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Re: GCC 3.3.1 problem with printf %Lg %Lg and -m128bit-long-double compile option
- From: Brian Ford <ford at vss dot fsi dot com>
- To: mathias dot wagner at philips dot com
- Cc: cygwin at cygwin dot com
- Date: Fri, 28 May 2004 10:54:37 -0500
- Subject: Re: GCC 3.3.1 problem with printf %Lg %Lg and -m128bit-long-double compile option
- References: <OF4B525423.BF84D3AE-ONC1256EA2.00331803-C1256EA2.003360F4@philips.com>
- Reply-to: cygwin at cygwin dot com
On Fri, 28 May 2004, mathias.wagner wrote:
> To: "Gerrit @ cygwin" <cygwin at cygwin dot com>
http://www.cygwin.com/acronyms/#PCYMTNQREAIYR
> Meanwhile I have had some help from another colleague here at Philips and
> he found out that the -m96bit-long-double compile option works fine.
My understanding is that this is the default ie. no switch requried.
> Note that 96 bit is what a long double takes. This makes sense in
> conjunction with what Brian said: The alignment of the parameters handed
> over to a function is changed when using -m128bit-long-double, and hence
> all functions affected must be recompiled - so presumably cygwin itself.
Yes.
> There was no particular reason for using -m128bit-long-double other than
> that I have always used it, and I will switch to -m96bit-long-double.
It might have performed better with respect to caching, but YMMV.
> But perhaps one could insert somewhere in gcc a warning when using such
> a combination of compile options. I know it is in the documentation
> somewhere, but compiler warnings are much more visible... :-)
You could take this up on the gcc list if it is still important to you,
but I suspect they would frown on the idea. The philosophy goes
something like this:
You had to read the documentation to discover that this switch existed.
It is not a compiler warnings job to advise you to read the documentation
more carefully. It would also penalize those that did read the docs, so
they would want a way to turn off the gratuitous warning with via another
switch or attribute.
Can you see why this isn't a good idea?
--
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained pilot...
--
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