[Bug c++/101717] New: ICE capturing static member by ref within stateless lambda

[Bug c++/101717] New: ICE capturing static member by ref within stateless lambda

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

            Bug ID: 101717
           Summary: ICE capturing static member by ref within stateless
                    lambda
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://godbolt.org/z/z4d4qhx8j.
```C++
struct x {
  static void f() noexcept { }
  void (*_)() = [] { [&](auto) { f(); }(0); };
};
```

[Bug c++/101717] ICE capturing static member within stateless generic lambda

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Johel Ernesto Guerrero Peña <johelegp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|ICE capturing static member |ICE capturing static member
                   |by ref within stateless     |within stateless generic
                   |lambda                      |lambda

--- Comment #1 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
A bit simpler and a clarification: capturing at all within a generic stateless
lambda. https://godbolt.org/z/q11fT7MM8.
```C++
struct x {
  static void f() { }
  void (*_)() = [] { [=](auto) { f(); }(0); };
};
```

[Bug c++/101717] [12 Regression] ICE capturing static member within stateless generic lambda

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|ICE capturing static member |[12 Regression] ICE
                   |within stateless generic    |capturing static member
                   |lambda                      |within stateless generic
                   |                            |lambda
            Version|11.0                        |12.0
   Target Milestone|---                         |12.0

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, GCC 11.2 compiles it cleanly.  So this is a regression.

[Bug c++/101717] [12 Regression] ICE capturing static member within stateless generic lambda

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-08-02
             Status|UNCONFIRMED                 |NEW

[Bug c++/101717] [12 Regression] ICE capturing static member within stateless generic lambda

[StevenSun2021 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Steven Sun <StevenSun2021 at hotmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |StevenSun2021 at hotmail dot com

--- Comment #3 from Steven Sun <StevenSun2021 at hotmail dot com> ---
This bug is not introduced in GCC 12.

The relevant code fragment is last edited by g:91e534b0d


in `gcc/cp/lambda.c`
```
gcc_checking_assert
(init && (TREE_TYPE (TREE_TYPE (init))
== current_nonlambda_class_type ()));

```

The assertion fails since long ago. (init == 0 in this case)

Before GCC 12, the `gcc_checking_assert` is `(void)0` in release version,
leaving everything fine. Somehow `gcc_checking_assert` starts working now, and
aborts the program.


My insight on the problem:
The program seems never think of a situation "a lambda inside a lambda inside a
NSDMI`. We need to amend the logic here.

"here" means
https://gcc.gnu.org/git?p=gcc.git;a=blob;f=gcc/cp/lambda.c;h=2e9d38bbe832702804ddcaffc4024ce930a74843;hb=refs/heads/master#l755

By the way, does anyone know other magics like g:hash?

[Bug c++/101717] [12 Regression] ICE capturing static member within stateless generic lambda

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Steven Sun from comment #3)
> By the way, does anyone know other magics like g:hash?

rNNNN works for the old Subversion revisions
"PRNNNN" and "bug NNNN" (maybe one more) puts a link to the other bug.
rN-NNNN (and rN-NNNN-HHHHH) works if you know the new scheme of git revisions
(git gcc-descr can find that for you and you can undo them with gcc-undescr)

I think those are all of the ones which we added to bugzilla, everything else
is standard (e.g. comment #0 works).

[Bug c++/101717] [12 Regression] ICE capturing static member within stateless generic lambda

[StevenSun2021 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

--- Comment #5 from Steven Sun <StevenSun2021 at hotmail dot com> ---
(In reply to Andrew Pinski from comment #4)
Thanks!


(In reply to myself from comment #3)

> The program seems never think of a situation "a lambda inside a lambda
> inside a NSDMI`. We need to amend the logic here.


edit to:

The program seems never think of a situation "member function call inside a
generic lambda inside a lambda inside a NSDMI`. We need to amend the logic
here.


