GNU C Library master sources branch master updated. glibc-2.22-310-g7cda516

[jsm28 at sourceware dot org]

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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=7cda516f5f23772fd37ca3a5e018fca5bf388435

commit 7cda516f5f23772fd37ca3a5e018fca5bf388435
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Sep 30 23:34:59 2015 +0000

    Fix ldbl-128ibm exp10l spurious overflows (bug 16620).
    
    The ldbl-128ibm implementation of exp10l uses a version of log(10)
    split into high and low parts - but the low part is negative, so
    causing spurious overflows from __ieee754_expl (exp_high) in cases
    close to the overflow threshold (I added relevant tests close to the
    overflow threshold to the testsuite earlier today).  The same issue
    applies close to the underflow threshold as well (except that spurious
    underflows in IBM long double arithmetic are harder to fix than the
    other deficiencies, so we might end up permitting those for IBM long
    double in the libm testsuite, as permitted by ISO C).
    
    This patch fixes it to use a low part rounded downward to 48 bits
    instead.  (The choice of 48 instead of 53 bits is to make it more
    obviously safe even when the low part of the argument is negative.)
    
    Tested for powerpc.  (Note that because of libgcc bugs with
    multiplication very close to LDBL_MAX, libgcc also needs patching for
    all the problem cases to be fixed, but this patch is still safe and
    correct in the absence of such libgcc fixes.)
    
    	[BZ #16620]
    	* sysdeps/ieee754/ldbl-128ibm/e_exp10l.c (log10_high): Use value
    	of log (10) rounded downward to 48 bits.
    	(log10_low): Use corresponding low part of log (10).

diff --git a/ChangeLog b/ChangeLog
index 958b4a3..a88defa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2015-09-30  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #16620]
+	* sysdeps/ieee754/ldbl-128ibm/e_exp10l.c (log10_high): Use value
+	of log (10) rounded downward to 48 bits.
+	(log10_low): Use corresponding low part of log (10).
+
 	[BZ #19032]
 	* sysdeps/i386/fpu/e_acosh.S (__ieee754_acosh): For arguments < 1,
 	compute result as (x - x) / (x - x) not as 0 / 0.
diff --git a/NEWS b/NEWS
index e7e11bf..06df4b2 100644
--- a/NEWS
+++ b/NEWS
@@ -10,14 +10,14 @@ Version 2.23
 * The following bugs are resolved with this release:
 
   2542, 2543, 2558, 2898, 4404, 6803, 14341, 14912, 15367, 15384, 15786,
-  15918, 16141, 16296, 16415, 16517, 16519, 16520, 16521, 16734, 16973,
-  16985, 17118, 17243, 17244, 17250, 17441, 17787, 17886, 17887, 17905,
-  18084, 18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595, 18610,
-  18618, 18647, 18661, 18674, 18675, 18681, 18757, 18778, 18781, 18787,
-  18789, 18790, 18795, 18796, 18803, 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,
-  19016, 19032.
+  15918, 16141, 16296, 16415, 16517, 16519, 16520, 16521, 16620, 16734,
+  16973, 16985, 17118, 17243, 17244, 17250, 17441, 17787, 17886, 17887,
+  17905, 18084, 18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595,
+  18610, 18618, 18647, 18661, 18674, 18675, 18681, 18757, 18778, 18781,
+  18787, 18789, 18790, 18795, 18796, 18803, 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, 19016, 19032.
 
 * 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_exp10l.c b/sysdeps/ieee754/ldbl-128ibm/e_exp10l.c
index deefe7f..e1f0cbb 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_exp10l.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_exp10l.c
@@ -19,8 +19,8 @@
 #include <math_private.h>
 #include <float.h>
 
-static const long double log10_high = 0x2.4d763776aaa2cp0L;
-static const long double log10_low = -0xf.a456a4a751f4b3d75c75c04c18p-56L;
+static const long double log10_high = 0x2.4d763776aaap+0L;
+static const long double log10_low = 0x2.b05ba95b58ae0b4c28a38a3fb4p-48L;
 
 long double
 __ieee754_exp10l (long double arg)

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                              |    5 +++++
 NEWS                                   |   16 ++++++++--------
 sysdeps/ieee754/ldbl-128ibm/e_exp10l.c |    4 ++--
 3 files changed, 15 insertions(+), 10 deletions(-)


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