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Date: Fri, 26 Nov 2021 06:51:06 +0900
From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: newlib@sourceware.org
Subject: Re: [PATCH] ldtoa: Fix insufficient valid output digits for "%f"
 format.
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On Thu, 25 Nov 2021 15:09:33 +0100
Corinna Vinschen wrote:
> looks good, but I see a potential problem at one point:
> 
> On Nov 25 21:02, Takashi Yano wrote:
> > +   limit now, either ndec (<= NDEC) or NDEC_SML, depending on ndigits. */
> > +  int ndec;
> > +  if (mode == 3) /* %f */
> > +    {
> > +      int expon = (e[NE - 1] & 0x7fff) - (EXONE - 1); /* exponent part */
> > +      /* log2(10) approximately 485/146 */
> > +      ndec = expon * 146 / 485 + ndigits;
> 
> We have targets with sizeof(int) == 2.  If expon is any number up to
> 0x7fff, multiplying it with 146 will overflow.  Using __int32_t for
> expon should be safer.

Thanks for checking. I have just submitted v2 patch fixed.


-- 
Takashi Yano <takashi.yano@nifty.ne.jp>