Improve documentation of -std option for C++

[Jonathan Wakely]

On 13/01/16 12:54 -0700, Sandra Loosemore wrote:
>On 01/13/2016 12:25 PM, Jonathan Wakely wrote:
>>On 13/01/16 09:53 -0700, Sandra Loosemore wrote:
>>>[snip]
>>>Thanks for doing this.  I have a one big question not addressed by
>>>your patch, and few nit-picky tech-writerish comments.
>>>
>>>The big question is: the existing text in standards.texi says that
>>>"GCC implements the majority of C++98 (@code{export} is a notable
>>>exception) and most of the changes in C++03."  Is it still the case
>>>that there are unimplemented language features from these older
>>>versions of the standard?  If so, is there a detailed list anywhere of
>>>what features are not supported, as there is for the C++11 feature
>>>status?
>>
>>The 'export' feature is definitely still not implemented, and never
>>will be.
>>
>>The only other missing C++03 feature I can think of is
>>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=2316
>>
>>Jason?
>
>Hmmm, it seems like we ought to have a complete list of known 
>unimplemented features, but if there's nothing to link to here at the 
>present time, then don't hold up the rest of the patch for that 
>reason.

The 'export' feature was removed from the standard and only one
compiler ever supported it. PR2316 is also something that very few
compilers support, and "fixing" the bug would break vast quantities of
code that rely on the bug. Most people don't even realise that the C++
standard requires language linkage to affect function types (I keep
meaning to propose that we drop that from the standard, or make it
implementation defined, to make the standard reflect reality).

If those are the only missing features then the wording quoted above
could be made more precise.

>The patch is OK with those changes.

Committed, thanks.