about summary refs log tree commit diff
path: root/math/s_catanl.c
diff options
context:
space:
mode:
authorJoseph Myers <joseph@codesourcery.com>2014-04-02 17:41:02 +0000
committerJoseph Myers <joseph@codesourcery.com>2014-04-02 17:41:02 +0000
commita84e78c8b3c4de94b488fdc5321f71feeb99358f (patch)
treeb4e8a63fd2eb10f4598a5af855e6462a9b06767e /math/s_catanl.c
parent6f05bafebac30a389807979f8efbb709f84b486f (diff)
downloadglibc-a84e78c8b3c4de94b488fdc5321f71feeb99358f.tar.gz
glibc-a84e78c8b3c4de94b488fdc5321f71feeb99358f.tar.xz
glibc-a84e78c8b3c4de94b488fdc5321f71feeb99358f.zip
Fix catan, catanh, __ieee754_logf in round-downward mode (bug 16799, bug 16800).
This patch fixes incorrect results from catan and catanh of certain
special inputs in round-downward mode (bug 16799), and incorrect
results of __ieee754_logf (+/-0) in round-downward mode (bug 16800)
that show up through catan/catanh when tested in all rounding modes,
but not directly in the testing for logf because the bug gets hidden
by the wrappers.

Both bugs involve a zero that should be +0 being -0 instead: one
computed as (1-x)*(1+x) in the catan/catanh case, and one as (x-x) in
the logf case.  The fixes ensure positive zero is used.  Testing of
catan and catanh in all rounding modes is duly enabled.

I expect there are various other bugs in special cases in __ieee754_*
functions that are normally hidden by the wrappers but would show up
for testing with -lieee (or in future with -fno-math-errno if we
replace -lieee and _LIB_VERSION with compile-time redirection to new
*_noerrno symbol names).

Tested x86_64 and x86 and ulps updated accordingly.

	[BZ #16799]
	[BZ #16800]
	* math/s_catan.c (__catan): Avoid passing -0 denominator to atan2
	with 0 numerator.
	* math/s_catanf.c (__catanf): Likewise.
	* math/s_catanh.c (__catanh): Likewise.
	* math/s_catanhf.c (__catanhf): Likewise.
	* math/s_catanhl.c (__catanhl): Likewise.
	* math/s_catanl.c (__catanl): Likewise.
	* sysdeps/ieee754/flt-32/e_logf.c (__ieee754_logf): Always divide
	by positive zero when computing -Inf result.
	* math/libm-test.inc (catan_test): Use ALL_RM_TEST.
	(catanh_test): Likewise.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
Diffstat (limited to 'math/s_catanl.c')
-rw-r--r--math/s_catanl.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/math/s_catanl.c b/math/s_catanl.c
index cea9282a54..dd01d16dcd 100644
--- a/math/s_catanl.c
+++ b/math/s_catanl.c
@@ -97,7 +97,11 @@ __catanl (__complex__ long double x)
 	    }
 
 	  if (absy < LDBL_EPSILON / 2.0L)
-	    den = (1.0L - absx) * (1.0L + absx);
+	    {
+	      den = (1.0L - absx) * (1.0L + absx);
+	      if (den == -0.0L)
+		den = 0.0L;
+	    }
 	  else if (absx >= 1.0L)
 	    den = (1.0L - absx) * (1.0L + absx) - absy * absy;
 	  else if (absx >= 0.75L || absy >= 0.5L)