From: Joseph Myers <joseph@codesourcery.com>
Date: Tue, 6 Oct 2015 15:32:06 +0000 (+0000)
Subject: Fix ldbl-128ibm logl (1) sign of zero result (bug 19077).
X-Git-Tag: glibc-2.23~401
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=31d4459e42d239fb7d9d3f9532fcf580c6812fb3;p=thirdparty%2Fglibc.git

Fix ldbl-128ibm logl (1) sign of zero result (bug 19077).

The ldbl-128ibm implementation of logl produces a zero with the wrong
sign for logl (1) in FE_DOWNWARD mode.  This patch makes it explicitly
return 0.0L in that case, as in e.g. the ldbl-128 implementation.

Tested for powerpc.

	[BZ #19077]
	* sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): Return
	0.0L for argument 1.0L.
---

diff --git a/ChangeLog b/ChangeLog
index 17388a79278..ac4c1d4aba3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2015-10-06  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #19077]
+	* sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): Return
+	0.0L for argument 1.0L.
+
 	[BZ #19076]
 	* sysdeps/ieee754/ldbl-128ibm/s_log1pl.c (__log1pl): Divide by
 	constant 0.0L when computing infinite result.
diff --git a/NEWS b/NEWS
index b93a5dc4e96..e3c0795fe53 100644
--- a/NEWS
+++ b/NEWS
@@ -18,7 +18,7 @@ Version 2.23
   18820, 18823, 18824, 18825, 18857, 18863, 18870, 18872, 18873, 18875,
   18887, 18921, 18951, 18952, 18956, 18961, 18966, 18967, 18969, 18970,
   18977, 18980, 18981, 18985, 19003, 19012, 19016, 19018, 19032, 19046,
-  19049, 19050, 19059, 19071, 19076.
+  19049, 19050, 19059, 19071, 19076, 19077.
 
 * The obsolete header <regexp.h> has been removed.  Programs that require
   this header must be updated to use <regex.h> instead.
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_logl.c b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
index 58d6bc69726..dcac38062c6 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_logl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
@@ -219,6 +219,8 @@ __ieee754_logl(long double x)
   /* On this interval the table is not used due to cancellation error.  */
   if ((x <= 1.0078125L) && (x >= 0.9921875L))
     {
+      if (x == 1.0L)
+	return 0.0L;
       z = x - 1.0L;
       k = 64;
       t = 1.0L;