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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Lukas Fittl <lukas@fittl.com>
Cc: Haibo Yan <tristan.yim@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: David Geier <geidav.pg@gmail.com>
Subject: Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?
Date: Sun, 12 Apr 2026 14:20:31 -0400
Message-ID: <343362.1776018031@sss.pgh.pa.us> (raw)
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Lukas Fittl <lukas@fittl.com> writes:
> FWIW, for archive's sake, drongo is green again now, thanks to commit
> 7fc36c5db550 (Avoid CPUID 0x15/0x16 for Hypervisor TSC frequency).

drongo may be happy, but Coverity is not:

166     	uint64		loop_count;
167     
168     	loop_count = test_timing(test_duration, TIMING_CLOCK_SOURCE_SYSTEM, false);
>>>     CID 1691465:         Incorrect expression  (DIVIDE_BY_ZERO)
>>>     In function call "output", division by expression "loop_count" which may be zero has undefined behavior.
169     	output(loop_count);

AFAICS it's correct to complain.  test_timing() visibly can return zero,
but of the three places where test_timing() is followed by output()
only one has a defense against that.

			regards, tom lane





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