[Webkit-unassigned] [Bug 123624] New: Precision errors in Math.cbrt() on GTK, EFL

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=123624

           Summary: Precision errors in Math.cbrt() on GTK, EFL
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: zandobersek at gmail.com
                CC: oliver at apple.com, gyuyoung.kim at samsung.com,
                    msaboff at apple.com


Math.cbrt(), introduced in r158401, is returning unexpected values in the js/math.html layout test (and the related stress tests) that are indicating precision errors. This only occurs on GTK and EFL.
http://trac.webkit.org/changeset/158401

The precision error originates in the underlying cbrt() call in JSC::mathProtoFuncCbrt. pow() works as expected, FWIW.

Diff:
--- /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/js/math-expected.txt
+++ /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/js/math-actual.txt
@@ -184,8 +184,8 @@
 PASS Math.cbrt(NaN) is NaN
 PASS Math.cbrt(0) is 0
 PASS Math.cbrt(-0) is -0
-PASS Math.cbrt(27) is 3
-PASS Math.cbrt(-27) is -3
+FAIL Math.cbrt(27) should be 3. Was 3.0000000000000004.
+FAIL Math.cbrt(-27) should be -3. Was -3.0000000000000004.
 PASS Math.cbrt(Infinity) is Infinity
 PASS Math.cbrt(-Infinity) is -Infinity
 PASS Math.cosh(NaN) is NaN

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