RFR: 8254270: linux 32 bit build doesn't compile libjdwp/log_messages.c

[Thomas Stuefe]

On Thu, 5 Nov 2020 17:57:29 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>>> While it's possible that these warnings on 32-bit builds is just a matter of the compiler being wrong, it could also be that it can't determine all arguments are null-terminated. Specifying max string length in format specifiers seem a benign and cheap safeguard.
>> 
>> I don't think this is the case. If you assume the arguments are not null terminated, then there is no limit to how long the string could be, where-as the error messages are very specific with the (incorrectly) calculated range of potential overflow.
>
>> I don't think this is the case. If you assume the arguments are not null terminated, then there is no limit to how long the string could be, where-as the error messages are very specific with the (incorrectly) calculated range of potential overflow.
> 
> I must be missing what you're suggesting here?

Hi,

I think the compiler is correct. The 3 in "%.3d" of the second argument is precision, not scale. Which is the *minimum* numbers of digits to be printed.

So we get:

    (void)snprintf(tbuf, ltbuf,
                   "%s.%.3d %s", timestamp_date_time,
                   (int)(millisecs), timestamp_timezone);

with timestamp_date_time = DT_SIZE = 20 and timestamp_timezone = TZ_SIZE = 56

and the second argument prints at least three digits but possibly more if the argument is longer. MAX_INT is 2147483647. So length could be 10.

56 + 20 + 10 = 86.

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PR: https://git.openjdk.java.net/jdk/pull/1067