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fix strtod int optimization in non-nearest rounding mode

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the mid-sized integer optimization relies on lnz set up properly
to mark the last non-zero decimal digit, but this was not done
if the non-zero digit lied outside the KMAX digits of the base
10^9 number representation.

so if the fractional part was a very long list of zeros (>2048*9 on
x86) followed by non-zero digits then the integer optimization could
kick in discarding the tiny non-zero fraction which can mean wrong
result on non-nearest rounding mode.

strtof, strtod and strtold were all affected.
This commit is contained in:
Szabolcs Nagy
2016-09-04 04:51:03 +02:00
committed by Rich Felker
parent d184a09e05
commit 6ffdc4579f
1 changed files with 4 additions and 1 deletions
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5
src/internal/floatscan.c
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@ -110,7 +110,10 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po
gotdig=1; gotdig=1;
} else { } else {
dc++; dc++;
if (c!='0') x[KMAX-4] |= 1; if (c!='0') {
lnz = dc;
x[KMAX-4] |= 1;
}
} }
} }
if (!gotrad) lrp=dc; if (!gotrad) lrp=dc;