commit 039b0a7c37a0916adffbc1a5447dc6796b309cbf
author Olaf Hering <olh@suse.de> Fri Jan 21 19:51:36 2005 +0000
committer H. Peter Anvin <hpa@zytor.com> Fri Jan 21 19:51:36 2005 +0000
tree f5d368d1bafdcdcfd1e725e0e55eb9bb8bb2969b
parent 51d7fe38246ef1e99f0a8f847d6f3f33786bb580

The klibc strncat doesnt behave like described in the man page.
It doesnt terminate the string if size < strlen(src).
It doesnt make dst longer than size.

#include <string.h>
#include <stdio.h>
int main(void)
{
        unsigned char olh[42];
        memset(olh, 'A', sizeof(olh));
        sprintf(olh, "abc");
        fprintf(stderr, "olh: '%s'\n", olh);
        bar(olh, "123456789", 7);
        fprintf(stderr, "olh: '%s'\n", olh);
  return 0;
}

olh: 'abc'
olh: 'abc1234AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA'

klibc/strncat.c

diff --git a/klibc/strncat.c b/klibc/strncat.c
index 0dd9deb..4d8458d 100644
--- a/klibc/strncat.c
+++ b/klibc/strncat.c
@@ -12,14 +12,12 @@
   char ch;
   size_t nn = q-dst;
 
-  if ( __likely(nn <= n) )
-    n -= nn;
-
   while (n--) {
     *q++ = ch = *p++;
     if ( !ch )
-      break;
+      return dst;
   }
+  *q = '\0';
 
   return dst;
 }