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Re: [avr-libc-dev] Question on Optimizations with Linking

From: Russell Shaw
Subject: Re: [avr-libc-dev] Question on Optimizations with Linking
Date: Thu, 24 Nov 2005 10:39:14 +1100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.11) Gecko/20050914 Debian/1.7.11-1

Colin O'Flynn wrote:

This came out of the discussion with avr-libc about itoa:

Would it be a reasonable idea to change the optimization strategy for linking around a bit? Right now for example we already have a few options for printf, and now are looking at different options for itoa.

Although i think the poll concluded with just using a different name, I like the idea of having the same name but different link options.

What I was proposing was a more intelligent linking operation, basically moving those options out of the Makefile. Then you have a separate file that lists options you want. This has the advantage of supporting a whole slew of options for fine-tuning functions: for example if you need floating point but low accuracy, there could be a small but inaccurate library and a high-end library. It would take advantage of the fact that for open-source you normally have a lot of different implementations with trade-offs that different people value.

As well if you have a separate script or program to deal with the link options, you could end up with a lot smarter link options. For example look for using the floating point with printf when you don't have printf, look for calling math functions without math library, and so on. Then warn the user or link in the proper library based on their settings.

It could be a terrible idea - I'm not familiar enough with the linking strategy. However if it seems reasonable I could try to make a beta version...

I had the idea that instead of having single large libraries such as
stdio and libm, they could be made of say a dozen parts (even one per
large function) with reduced or enhanced implementations of various
functions, so rom spaced isn't filled with unused code. The default
linking could use a standard stdio or libm. It might not be worth
doing for things that are easily done in C by the user.

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