From: Tom Lane <tgl@sss.pgh.pa.us>
To: Lukas Fittl <lukas@fittl.com>
cc: Haibo Yan <tristan.yim@gmail.com>, Andres Freund <andres@anarazel.de>,
        pgsql-hackers <pgsql-hackers@postgresql.org>,
        David Geier <geidav.pg@gmail.com>
Subject: Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?
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Comments: In-reply-to Lukas Fittl <lukas@fittl.com>
	message dated "Sun, 12 Apr 2026 09:38:15 -0700"
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Date: Sun, 12 Apr 2026 14:20:31 -0400
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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 =3D test_timing(test_duration, TIMING_CLOCK_SOURCE_SYS=
TEM, false);
>>>     CID 1691465:         Incorrect expression  (DIVIDE_BY_ZERO)
>>>     In function call "output", division by expression "loop_count" whi=
ch 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