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

[Paolo Carlini <paolo dot carlini at oracle dot com>]

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){})
      ;
  }) {}
};

Paolo.