Re: [wwwdocs] gcc-13/porting_to.html: Document C++ -fexcess-precision=standard

[Jakub Jelinek via Gcc-patches]

On Thu, Mar 09, 2023 at 08:09:02AM +0100, Gerald Pfeifer wrote:
> I struggled a bit understanding this and so have come up with what I 
> hope is simpler (without changing the meaning).
> 
> What do you think of the change below?

LGTM, thanks.
> 
> diff --git a/htdocs/gcc-13/porting_to.html b/htdocs/gcc-13/porting_to.html
> index 170da096..8a2822ff 100644
> --- a/htdocs/gcc-13/porting_to.html
> +++ b/htdocs/gcc-13/porting_to.html
> @@ -122,12 +122,14 @@ the operand as an lvalue.<br>
>  
>  <h3 id="excess-precision">Excess precision changes</h3>
>  
> -<p>GCC 13 implements in C++ <a href="changes.html#cxx">excess precision 
> support</a>
> -which has been before implemented just in the C front end.  The new behavior 
> is
> -enabled by default in <code>-std=c++</code><em>NN</em> modes and e.g. when
> -<code>FLT_EVAL_METHOD</code> is 1 or 2 affects behavior of floating point
> -constants and expressions.  E.g. for <code>FLT_EVAL_METHOD</code> equal
> -to 2 on ia32:
> +<p>GCC 13 implements <a href="changes.html#cxx">excess precision
> +support</a>, which was implemented just in the C front end
> +before, in C++. The new behavior is enabled by default in
> +<code>-std=c++</code><em>NN</em> modes and when
> +<code>FLT_EVAL_METHOD</code> is 1 or 2 and affects the behavior of
> +floating point constants and expressions.</p>
> +
> +<p>E.g. for <code>FLT_EVAL_METHOD</code> equal to 2 on ia32
>  
>  <pre><code>
>  #include &lt;stdlib.h&gt;
> @@ -139,11 +141,11 @@ will not abort with standard excess precision, because 
> constants and expressions
>  in <code>float</code> or <code>double</code> are evaluated in precision of
>  <code>long double</code> and demoted only on casts or assignments, but will
>  abort with fast excess precision, where whether something is evaluated in
> -precision of <code>long double</code> or not depends on what evaluations are
> -done in the i387 floating point stack or are spilled from it.
> +<code>long double</code> precision depends on what evaluations are
> +done in the i387 floating point stack or are spilled from it.</p>
>  
> -The <code>-fexcess-precision=fast</code> option can be used to request the
> -previous behavior.
> +</p>The <code>-fexcess-precision=fast</code> option can be used to
> +request the previous behavior.</p>
>  
>  <h3 
> id="alloc-rebind">allocator_traits&lt;A&gt;::rebind_alloc&lt;A::value_type&gt;
>  must be A</h3>
>  

        Jakub