64位log10(double)返回10的幂的错误值 [英] 64-bit log10(double) returns wrong values for powers of 10

问题描述

还有其他人看到过这个问题吗?我们有一个基于.Net 2.0的应用程序，该应用程序包含用非托管C ++编写的ActiveX控件，并且看到了在32位Windows上正确运行但在64位Windows上错误运行的情况.我将其跟踪到C ++模块中对log10(double)的调用.有时(在某些情况下，重复)在64位Windows上，log10(1000000.0)返回5.9999999999999991而不是6.0，而log10(10000000.0)返回6.9999999999999991而不是7.0！上下文会触发错误，但它是完全一致的.我们正在使用Visual Studio2008.

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Jon

Has anyone else seen this problem?  We have a .Net 2.0-based application that includes ActiveX controls written in unmanaged C++, and have seen cases that work correctly on 32-bit Windows, but incorrectly on 64-bit Windows.  I tracked it down to a call to log10(double) in a C++ module.  Sometimes (repeatably, in certain contexts), on 64-bit Windows, log10(1000000.0) returns 5.9999999999999991 instead of 6.0, and log10(10000000.0) returns 6.9999999999999991 instead of 7.0!

I can't tell specifically what about the context triggers the error, but it is completely consistent.  We're using Visual Studio 2008.

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Jon

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