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Re: warning about type-punned pointer
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From: |
Thomas Maeder |
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Subject: |
Re: warning about type-punned pointer |
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Date: |
Fri, 28 Apr 2006 22:47:58 +0200 |
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User-agent: |
Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Jumbo Shrimp, linux) |
Ulrich Lauther <ulrich.lauther@siemens.com> writes:
> inline bool almost_equal(float a, float b, int maxUlps = 16) {
> if (a == b) return true;
> int intDiff = abs(*(reinterpret_cast<int*>(&a)) -
> *(reinterpret_cast<int*>(&b)));
> return intDiff <= maxUlps;
> }
>
> I get the warning: warning: dereferencing type-punned pointer will
> break strict-aliasing rules
Seems a mild punishment for such an atrocity.
> How can I avoid this? (Using a union would imply unneeded copying af
> a and b).
And undefined behavior again.
What about the straightforward
return fabs(a-b)<maxUlps;
?