On Apr 3, 2013, at 8:20 AM, Jason Merrill <[email protected]> wrote:
> On 05/11/2012 09:00 PM, John McCall wrote:
>> -- diff begin --
>> Empty parameter lists, whether declared as () or conventionally as (void),
>> are encoded with a void parameter specifier (v). Therefore function types
>> always encode at least one parameter type, and function manglings can always
>> be distinguished from data manglings by the presence of the type. Member
>> functions do not encode the types of implicit parameters, either this or the
>> VTT parameter.
>>
>> -A "Y" prefix for the bare function type encodes extern "C". If there are
>> any cv-qualifiers or a ref-qualifier of this, they are encoded at the
>> beginning of the <qualified-name> as described above. This affects only type
>> mangling, since extern "C" function objects have unmangled names.
>> +When mangling a non-static member function name, if there are any
>> cv-qualifiers or a ref-qualifier of this, they are encoded at the beginning
>> of the <qualified-name> as described above. When mangling any other
>> function type, if there are any cv-qualifiers or a ref-qualifier, they are
>> encoded as part of the function type as described below.
>> +
>> +A "Y" prefix for the bare function type encodes extern "C" in
>> implementations which distinguish between function types with "C" and "C++"
>> language linkage. This affects only type mangling, since extern "C" function
>> objects have unmangled names.
>> -- diff end --
>
> We should also clarify whether the modified function type is a substitution
> candidate. That is, given
>
> template <class T, class U> struct A { };
> void f (A<void()const, void()> *){}
>
> whether f is mangled as
>
> _Z1fP1AIKFvvES0_E
> or
> _Z1fP1AIKFvvEFvvEE
>
> G++ currently treats it as a substitution candidate, clang 3.2 does not, and
> EDG 4.4 neither treats it as a substitution candidate nor mangles the 'const'.
>
> I think not treating it as a substitution candidate is most consistent with
> the language rules, and with the mangling rule for pointer to member function
> types.
This was actually covered in my original proposal:
Therefore I propose the following change:
-- diff begin --
- <function-type> ::= F [Y] <bare-function-type> E
+ <function-type> ::= [<CV-qualifiers>] F [Y] <bare-function-type>
[<ref-qualifier>] E
<bare-function-type> ::= <signature type>+
# types are possible return type, then parameter types
+For the purposes of substitution, the CV-qualifiers and ref-qualifier of a
function type are an indivisible part of the type; that is, when mangling
'void () const', 'void ()' is not a substitution candidate.
-- diff end --
> Incidentally, the change above hasn't been applied to the published ABI yet.
Thanks! I also noticed that Doug's patch for ref-qualifiers from January 2011
hadn't been committed, so I've done that, too.
John.
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