From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: GCC 7 warnings
Date: Wed, 12 Apr 2017 00:12:10 -0400
Message-ID: <24498.1491970330@sss.pgh.pa.us> (raw)
In-Reply-To: <c4e7f361-358b-45f9-bbe4-e167fa4de16c@2ndquadrant.com>
References: <20170411175708.coshtfzejgaqhar2@alvherre.pgsql>
<c4e7f361-358b-45f9-bbe4-e167fa4de16c@2ndquadrant.com>
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Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> Attached is a more refined patch that I propose for PG10 now. Compared
> to the previous rushed version, this one uses some more precise
> arithmetic to size some of the buffers.
Generally +1 for switching the snprintf calls to use sizeof() rather
than repeating the declared sizes of the arrays.
The change in setup_formatted_log_time seems a bit weird:
- char msbuf[8];
+ char msbuf[10];
The associated call is
sprintf(msbuf, ".%03d", (int) (saved_timeval.tv_usec / 1000));
Now a human can see that saved_timeval.tv_usec must be 0..999999, so
that the %d format item must always emit exactly 3 characters, which
means that really 5 bytes would be enough. I wouldn't expect a
compiler to know that, but if it's making a generic assumption about
the worst-case width of %d, shouldn't it conclude that we might need
as many as 13 bytes for the buffer? Why does msbuf[10] satisfy it
if msbuf[8] doesn't?
IOW, if we're going to touch this at all, I'd be inclined to go with
msbuf[16] or so, as being more likely to satisfy compilers that have
decided to try to warn about this. And maybe we should use snprintf,
just for luck.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, peter.eisentraut@2ndquadrant.com, alvherre@2ndquadrant.com
Subject: Re: GCC 7 warnings
In-Reply-To: <24498.1491970330@sss.pgh.pa.us>
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