Re: Bug fix for glibc broke freebsd build in REL_11_STABLE

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>
Cc: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Victor Wagner <vitus(at)wagner(dot)pp(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Bug fix for glibc broke freebsd build in REL_11_STABLE
Date: 2018-09-05 19:16:17
Message-ID: 12736.1536174977@sss.pgh.pa.us
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Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> writes:
> The problem is that if we're relying on -fexcess-precision=standard
> semantics in places besides infinity checks, then we won't get those
> semantics on clang/i386/no-sse2 since it has no comparable option. (What
> are we doing about compilers for x86-32 other than clang and gcc?)

Well, the bigger problem is that we don't really know exactly where
nonstandard precision semantics might cause visible behavior changes.
It's just about a dead certainty, IMO, that there are some other
places we don't know about because the regression tests don't expose
them; or that future code rearrangements might create new problems.

Given that (if I understand Andres correctly) -fexcess-precision=standard
behavior is required by C99, it's hard to get excited about expending
a whole lot of work here. I'm fine with adding some compiler options
or telling the user to do so, but I don't think we should do anything
much beyond that.

regards, tom lane

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