> The strncat man page (and similarly the C99 standard) says: "[...] the size of dest must be at least strlen(dest)+n+1." No, the standard does not say that.

> The strncat man page (and similarly the C99 standard) says: "[...] the size of dest must be at least strlen(dest)+n+1." No, the standard does not say that. It (both C99 and C11) says, verbatim: "the maximum number of characters that can end up in the array pointed to by s1 is strlen(s1)+n+1." If the manpage on your system says that, that's a fairly serious deficiency in the manpage. The standard also says "characters that follow it [a null character] are not appended", so copying extra bytes is explicitly not correct.