[njs] Fixed one byte overread in njs_string_to_c_string().

[Valentin Bartenev]

details:   https://hg.nginx.org/njs/rev/644af379d226
branches:  
changeset: 1068:644af379d226
user:      Valentin Bartenev <vbart at nginx.com>
date:      Thu Jul 25 20:17:42 2019 +0300
description:
Fixed one byte overread in njs_string_to_c_string().

Short strings are packed quite tight in njs_value_t, so there's
no one more byte to test.

    struct {
        njs_value_type_t              type:8;

        uint8_t                       size:4;
        uint8_t                       length:4;

        u_char                        start[14];
    } short_string;

With 14 bytes string this occupies 16 bytes, which is equal
to sizeof(njs_value_t).

diffstat:

 njs/njs_string.c |  5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diffs (15 lines):

diff -r 427edfbe6762 -r 644af379d226 njs/njs_string.c
--- a/njs/njs_string.c	Tue Jul 23 19:42:25 2019 +0300
+++ b/njs/njs_string.c	Thu Jul 25 20:17:42 2019 +0300
@@ -3906,10 +3906,7 @@ njs_string_to_c_string(njs_vm_t *vm, njs
         start = value->short_string.start;
         size = value->short_string.size;
 
-        if (start[size] == '\0') {
-            return start;
-
-        } else if (size < NJS_STRING_SHORT) {
+        if (size < NJS_STRING_SHORT) {
             start[size] = '\0';
             return start;
         }