[patch] Fix pr16247

[Richard Smith]

On Mon, Jun 17, 2013 at 11:26 AM, Richard Smith <richard at metafoo.co.uk> wrote:
> On Mon, Jun 17, 2013 at 11:13 AM, Douglas Gregor <dgregor at apple.com> wrote:
>>
>> On Jun 17, 2013, at 11:02 AM, Richard Smith <richard at metafoo.co.uk> wrote:
>>
>> On Mon, Jun 17, 2013 at 9:21 AM, Douglas Gregor <dgregor at apple.com> wrote:
>>
>>
>> On Jun 11, 2013, at 6:02 AM, Rafael Espíndola <rafael.espindola at gmail.com>
>> wrote:
>>
>> On 10 June 2013 19:08, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
>>
>> Richard pointed out on IRC that the patch should look at the
>> redeclaration context to avoid problems with one of the functions
>> being in a extern "C++". Implementing that found some interesting
>> problems. Consider
>>
>> extern "C" {
>> static void foo(int x);
>> static void foo() {
>> }
>> void foo(int x) {
>> }
>> }
>>
>> This should be valid, since both functions have internal linkage and
>> therefore none of them has C language linkage. Commenting the first
>> declaration makes the code invalid as now the last one is extern C and
>> [dcl.link] p6 kicks in. This means we have to do "normal" overload
>> resolution first to see if the last decl we are looking at has C
>> language linkage or not.
>>
>>
>> BTW, is this sufficient evidence that we should just give static
>> functions C language linkage? I just checked http://gcc.godbolt.org/
>> and gcc 4.8 and icc 13 (which is edg based, no?), reject
>>
>> extern "C" {
>> static void foo() {
>> }
>> static void foo(int x) {
>> }
>> }
>>
>> We are putting quiet a bit of effort to make sure we accept it and I
>> still can't see the value.
>>
>>
>> I, too, find this behavior strange. Changing between static and non-static
>> shouldn’t affect whether a function can be overloaded; it’s completely
>> non-intuitive and apparently at odds with existing practice in GCC/EDG.
>>
>>
>> The latter, at least, is not the case; EDG accepts this code in both
>> its compliant mode and in its g++-compatible mode. I'm surprised that
>> ICC rejects this.
>>
>>
>> Ah, interesting. Might be one of the many compatibility knobs that EDG
>> provides.
>>
>> The former makes some degree of sense to me -- a
>> 'static' declaration doesn't have external linkage and thus doesn't
>> have C linkage -- although I agree that it's weird.
>>
>>
>> So existing practice is mixed, with a bias toward rejecting the code above
>> (apparently, MSVC also rejects the code in question). The standard is clear
>> that the code is well-formed, but we find that result to be weird. This is
>> starting to feel like a case where we badger the committee into fixing the
>> standard :)
>
> The committee have been badgered about this before; this was core issue 4:
>
>   http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#4
>
> I'm not sure that anything relevant has changed since, other than gcc
> and MSVC not implementing that DR in the 12 intervening years. I'm
> also not clear on what we would gain by changing this in the standard.

I also badgered the committee back in February when this last came up,
and no consensus for a language change appeared. I'm trying
rebadgering :)