Re: Very weird assembly failure (was Re: UP kernel performance andMatt Dillon's patches)

[Bruce Evans]

On Wed, 29 Mar 2000, Matthew Dillon wrote:

> :Gas notices the problem for "movl $-FOO,%eax":
> :    z.s: Assembler messages:
> :    z.s:1: Error: Negative of non-absolute symbol FOO
> :Similarly for the a.out case.  Complementation is equivalent to negation
> :on 2's complement machines, so gas should produce this error for $~FOO too.
> 
>     Ok, so who do we send your excellent analysis to at GNU-C?  I think
>     this is a rather serious bug myself since a programmer can make a
>     simple labelname mistake and get incorrect code instead of an error.

Don't know.  David O'Brien has been doing most of the GNU contacting.

>     Also, probably a simple mistake but complement != negation.  
>     I think ~F = -F - 1;

I meant that has equivalent complexity.  All normal assemblers and
object formats handle offsets, so if they can handle "~" then they
can probably handle "-".

Bruce



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