Re: [C++ Patch] PR 67065 ("Missing diagnostics for ill-formed program with main variable instead of function")

[Paolo Carlini <paolo.carlini@oracle.com>]

Hi,

On 08/19/2015 10:33 PM, Ville Voutilainen wrote:
> On 19 August 2015 at 23:26, Paolo Carlini <paolo.carlini@oracle.com> wrote:
>> Hi Ville,
>>
>>
>> On 08/19/2015 10:12 PM, Ville Voutilainen wrote:
>>>> submitter noticed that, in violation of [basic.start.main], we don't
>>>> reject
>>>> as ill-formed the declaration of a 'main' variable in the global
>>>> namespace.
>>>> Not a big deal IMHO, but the below simple check works well for me on
>>>> x86_64-linux.
>>> Just fyi, gcc accepts
>>>
>>> decltype(main) x;
>>>
>>> decltype(sizeof(decltype(main)*)) x;
>>>
>>> which are "uses" of main and also violate [basic.start.main]/3.
>> "good" to know. In my experience sometimes the front end appears to
>> so-to-speak pre-declare entities. For instance I filed a while ago
>> c++/48396. Not sure if in practice the exact same code is involved...
> Let me clarify: this is not about that. It's code like
>
> int main() {}
>
> decltype(main) x;
>
> whereas just having
>
> decltype(main) x;
>
> as the whole program will diagnose the use of an undeclared
> identifier. Nevertheless,
> no use, not just odr-use, but use of main as in the entry point
> pseudo-function is allowed
> by the standard, but gcc allows some of them. gcc rejects attempts to
> call main even in
> such decltype contexts, but it can be fooled to allow other uses of main.
Ah, Ok, I didn't actually try to compile your snippet. Then I suspect 
you mean c++/66606?!? Please double check if something is missing in 
Martin's bug!

Paolo.