scripts/echo.c: fix NUL handling in "abc\0 def"

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

1 files changed, 21 insertions, 14 deletions

diff --git a/scripts/echo.c b/scripts/echo.c
index 7474ccdd4..e3a07adf0 100644
--- a/scripts/echo.c
+++ b/scripts/echo.c
@@ -153,25 +153,32 @@ int main(int argc, char **argv)
                 if (!eflag) {
                         /* optimization for very common case */
                         fputs(arg, stdout);
-                } else while ((c = *arg++)) {
-                        if (c == eflag) {       /* Check for escape seq. */
+                } else
+                while ((c = *arg++) != '\0') {
+                        if (c == eflag) {
+                                /* This is an "\x" sequence */
+
                                 if (*arg == 'c') {
-                                        /* '\c' means cancel newline and
+                                        /* "\c" means cancel newline and
                                          * ignore all subsequent chars. */
                                         goto ret;
                                 }
-                                {
-                                        /* Since SUSv3 mandates a first digit of 0, 4-digit octals
-                                        * of the form \0### are accepted. */
-                                        if (*arg == '0') {
-                                                /* NB: don't turn "...\0" into "...\" */
-                                                if (arg[1] && ((unsigned char)(arg[1]) - '0') < 8) {
-                                                        arg++;
-                                                }
+                                /* Since SUSv3 mandates a first digit of 0, 4-digit octals
+                                * of the form \0### are accepted. */
+                                if (*arg == '0') {
+                                        if ((unsigned char)(arg[1] - '0') < 8) {
+                                                /* 2nd char is 0..7: skip leading '0' */
+                                                arg++;
                                         }
-                                        /* bb_process_escape_sequence handles NUL correctly
-                                         * ("...\" case. */
-                                        c = bb_process_escape_sequence(&arg);
+                                }
+                                /* bb_process_escape_sequence handles NUL correctly
+                                 * ("...\" case). */
+                                {
+                                        /* optimization: don't force arg to be on-stack,
+                                         * use another variable for that. ~30 bytes win */
+                                        const char *z = arg;
+                                        c = bb_process_escape_sequence(&z);
+                                        arg = z;
                                 }
                         }
                         putchar(c);