Bug 14331 - csqrt inaccuracy on internal underflows with subnormal argument
Summary: csqrt inaccuracy on internal underflows with subnormal argument
Status: RESOLVED FIXED
Alias: None
Product: glibc
Classification: Unclassified
Component: math (show other bugs)
Version: 2.16
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
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Blocks:
 
Reported: 2012-07-04 16:55 UTC by Joseph Myers
Modified: 2014-06-18 04:27 UTC (History)
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fweimer: security-

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Description Joseph Myers 2012-07-04 16:55:04 UTC 
Some internal underflows can cause substantial inaccuracy in the results of csqrt.  Specifically, on x86_64, csqrt (0x1p-1074i) returns zero and csqrt (0x1p-500 + 0x1p-1074i) returns an imaginary part of zero (should be 4.469444793151709302716387622440056066334e-249).
Comment 1 Joseph Myers 2012-07-05 11:04:59 UTC 
Fixed for 2.17 by:

commit cdfe2c5eb3703ed964cbfdb6906b21ace2956385
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Jul 5 11:02:13 2012 +0000

    Fix csqrt underflow (bugs 14157, 14331).