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Re: Overflow fix (was Problems with trampoline.S with 64 bit binutils)


On 28 Jul 1999, Ian Lance Taylor wrote:

>    Date: Wed, 28 Jul 1999 18:39:18 +0930 (CST)
>    From: Alan Modra <alan@SPRI.Levels.UniSA.Edu.Au>
> 
>    Is it OK for me to check this one in, Ian?  It's almost in the "obvious
>    fix" category...
> 
> Almost.
> 
>    > +	      mask <<= size * 8 - (fixP->fx_signed ? 1 : 0);
> 
> If size is 4 and fixP->fx_signed is not set, then this will do a left
> shift by 32.  If mask is itself 32 bits, then this is not defined by
> ANSI C.  There are in fact compilers which will turn this into a
> no-op: they generate a shift by 32 instruction, which is masked into a
> shift by 0 instruction.
> 
> That's why I had the two shifts in the old code, and I think we need
> to keep that.

size == 4  =>  sizeof (mask) > 4.  Surely ANSI C doesn't restrict shift
counts of 64 bit quantities to 32??


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