Re: if anyone wanted to practice fixing compiler warnings in tcpdump...

[Guy Harris <gharris () sonic net>]

On Jul 29, 2018, at 5:48 AM, Denis Ovsienko <denis () ovsienko info> wrote:

> ./util-print.c: In function ‘ts_format.isra.0’:
> ./util-print.c:265:27: warning: ‘%06u’ directive output may be truncated writing between 6 and 10 bytes into a region 
> of size between 5 and 12 [-Wformat-truncation=]
> format = "%02d:%02d:%02d.%06u";
>                          ^~~~
> ./util-print.c:265:11: note: using the range [0, 4294967295] for directive argument
> format = "%02d:%02d:%02d.%06u";
>          ^~~~~~~~~~~~~~~~~~~~~
> In file included from /usr/include/stdio.h:862:0,
>                from ./util-print.c:50:
> /usr/include/x86_64-linux-gnu/bits/stdio2.h:64:10: note: ‘__builtin___snprintf_chk’ output between 16 and 27 bytes 
> into a destination of size 21
>  return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>       __bos (__s), __fmt, __va_arg_pack ());
>       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Not formatting to a buffer, but directly printing with ND_PRINT(), should squelch this annoyance; yeah, if the time 
stamp is in seconds/microseconds, and the microseconds value is >= 10^6, something might not be formatted correctly, 
but that's life.  Done in 230e0b85778df66f9cec62d13f0025c78cc0c9da.

I guess we *could* do range checking and print some warning that it's bogus; I'll leave that as an exercise to the 
reader.  (Don't forget to do it for nanosecond-resolution time stamps, too, as 2^32-1 and even 2^31-1 is > 10^9.)
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