On Wed, Oct 23, 2019 at 07:28:48PM +0200, Jakub Jelinek wrote: > On Wed, Oct 23, 2019 at 12:19:10PM -0500, Segher Boessenkool wrote: > > I of course know that for e.g. strcmp or strlen we need to be careful of > > page crossings; but this is strncmp, which has a size argument saying the > > size of the array objects of its arguments! > > https://pubs.opengroup.org/onlinepubs/009695399/functions/strncmp.html > The strncmp() function shall compare not more than n bytes > (bytes that follow a null byte are not compared) > from the array pointed to by s1 to the array pointed to by s2. > > In particular the second line. > > Similarly C11 7.24.4.4: > The strncmp function compares not more than n characters (characters that > follow a > null character are not compared) from the array pointed to by s1 to the array > pointed to > by s2. > > Similarly C99.
Yes, and that does not say you cannot read more characters. It also does not say it compares the strings pointed to, it explicitly says characters from the array pointed to. Segher
