From 6d10102709df4bc966d2846c1c45cd667e5048e5 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Fri, 18 Aug 2023 23:16:00 +0200 Subject: math: fix ld80 acoshl(x) for x < 0 acosh(x) is nan for x < 1, but x < 0 cases were not handled specially and acoshl gave wrong result for some -0x1p32 < x < -2 values, e.g.: acoshl(-0x1p20) returned -inf, acoshl(-0x1.4p20) returned -0x1.db365758403aa9acp+0L, fixed by checking the sign bit and handling it specially. reported by Paul Zimmermann. --- src/math/acoshl.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/src/math/acoshl.c b/src/math/acoshl.c index 8d4b43f6..943cec17 100644 --- a/src/math/acoshl.c +++ b/src/math/acoshl.c @@ -10,14 +10,18 @@ long double acoshl(long double x) long double acoshl(long double x) { union ldshape u = {x}; - int e = u.i.se & 0x7fff; + int e = u.i.se; if (e < 0x3fff + 1) - /* |x| < 2, invalid if x < 1 or nan */ + /* 0 <= x < 2, invalid if x < 1 */ return log1pl(x-1 + sqrtl((x-1)*(x-1)+2*(x-1))); if (e < 0x3fff + 32) - /* |x| < 0x1p32 */ + /* 2 <= x < 0x1p32 */ return logl(2*x - 1/(x+sqrtl(x*x-1))); + if (e & 0x8000) + /* x < 0 or x = -0, invalid */ + return (x - x) / (x - x); + /* 0x1p32 <= x or nan */ return logl(x) + 0.693147180559945309417232121458176568L; } #elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384 -- cgit 1.4.1