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sfio: correct floating decimal point scaling of fractions (#131)

Browse source 
_sfcvt(), "convert a floating point value to ASCII", did not adjust
for negative decimal place movement as what happens with leading
zeroes. This caused ksh's 'printf %f' formatter to fail to round
floating point values correctly.

src/lib/libast/sfio/sfcvt.c:
- Removed constraint of <1e-8 for doubles by matching what was done
  for long doubles having <.1.
- Corrected a condition when the next power of 10 occurred and that
  new 1 digit was being overwritten by a 0.

 src/cmd/ksh93/tests/math.sh:
- Validate that typeset -E/F formatting matches that of their
  equivalent printf formatting options as well as checking for
  correct float scaling of the fractional parts.
This commit is contained in:
hyenias 2020-09-14 06:15:05 -04:00 • committed by Martijn Dekker
parent 9f2066f146
commit d7c90eadc3
4 changed files with 67 additions and 9 deletions
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25
src/lib/libast/sfio/sfcvt.c
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@ -287,7 +287,7 @@ int format; /* conversion format */
while(sp < ep)
{ /* generate fractional digits */
if(f <= 0.)
if(f <= 0. && *decpt >= 0)
{ /* fill with 0's */
do { *sp++ = '0'; } while(sp < ep);
goto done;
@ -404,7 +404,7 @@ int format; /* conversion format */
}
} while(f >= (double)CVT_DBL_MAXINT);
}
else if(f > 0.0 && f < 1e-8)
else if(f > 0.0 && f < 0.1)
{ /* scale to avoid excessive multiply by 10 below */
v = SF_MAXEXP10-1;
do
@ -459,7 +459,7 @@ int format; /* conversion format */
while(sp < ep)
{ /* generate fractional digits */
if(f <= 0.)
if(f <= 0. && *decpt >= 0)
{ /* fill with 0's */
do { *sp++ = '0'; } while(sp < ep);
goto done;
@ -480,20 +480,29 @@ int format; /* conversion format */
ep = b+1;
else if(ep < endsp)
{ /* round the last digit */
*--sp += 5;
if (!(format&SFFMT_EFORMAT) && *decpt < 0)
sp += *decpt-1;
else
--sp;
*sp += 5;
while(*sp > '9')
{ *sp = '0';
if(sp > b)
{ if(sp > b)
{ *sp = '0';
*--sp += 1;
}
else
{ /* next power of 10 */
{ /* next power of 10 and at beginning */
*sp = '1';
*decpt += 1;
if(!(format&SFFMT_EFORMAT))
{ /* add one more 0 for %f precision */
ep[-1] = '0';
if (sp != &ep[-1])
{ /* prevents overwriting the previous 1 with 0 */
ep[-1] = '0';
}
ep += 1;
}
break;
}
}
}