Re: sizeof

[Russell Shaw <rjshaw@netspace.net.au>]

On 10/5/22 5:22 pm, Andreas Schwab wrote:
> On Mai 10 2022, Russell Shaw wrote:
> 
>>> Andreas Schwab wrote:
>>> On Mai 09 2022, Russell Shaw wrote:
>>>
>>>> sizeof(int()) should transform to sizeof(int (*)()) according to the C++20
>>>> standard.
>>>
>>> No, see [expr.sizeof] #3.
>>
>> What does "[expr.sizeof] #3" refer to ?
> 
> Paragrph #3 in section [expr.sizeof].
> 
>      "The lvalue-to-rvalue (7.3.1), array-to-pointer (7.3.2), and
>      function-to-pointer (7.3.3) standard conversions are not applied to
>      the operand of sizeof."

"Standard conversions" are only applied to expressions, not type-id (which is an 
abstract declarator syntax).

7.6.2.5 Sizeof [expr.sizeof]
3) only applies to the first case "sizeof unary-expression", not the second 
"sizeof ( type-id )".

unary-expression :
   ...
   sizeof unary-expression
   sizeof ( type-id )


**************
7.6.2.5 Sizeof [expr.sizeof]
3)
  The lvalue-to-rvalue (7.3.2), array-to-pointer (7.3.3), and 
function-to-pointer (7.3.4) standard conversions are not applied to the operand 
of sizeof. If the operand is a prvalue, the temporary materialization conversion 
(7.3.5) is applied.

**************
7.3 Standard conversions [conv]
7.3.1 General [conv.general]

A standard conversion sequence will be applied to an expression if necessary to 
convert it to a required destination type.
**************

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