From: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
---|---|
To: | <lockhart(at)fourpalms(dot)org> |
Cc: | Lamar Owen <lamar(dot)owen(at)wgcr(dot)org>, <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: RPM building (was regression on RedHat) |
Date: | 2001-03-21 18:35:00 |
Message-ID: | Pine.LNX.4.30.0103211931270.1694-100000@peter.localdomain |
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Lists: | pgsql-hackers |
Thomas Lockhart writes:
> Mandrake (as of 7.2) still does a brain-dead mix of "-O3" and
> "-ffast-math", which is a risky and unnecessary combination according to
> the gcc folks (and which kills some of our date/time rounding). From the
> man page for gcc:
>
> -ffast-math
> This option should never be turned on by any `-O' option
> since it can result in incorrect output for programs which
> depend on an exact implementation of IEEE or ANSI
> rules/specifications for math functions.
You're reading this wrong. What this means is:
"If you're working on GCC, do not ever think of enabling -ffast-math
implicitly by any -Ox level [since most other -fxxx options are grouped
under some -Ox], since programs that might want optimization could still
depend on correct IEEE math."
In particular, Mandrake is not wrong to compile with -O3 and -ffast-math.
The consequence would only be slightly incorrect math results, and that is
what indeed happened.
--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/
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