This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: gdb 8.x - g++ 7.x compatibility
On 5 February 2018 at 09:16, Stephan Bergmann wrote:
> On 05.02.2018 06:06, Simon Marchi wrote:
>>
>> On 2018-02-04 02:17 PM, Martin Sebor wrote:
>>>
>>> Printing the suffix is unhelpful because it leads to unnecessary
>>> differences in diagnostics (even in non-template contexts). For
>>> templates with non-type template parameters there is no difference
>>> between, say A<1>, A<1U>, A<(unsigned) 1>, or even A<Green> when
>>> Green is an enumerator that evaluates to 1, so including the suffix
>>> serves no useful purpose.
>>
>>
>> This is the part I don't understand. In Roman's example, spelling
>> foo<10> and foo<10u> resulted in two different instantiations of the
>> template, with different code. So that means it can make a difference,
>> can't it?
>
>
> Yes, for non-type template parameters whose type contains a placeholder type
> (i.e., "auto IVAL" in the earlier example), which is a new feature of C++17.
Right, for C++14 saying foo<2> is entirely unambiguous because the
type of the template parameter is fixed. For C++17 a template declared
as "template<auto> class foo" can be instantiated with different
types, so foo<2> and foo<2u> don't refer to the same specialiation.
> My understanding is that printing the suffix would be essential in such
> cases.
Not sufficient, it doesn't help distinguish foo<(short)2>, foo<(int)2>
or foo<(signed char)2> because there is no suffix for signed/unsigned
short or signed/unsigned char.