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37 lines
1.3 KiB
Diff
37 lines
1.3 KiB
Diff
From d184a09e0529f33d8ddddb8825039133483a2c41 Mon Sep 17 00:00:00 2001
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From: Szabolcs Nagy <nsz@port70.net>
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Date: Sun, 4 Sep 2016 04:46:00 +0200
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Subject: fix strtod and strtof rounding with many trailing zeros
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in certain cases excessive trailing zeros could cause incorrect
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rounding from long double to double or float in decfloat.
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e.g. in strtof("9444733528689243848704.000000", 0) the argument
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is 0x1.000001p+73, exactly halfway between two representible floats,
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this incorrectly got rounded to 0x1.000002p+73 instead of 0x1p+73,
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but with less trailing 0 the rounding was fine.
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the fix makes sure that the z index always points one past the last
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non-zero digit in the base 10^9 representation, this way trailing
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zeros don't affect the rounding logic.
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---
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src/internal/floatscan.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/src/internal/floatscan.c b/src/internal/floatscan.c
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index eef70df..80305ee 100644
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--- a/src/internal/floatscan.c
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+++ b/src/internal/floatscan.c
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@@ -172,6 +172,9 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po
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return sign * (long double)x[0] * p10s[rp-10];
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}
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+ /* Drop trailing zeros */
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+ for (; !x[z-1]; z--);
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+
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/* Align radix point to B1B digit boundary */
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if (rp % 9) {
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int rpm9 = rp>=0 ? rp%9 : rp%9+9;
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--
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cgit v0.11.2
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