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authorSzabolcs Nagy <nsz@port70.net>2012-11-13 10:55:35 +0100
committerSzabolcs Nagy <nsz@port70.net>2012-11-13 10:55:35 +0100
commitc4359e01303da2755fe7e8033826b132eb3659b1 (patch)
tree93cdddff4278c4f0b092ed001f235051a1cd1a72 /src/math/scalbn.c
parent666271c105e4137bdfa195e217799d74143370d4 (diff)
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math: excess precision fix modf, modff, scalbn, scalbnf
old code was correct only if the result was stored (without the excess precision) or musl was compiled with -ffloat-store. now we use STRICT_ASSIGN to work around the issue. (see note 160 in c11 section 6.8.6.4)
Diffstat (limited to 'src/math/scalbn.c')
-rw-r--r--src/math/scalbn.c14
1 files changed, 6 insertions, 8 deletions
diff --git a/src/math/scalbn.c b/src/math/scalbn.c
index 42a2b294..003141e3 100644
--- a/src/math/scalbn.c
+++ b/src/math/scalbn.c
@@ -2,8 +2,6 @@
double scalbn(double x, int n)
{
- /* make sure result is stored as double on overflow or underflow */
- volatile double z;
double scale;
if (n > 1023) {
@@ -13,8 +11,8 @@ double scalbn(double x, int n)
x *= 0x1p1023;
n -= 1023;
if (n > 1023) {
- z = x * 0x1p1023;
- return z;
+ STRICT_ASSIGN(double, x, x * 0x1p1023);
+ return x;
}
}
} else if (n < -1022) {
@@ -24,12 +22,12 @@ double scalbn(double x, int n)
x *= 0x1p-1022;
n += 1022;
if (n < -1022) {
- z = x * 0x1p-1022;
- return z;
+ STRICT_ASSIGN(double, x, x * 0x1p-1022);
+ return x;
}
}
}
INSERT_WORDS(scale, (uint32_t)(0x3ff+n)<<20, 0);
- z = x * scale;
- return z;
+ STRICT_ASSIGN(double, x, x * scale);
+ return x;
}