toolchain/musl/patches/054-fix-strtod-and-strtof-rounding-with-many-trailing-zeros.patch

   1 From d184a09e0529f33d8ddddb8825039133483a2c41 Mon Sep 17 00:00:00 2001
   2 From: Szabolcs Nagy <nsz@port70.net>
   3 Date: Sun, 4 Sep 2016 04:46:00 +0200
   4 Subject: fix strtod and strtof rounding with many trailing zeros
   5
   6 in certain cases excessive trailing zeros could cause incorrect
   7 rounding from long double to double or float in decfloat.
   8
   9 e.g. in strtof("9444733528689243848704.000000", 0) the argument
  10 is 0x1.000001p+73, exactly halfway between two representible floats,
  11 this incorrectly got rounded to 0x1.000002p+73 instead of 0x1p+73,
  12 but with less trailing 0 the rounding was fine.
  13
  14 the fix makes sure that the z index always points one past the last
  15 non-zero digit in the base 10^9 representation, this way trailing
  16 zeros don't affect the rounding logic.
  17 ---
  18  src/internal/floatscan.c | 3 +++
  19  1 file changed, 3 insertions(+)
  20
  21 diff --git a/src/internal/floatscan.c b/src/internal/floatscan.c
  22 index eef70df..80305ee 100644
  23 --- a/src/internal/floatscan.c
  24 +++ b/src/internal/floatscan.c
  25 @@ -172,6 +172,9 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po
  26                         return sign * (long double)x[0] * p10s[rp-10];
  27         }
  28
  29 +       /* Drop trailing zeros */
  30 +       for (; !x[z-1]; z--);
  31 +
  32         /* Align radix point to B1B digit boundary */
  33         if (rp % 9) {
  34                 int rpm9 = rp>=0 ? rp%9 : rp%9+9;
  35 --
  36 cgit v0.11.2