[Vm-dev] Portability problems: compiler flags

[Henrik Sperre Johansen]

Please read this thread from a month ago.

http://forum.world.st/Failed-to-build-FloatMathPlugin-on-FreeBSD-td3346374.html#a3346695

Cheers,
Henry

On 10.04.2011 21:17, Mariano Martinez Peck wrote:
>   
>
>
>
>
> On Sun, Apr 10, 2011 at 9:08 PM, Andreas Raab <andreas.raab at gmx.de 
> <mailto:andreas.raab at gmx.de>> wrote:
>
>
>     On 4/10/2011 18:35, Mariano Martinez Peck wrote:
>>     Sorry for arriving late to the thread. I have a simiar problem
>>     now trying to compile Cog in a Windows box with MinGW.
>>
>>     The problem is described in another thread:
>>     http://forum.world.st/Cannot-generate-VM-in-Windows-with-CMake-and-Git-tp3434566p3434566.html
>>
>>     So...if we remove "-mno-fused-madd"  from windows confs like
>>     CogMsWindowsConfig, then Corquet wouldn't behave correctly ?  but
>>     if we keep them, it is difficult to compile in some platforms.
>>     So...I wonder, I am the only one trying to compile this on
>>     Windows?  Who do the Croquet guys do to compile with this flag in
>>     Windows?
>
>     gcc 3.x accepts -mno-fused-madd fine.
>
>
> Weird...I have
>
> $ gcc --version
> gcc.exe (GCC) 3.4.5 (mingw-vista special r3)
> Copyright (C) 2004 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even fo
>
> and I have the error:
>
> Scanning dependencies of target FloatMathPlugin
> [ 13%] Building C object 
> FloatMathPlugin/CMakeFiles/FloatMathPlugin.dir/C_/maria                   
> no/squeak/vm/cogVM/blessed/src/plugins/FloatMathPlugin/FloatMathPlugin.c.obj
> cc1.exe: error: invalid option `no-fused-madd'
> make[2]: *** 
> [FloatMathPlugin/CMakeFiles/FloatMathPlugin.dir/C_/mariano/squeak/v                   
> m/cogVM/blessed/src/plugins/FloatMathPlugin/FloatMathPlugin.c.obj] Error 1
> make[1]: *** [FloatMathPlugin/CMakeFiles/FloatMathPlugin.dir/all] Error 2
> make: *** [all] Error 2
> r MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>
>
> Cheers
>
> mariano
>
>
>     Cheers,
>       - Andreas
>
>>
>>     Thanks
>>
>>     Mariano
>>
>>     On Tue, Jan 25, 2011 at 9:05 PM, Nicolas Cellier
>>     <nicolas.cellier.aka.nice at gmail.com
>>     <mailto:nicolas.cellier.aka.nice at gmail.com>> wrote:
>>
>>
>>         2011/1/25 Andreas Raab <andreas.raab at gmx.de
>>         <mailto:andreas.raab at gmx.de>>:
>>         >
>>         > On 1/25/2011 11:38 AM, Igor Stasenko wrote:
>>         >>>
>>         >>> Squeak uses highly unportable flag "-mno-fused-madd".
>>         >>> It isn't present in many systems, even those using GCC,
>>         >>> since many systems use older compilers.
>>         >>>
>>         >>> Also, why do you build fdlibm? It is old stuff that works
>>         not so well,
>>         >>> we have better libm. Is there a way to use our libm?
>>         >>>
>>         >> I asked  same question few weeks ago.
>>         >> Check mailing list archive for discussion.
>>         >> In short: differrent libm implementations work differently
>>         and some
>>         >> have bad support of IEEE standard.
>>         >
>>         > Actually, that's not quite the point. The issue is that
>>         Croquet requires
>>         > bit-identical computations including floating point. For
>>         FPU computations,
>>         > the use of -mno-fused-madd avoids the use of the fused
>>         multiply-add
>>         > operation by compilers which support it which would
>>         generate different
>>         > results from compilers not using fused madd.
>>         >
>>         > The usage of fdlibm is similar. As Nicolas has pointed out
>>         elsewhere, fdlibm
>>         > is in some cases actually inferior of the platform libms
>>         (one might say
>>         > outright broken) but the requirement for the usage in
>>         Croquet isn't really
>>         > whether it's "correct" or "good". The requirement is
>>         bit-identical results
>>         > across all platforms. The results can be wrong as long as
>>         they are
>>         > consistently wrong. But they mustn't be different.
>>         >
>>
>>         Yes, I was disappointed by exp(1), but fdlibm sin(pi+epsilon)
>>         is far
>>         far superior to i86 hardwired answer (i86 approximation of pi
>>         is well
>>         known to be poor).
>>
>>         Nicolas
>>
>>         > Having said that, for your regular Squeak VM (i.e., not
>>         requiring
>>         > bit-identical floating point results) there really isn't a
>>         requirement to
>>         > use either -mno-fused-madd or fdlibm.
>>         >
>>         > Cheers,
>>         >  - Andreas
>>         >
>>
>>
>>
>>
>>     -- 
>>     Mariano
>>     http://marianopeck.wordpress.com
>>
>
>
>
>
> -- 
> Mariano
> http://marianopeck.wordpress.com
>

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