Re: [C++ Patch] PR 84588 ("[8 Regression] internal compiler error: Segmentation fault (contains_struct_check())")

[Jason Merrill <jason at redhat dot com>]

On Tue, May 8, 2018 at 1:46 PM, Paolo Carlini <paolo.carlini@oracle.com> wrote:
> Hi,
>
> On 08/05/2018 19:15, Jason Merrill wrote:
>>
>> On Fri, Apr 20, 2018 at 1:46 PM, Paolo Carlini <paolo.carlini@oracle.com>
>> wrote:
>>>
>>> Hi,
>>>
>>> in this error-recovery regression, after sensible diagnostic about "two
>>> or
>>> more data types in declaration..." we get confused, we issue a cryptic -
>>> but useful hint to somebody working on the present bug ;) - "template
>>> definition of non-template" error and we finally crash. I think the issue
>>> here is that we want to use abort_fully_implicit_template as part of the
>>> error recovery done by cp_parser_parameter_declaration_list, when the
>>> loop
>>> is exited early after a cp_parser_parameter_declaration internally called
>>> synthesize_implicit_template_parm. Indeed, if we do that we get the same
>>> error recovery behavior we get for the same testcase modified to not use
>>> an
>>> auto parameter (likewise for related testcases):
>>>
>>> struct a {
>>>    void b() {}
>>>     void c(auto = [] {
>>>      if (a a(int int){})
>>>        ;
>>>    }) {}
>>> };
>>
>> Hmm, the erroneous declaration is within the lambda body, so messing
>> with whether c is a template seems wrong.
>
> I'm sorry, I don't follow: why you think the issue has to do with c? The
> issue happens while we are parsing:
>
>     a a(int auto)
>
> in the original testcase, in particular the parameters. We set
> parser->fully_implicit_function_template_p in
> synthesize_implicit_template_parm, which in turn is called by
> cp_parser_simple_type_specifier when it sees the auto. As I said, we don't
> have the bug for the snippet you quote above, which is identical to that
> attached in the bug but for the auto in the declaration of a:
>
> struct a {
>   void b() {}
>   void c(void (*) () = [] {
>       if (a a(int auto){})
>       ;
>   }) {}
> };

Ah, I was assuming the quoted testcase was the one in the PR.  The patch is OK.

Jason