Re: [boost] [1.35][functional] gcc-4.2:dereferencing type-punned pointer will break strict-aliasing rules

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-04-18 11:24:43

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On Wednesday 16 April 2008 22:22 pm, Mat Marcus wrote:
> Hi,
>
> In boost 1.35.0 I'm getting many of the following warnings from
> gcc-4.2.0 under cygwin when using boost/functional/hash:
>
> ../boost_libraries/boost/functional/detail/hash_float.hpp: In function
> 'size_t boost::hash_detail::float_hash_impl(float)':

> Is this a boost bug, or a spurious warning? Is there a fix or a sound
> workaround?

It looks like a real bug to me, from glancing at the header.  It's modifying a 
float variable through an integer pointer, which will break badly on gcc with 
optimization turned on, unless -fno-strict-aliasing is used as Roland 
suggested.

- -- 
Frank
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