diff mbox

[v1] Add Reiwa era tests to time/tst-strftime3.c

Message ID xnpnq4lzm6.fsf@greed.delorie.com
State Committed
Headers

Commit Message

DJ Delorie April 3, 2019, 12:08 a.m. UTC 
  Steve Ellcey <sellcey@marvell.com> writes:
> I am building ToT glibc with ToT gcc and during glibc testing I got
> this error:

Yup, Arjun noticed as well when trying in Rawhide.  It's a wierd
warning, too, because the *point* of snprintf is that it truncates the
output.

Arjun and I talked about a few options, but I think the simplest is to
just shut gcc up...  alternatives include far bigger buffers with
sprintf, or xasprintf... but what's the point of snprintf at all then?

Comments

Andreas Schwab April 3, 2019, 7:08 a.m. UTC | #1 
On Apr 02 2019, DJ Delorie <dj@redhat.com> wrote:

> Steve Ellcey <sellcey@marvell.com> writes:
>> I am building ToT glibc with ToT gcc and during glibc testing I got
>> this error:
>
> Yup, Arjun noticed as well when trying in Rawhide.  It's a wierd
> warning, too, because the *point* of snprintf is that it truncates the
> output.
>
> Arjun and I talked about a few options, but I think the simplest is to
> just shut gcc up...  alternatives include far bigger buffers with
> sprintf, or xasprintf... but what's the point of snprintf at all then?
>
>
> diff --git a/time/tst-strftime3.c b/time/tst-strftime3.c
> index 32ce0d93e2..2a4c3ea398 100644
> --- a/time/tst-strftime3.c
> +++ b/time/tst-strftime3.c
> @@ -430,16 +430,21 @@ static void
>  tm_to_printed (struct tm *tm, char *buffer)
>  {
>    const char *wn;
> -  char temp[50];
> +  char temp[28];
>  
>    if (0 <= tm->tm_wday && tm->tm_wday <= 6)
>      wn = weekday_name[tm->tm_wday];

Does it change anything if you make weekday_name const or static?

Andreas.
Andreas Schwab April 3, 2019, 7:13 a.m. UTC | #2 
On Apr 02 2019, DJ Delorie <dj@redhat.com> wrote:

> Yup, Arjun noticed as well when trying in Rawhide.  It's a wierd
> warning, too, because the *point* of snprintf is that it truncates the
> output.

The point of -Wformat-truncation is to warn if snprintf results in
incomplete output, which is a generally a bug.  If you want to truncate
a string argument, use %s with a precision.

Andreas.
diff mbox

Patch

diff --git a/time/tst-strftime3.c b/time/tst-strftime3.c
index 32ce0d93e2..2a4c3ea398 100644
--- a/time/tst-strftime3.c
+++ b/time/tst-strftime3.c
@@ -430,16 +430,21 @@  static void
 tm_to_printed (struct tm *tm, char *buffer)
 {
   const char *wn;
-  char temp[50];
+  char temp[28];
 
   if (0 <= tm->tm_wday && tm->tm_wday <= 6)
     wn = weekday_name[tm->tm_wday];
   else
     {
       wn = temp;
+      /* 64-bit values need at most 21 bytes, including NUL.  */
       sprintf (temp, "%d", tm->tm_wday);
     }
 
+  /* This will be at most 4+2+2+2+2+2+7+20 = 41 bytes long, including
+     NUL.  GCC warns if snprintf may truncate the output, which is why
+     we're using snprintf...  */
+#pragma GCC diagnostic ignored "-Wformat-truncation="
   snprintf (buffer, TMBUFLEN, "%04d/%02d/%02d %02d:%02d:%02d %s",
 	    tm->tm_year + 1900,
 	    tm->tm_mon + 1,