musl: backport various post-1.1.15 fixes

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

diff --git a/toolchain/musl/patches/054-fix-strtod-and-strtof-rounding-with-many-trailing-zeros.patch b/toolchain/musl/patches/054-fix-strtod-and-strtof-rounding-with-many-trailing-zeros.patch
new file mode 100644 (file)
index 0000000..3d9211c
--- /dev/null
+++ b/toolchain/musl/patches/054-fix-strtod-and-strtof-rounding-with-many-trailing-zeros.patch
@@ -0,0 +1,36 @@
+From d184a09e0529f33d8ddddb8825039133483a2c41 Mon Sep 17 00:00:00 2001
+From: Szabolcs Nagy <nsz@port70.net>
+Date: Sun, 4 Sep 2016 04:46:00 +0200
+Subject: fix strtod and strtof rounding with many trailing zeros
+
+in certain cases excessive trailing zeros could cause incorrect
+rounding from long double to double or float in decfloat.
+
+e.g. in strtof("9444733528689243848704.000000", 0) the argument
+is 0x1.000001p+73, exactly halfway between two representible floats,
+this incorrectly got rounded to 0x1.000002p+73 instead of 0x1p+73,
+but with less trailing 0 the rounding was fine.
+
+the fix makes sure that the z index always points one past the last
+non-zero digit in the base 10^9 representation, this way trailing
+zeros don't affect the rounding logic.
+---
+ src/internal/floatscan.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/src/internal/floatscan.c b/src/internal/floatscan.c
+index eef70df..80305ee 100644
+--- a/src/internal/floatscan.c
++++ b/src/internal/floatscan.c
+@@ -172,6 +172,9 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po
+                       return sign * (long double)x[0] * p10s[rp-10];
+       }
+ 
++      /* Drop trailing zeros */
++      for (; !x[z-1]; z--);
++
+       /* Align radix point to B1B digit boundary */
+       if (rp % 9) {
+               int rpm9 = rp>=0 ? rp%9 : rp%9+9;
+-- 
+cgit v0.11.2