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Re: [lmi] 0x0000000000000000 != 0x0000000000000000

From: Vadim Zeitlin
Subject: Re: [lmi] 0x0000000000000000 != 0x0000000000000000
Date: Mon, 22 May 2017 01:35:17 +0200

On Sun, 21 May 2017 22:56:05 +0000 Greg Chicares <address@hidden> wrote:

GC> The patch below [0] seems to construct a 'double' that is bitwise
GC> identical to zero, yet compares unequal to zero. How can this be?

 No idea yet. I'll try to debug this later (i.e. not today I'm afraid)
because I also don't see how can this be possible, so I'd like to look at
the generated code and see what it does.

 Just to avoid wasting time on something you might have already checked,
does this happen only with -O2 or does the problem also exist with -O0?

GC> This outcome is seen only with 64-bit msw (not with 32-bit msw,
GC> and not with 64-bit GNU/Linux).

 I've decided to quickly check it nevertheless and discovered that I
couldn't compile tn_range_test.cpp with gcc6 because of its new
"bool-compare" error. I've applied the attached patch as a quick and
minimal fix, but I didn't test it under MSW yet. At least under Linux it
allows me to build and run the test without errors.


Attachment: 0001-Fix-tn_range_test-compilation-with-gcc6.patch
Description: Text document

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