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Re: [avr-gcc-list] math linking problem even with -lm

From: Andrew McNabb
Subject: Re: [avr-gcc-list] math linking problem even with -lm
Date: Tue, 21 Jun 2005 15:24:22 -0600
User-agent: Mutt/

On Tue, Jun 21, 2005 at 10:43:24PM +0200, Joerg Wunsch wrote:

> Order is important when linking.  By the time the linker processes
> your -lm option, it doesn't have anything that needs to be resolved by
> a module found in libm.a, so it proceeds with the next command-line
> argument.  That one will eventually trigger the reference to a symbol
> named "sin", but no further library on the command-line could resolve
> that symbol.

Wow.  That's interesting.  I don't think I ever had that problem with
linking for other platforms, but it sort of makes sense.

I downloaded your Makefile template that Eric referred to, and it works

> Btw., I'd personally avoid using time-consuming functions like
> trigonometrical functions within an interrupt vector.  Heck, I'd avoid
> calling *any* function from within an interrupt vector, as it will
> make the compiler push/pop a lot more registers than needed without
> that.

Yeah.  I was just testing some stuff out.  I'm actually planning on
precomputing a table and then grabbing entries from it in the interrupt
handler.  Is that a reasonable approach?

Thanks a ton for your help.

Andrew McNabb
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