On 08.10.2024 17:30, Sandra Loosemore wrote:
> On 10/8/24 08:12, Jan Beulich wrote:
>> On 19.06.2024 16:01, Jan Beulich wrote:
>>> Present wording has misled people to believe the ?: operator would be
>>> evaluating all three of the involved expressions.
>>>
>>> gcc/
>>>
>>> * doc/extend.texi: Clarify __builtin_choose_expr() similarity to
>>> the ?: operator.
>>
>> Anyone? I don't think I can simply commit this as "trivial" - there's a
>> certain chance that I'm actually wrong here, after all.
>>
>> Thanks, Jan
>>
>>> --- a/gcc/doc/extend.texi
>>> +++ b/gcc/doc/extend.texi
>>> @@ -14962,9 +14962,9 @@ struct {
>>>
>>> This built-in function is analogous to the @samp{? :} operator in C,
>>> except that the expression returned has its type unaltered by promotion
>>> -rules. Also, the built-in function does not evaluate the expression
>>> -that is not chosen. For example, if @var{const_exp} evaluates to
>>> @code{true},
>>> -@var{exp2} is not evaluated even if it has side effects.
>>> +rules. Like the @samp{? :} operator, the built-in function does not
>>> evaluate
>>> +the expression that is not chosen. For example, if @var{const_exp}
>>> evaluates
>>> +to @code{true}, @var{exp2} is not evaluated even if it has side effects.
>>>
>>> This built-in function can return an lvalue if the chosen argument is an
>>> lvalue.
>>
>
> Hmmm, looking at the complete documentation for this built-in, and the
> code, I think I'd go a little farther with fixing up the docs.
>
> Since requiring the first operand to be a constant is also different
> behavior than the ?: operator, it's misleading to state only the return
> type as being different. So I'd rewrite the whole paragraph quoted above:
>
> Like the @samp{? :} operator, the built-in function does not evaluate
> the expression that is not chosen. For example, if @var{const_exp}
> evaluates
> to @code{true}, @var{exp2} is not evaluated even if it has side effects.
> On the other hand, @code{__builtin_choose_expr} differs from @samp{? :}
> in that the first operand must be a compile-time constant, and the other
> operands are not subject to the @samp{? :} type constraints and promotions.
Fine with me; I assume you will then simply put in your version of the
change?
Jan
