Re: Undefined behavior in atoi()

[Pascal Cuoq <pascal.cuoq@gmail.com>]

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On Tue, Nov 8, 2011 at 4:44 AM, Rich Felker <dalias@aerifal.cx> wrote:

> On Sun, Nov 06, 2011 at 11:28:41PM +0100, Pascal Cuoq wrote:
>
> > I was looking at implementations for strtod() (long story for another
> time)
>
> It should be noted that the current implementation is not correct.
> There's lots of loss-of-precision.
>

So I have seen, but if it's possible to do better for the objectives of
musl,
I do not know how. David M. Gay's code is efficient but it's not portable,
and the other implementation I found (provided as part of Tcl and Ruby
for instance) is only to a few ULPs too.

I am going to write my own, with multi-precision integers (that I already
rely on for other things). I am hoping that by letting ldexp take care
of denormals and infinites, it will be simple.


> Glad to hear you found the code pleasant, at least that part. Some
> things (like floating point in vfprintf.c) are a bit ugly.. :)
>

I did look at the floating-point part in vfprintf.c, because of
the claim on musl's website that printing floating-point numbers
was correct. I have had trouble with floating-point
to decimal conversion too, but I cheated a little there by inventing
by own format:

http://blog.frama-c.com/index.php?post/2011/10/29/A-portable-OCaml-function-to-print-floats

Pascal

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