.tests
index af3a1836c..a269f025a 100755
--- a/shell/hush_test/hush-psubst/emptytick.tests
+++ b/shell/hush_test/hush-psubst/emptytick.tests
@@ -1,16 +1,20 @@
 true;  ``; echo $?
 false; ``; echo $?
+# UNFIXED BUG. bash sets $? to 127:
 true;  `""`; echo $?
+# bash sets $? to 127:
 false; `""`; echo $?
 true;  `     `; echo $?
 false; `     `; echo $?
 
 true;  $(); echo $?
 false; $(); echo $?
+# bash sets $? to 127:
 true;  $(""); echo $?
+# bash sets $? to 127:
 false; $(""); echo $?
 true;  $(     ); echo $?
 false; $(     ); echo $?
 
-true;  exec ''; echo $?
-false; exec ''; echo $?
+exec ''; echo $?
+echo Not reached