[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#32189: 27.0.50; GCC 7 warning due to -Wformat-truncation=2
From: |
Eli Zaretskii |
Subject: |
bug#32189: 27.0.50; GCC 7 warning due to -Wformat-truncation=2 |
Date: |
Wed, 18 Jul 2018 18:09:32 +0300 |
> From: Ken Brown <kbrown@cornell.edu>
> Date: Tue, 17 Jul 2018 15:26:34 -0400
>
> I'm getting the following warning when building the master branch on
> Cygwin with GCC 7.3:
>
> In file included from /usr/include/stdio.h:800:0,
> from ../lib/stdio.h:43,
> from ../../master/src/w32cygwinx.c:22:
> ../../master/src/w32cygwinx.c: In function ‘Fw32_battery_status’:
> ../../master/src/w32cygwinx.c:116:26: warning: ‘%3.1f’ directive output
> may be truncated writing between 3 and 312 bytes into a region of size
> 16 [-Wformat-truncation=]
> snprintf (buffer, 16, "%3.1f", h);
> ^
> ../../master/src/w32cygwinx.c:116:4: note: ‘__builtin_snprintf’ output
> between 4 and 313 bytes into a destination of size 16
> snprintf (buffer, 16, "%3.1f", h);
> ^
Do we really need to use -Wformat-truncation? Is it a useful warning
switch? The above sounds like useless noise, because the code
explicitly _asks_ for truncation. What do people think about this?
> The attached patch avoids the warning. Is this a reasonable fix, or is
> there a better way?
I think if we keep the switch, a better fix is to do this:
snprintf (buffer, 16, "%ld", h % 1000000);
m = seconds_left / 60;
snprintf (buffer, 16, "%ld", m % 20000);
etc., you get the point.
Thanks.