2 files changed, 19 insertions, 9 deletions

diff --git a/coreutils/printf.c b/coreutils/printf.c
index a14306f5a..d877e0581 100644
--- a/coreutils/printf.c
+++ b/coreutils/printf.c
@@ -33,7 +33,8 @@
    The 'format' argument is re-used as many times as necessary
    to convert all of the given arguments.
 
-   David MacKenzie <djm@gnu.ai.mit.edu> */
+   David MacKenzie <djm@gnu.ai.mit.edu>
+*/
 
 
 //   19990508 Busy Boxed! Dave Cinege
@@ -251,10 +252,12 @@ static char **print_formatted(char *f, char **argv)
                                 ++f;
                                 ++direc_length;
                         }
-                        /*
-                        if (!strchr ("diouxXfeEgGcs", *f))
-                        fprintf(stderr, "%%%c: invalid directive", *f);
-                        */
+                        /* needed - try "printf %" without it */
+                        if (!strchr("diouxXfeEgGcs", *f)) {
+                                bb_error_msg("invalid directive '%s'", direc_start);
+                                /* causes main() to exit with error */
+                                return saved_argv - 1;
+                        }
                         ++direc_length;
                         if (*argv) {
                                 print_direc(direc_start, direc_length, field_width,
@@ -285,7 +288,8 @@ int printf_main(int argc UNUSED_PARAM, char **argv)
         char **argv2;
 
         /* We must check that stdout is not closed.
-         * The reason for this is highly non-obvious. printf_main is used from shell.
+         * The reason for this is highly non-obvious.
+         * printf_main is used from shell.
          * Shell must correctly handle 'printf "%s" foo'
          * if stdout is closed. With stdio, output gets shoveled into
          * stdout buffer, and even fflush cannot clear it out. It seems that
@@ -298,7 +302,7 @@ int printf_main(int argc UNUSED_PARAM, char **argv)
         /* bash builtin errors out on "printf '-%s-\n' foo",
          * coreutils-6.9 works. Both work with "printf -- '-%s-\n' foo".
          * We will mimic coreutils. */
-        if (argv[1] && argv[1][0] == '-' && argv[1][1] == '-' && argv[1][2] == '\0')
+        if (argv[1] && argv[1][0] == '-' && argv[1][1] == '-' && !argv[1][2])
                 argv++;
         if (!argv[1])
                 bb_show_usage();
@@ -309,12 +313,12 @@ int printf_main(int argc UNUSED_PARAM, char **argv)
         do {
                 argv = argv2;
                 argv2 = print_formatted(format, argv);
-        } while (argv2 != argv && *argv2);
+        } while (argv2 > argv && *argv2);
 
         /* coreutils compat (bash doesn't do this):
         if (*argv)
                 fprintf(stderr, "excess args ignored");
         */
 
-        return EXIT_SUCCESS;
+        return (argv2 < argv); /* if true, print_formatted errored out */
 }
diff --git a/testsuite/printf.tests b/testsuite/printf.tests
index 18f25e3f1..d6b60fb8c 100755
--- a/testsuite/printf.tests
+++ b/testsuite/printf.tests
@@ -24,4 +24,10 @@ testing "printf repeatedly use pattern for each argv" \
         "foo\n$HOME\n" \
         "" ""
 
+# Why ()s are necessary I have no idea...
+testing "printf aborts on bare %" \
+        "(${bb}printf '%' a b c) 2>&1; echo \$?" \
+        "printf: invalid directive '%'\n""1\n" \
+        "" ""
+
 exit $FAILCOUNT