From owner-freebsd-java  Tue Mar 16 10:53:43 1999
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From: Nate Williams <nate@mt.sri.com>
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To: SHUDO Kazuyuki <shudoh@muraoka.info.waseda.ac.jp>
Cc: Nate Williams <nate@mt.sri.com>, freebsd-java@FreeBSD.ORG
Subject: Re: jre1.1.7 core dump on FreeBSD 3.1 (intel)
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	<199903110420.NAA03845@cafe.muraoka.info.waseda.ac.jp>
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> FreeBSD don't mask some floating point exceptions which
> are masked on initial state of x87. Overflow(OM),
> Devided by zero(ZM) and illegal operation(IM) aren't
> masked.
> 
> Does JDK for FreeBSD change these FPU exception masks
> from default value?
> 
> We can investigate the states of the masks by the
> following code:
> 
> #include <stdio.h>
> int main(int argc, char **argv) {
>   unsigned short cw;
>   __asm__("fnstcw %0" : "=m"(cw));
>   printf("FPU control word: 0x%04x\n", (int)cw);
>   return 0;
> }
> 
> The code shows FPU control word.
>   On linux:	0x037f
>   On FreeBSD:	0x1272

For what it's worth (this jumped out while I was working on Steve
Price's ELF patches to JDK1.1.7), the FPU mask in the JDK is set to
0x127f.  (See javasrc/src/freebsd/java/green_threads/src/context.c).

I'm not sure what Linux uses, but it may be similar.



Nate


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