Re: [patch] Fix BZ 18985 out of bounds access in strftime

[Mike Frysinger <vapier at gentoo dot org>]

On 20 Sep 2015 11:45, Paul Pluzhnikov wrote:
> On Sun, Sep 20, 2015 at 11:39 AM, Paul Eggert wrote:
> >>    tp->tm_hour = 1024;
> >>    strftime(..., "%H %I", tp);  // produces "1024 04"
> >>
> >> that doesn't seem very desirable.
> >
> > That helps the programmer more than returning 0 would.
> 
> Yes, you convinced me that returning 0 is the wrong thing to do.
> 
> The remaining question was whether tm_hour==1024 should map to "1024"
> or to "?". Your other example suggests that "1024" is more useful.

as i mentioned in the previous thread, i think dumping more details would
be nicer, and still permissible by the standard.  using tm_hour=1024, we
might have something like:

$ cat test.c
#include <stdio.h>
#include <string.h>
#include <time.h>
int main()
{   
	char buf[1024];
	struct tm tm;
	memset(&tm, 0, sizeof(tm));
	tm.tm_hour = 1024;
	size_t ret = strftime(buf, sizeof(buf), "%H %I", &tm);
	printf("buf = %s\n", buf);
}

$ ./a.out
buf = INVALID<H/tm_hour=1024> 1012

i'm not set on any particular structured format ... just including more
details to make it overly obvious where the problem lies.
-mike

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