-------------------------------------

The direct cause of failure is in g:91e534b0d

```
if (!containing_function && !COMPLETE_TYPE_P (closure))
    /* If we're parsing a lambda in a non-local class,
       we can find the fake 'this' in scope_chain.  */
    init = scope_chain->x_current_class_ptr;
```

This part of logic is to find the potential `this` since there is a (static)
member function call `f`. Refer to the following comments:

  /* For the overload resolution we need to find the actual `this`
     that would be captured if the call turns out to be to a
     non-static member function.  Do not actually capture it at this
     point.  */


// in function `build_new_method_call_1` in `gcc/cp/call.c`

-------------------------------------

As for example in comment 1:


`scope_chain->x_current_class_ptr` is correctly set when parsing 

```
[=](auto) { f(); }
```

But it was soon incorrectly set when instantiating the same lambda, i.e.
parsing

```
[=](auto) { f(); }()
``` 


This failure only affectes the potential `this` pointer inside the

```
[=](auto) { f(); }
```

But since here needs no `this` pointer, deleting that problematical
`gcc_checking_assert` is actually a potential fix for this problem.

[Bug c++/101717] [9/10/11/12 Regression] ICE capturing static member within stateless generic lambda

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2021-08-02 00:00:00         |2021-12-28
   Target Milestone|12.0                        |9.5
           Keywords|                            |ice-checking,
                   |                            |needs-bisection
            Summary|[12 Regression] ICE         |[9/10/11/12 Regression] ICE
                   |capturing static member     |capturing static member
                   |within stateless generic    |within stateless generic
                   |lambda                      |lambda

[Bug c++/101717] [9/10/11/12 Regression] ICE capturing static member within stateless generic lambda

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/101717] [9/10/11/12 Regression] ICE capturing static member within stateless generic lambda

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org
           Keywords|needs-bisection             |

--- Comment #6 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r9-279-g86cf10840b6cfbfe.

[Bug c++/101717] [9/10/11/12 Regression] ICE capturing static member within stateless generic lambda

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org

[Bug c++/101717] [9/10/11/12 Regression] ICE capturing static member within stateless generic lambda

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:8e4339f5023286d25c7dfa40b4c88e63b780cfd7

commit r12-8036-g8e4339f5023286d25c7dfa40b4c88e63b780cfd7
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Apr 6 22:20:49 2022 -0400

    c++: nested generic lambda in DMI [PR101717]

    We were already checking COMPLETE_TYPE_P to recognize instantiation of a
    generic lambda, but didn't consider that we might be nested in a
non-generic
    lambda.

            PR c++/101717

    gcc/cp/ChangeLog:

            * lambda.cc (lambda_expr_this_capture): Check all enclosing
            lambdas for completeness.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1y/lambda-generic-this4.C: New test.

[Bug c++/101717] [9/10/11 Regression] ICE capturing static member within stateless generic lambda

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:eea5641912b914f3589ec1ec576a596451180baa

commit r11-9824-geea5641912b914f3589ec1ec576a596451180baa
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Apr 6 22:20:49 2022 -0400

    c++: nested generic lambda in DMI [PR101717]

    We were already checking COMPLETE_TYPE_P to recognize instantiation of a
    generic lambda, but didn't consider that we might be nested in a
non-generic
    lambda.

            PR c++/101717

    gcc/cp/ChangeLog:

            * lambda.c (lambda_expr_this_capture): Check all enclosing
            lambdas for completeness.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1y/lambda-generic-this4.C: New test.

[Bug c++/101717] [9/10 Regression] ICE capturing static member within stateless generic lambda

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:20dc7a2119cc0a4e5ddc4a6899a7350621f05440

commit r10-10721-g20dc7a2119cc0a4e5ddc4a6899a7350621f05440
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Apr 6 22:20:49 2022 -0400

    c++: nested generic lambda in DMI [PR101717]

    We were already checking COMPLETE_TYPE_P to recognize instantiation of a
    generic lambda, but didn't consider that we might be nested in a
non-generic
    lambda.

            PR c++/101717

    gcc/cp/ChangeLog:

            * lambda.c (lambda_expr_this_capture): Check all enclosing
            lambdas for completeness.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1y/lambda-generic-this4.C: New test.

[Bug c++/101717] [9 Regression] ICE capturing static member within stateless generic lambda

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:7ce3d2ab2a1a144f94a3a9be716fb831cb76603b

commit r9-10168-g7ce3d2ab2a1a144f94a3a9be716fb831cb76603b
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Apr 6 22:20:49 2022 -0400

    c++: nested generic lambda in DMI [PR101717]

    We were already checking COMPLETE_TYPE_P to recognize instantiation of a
    generic lambda, but didn't consider that we might be nested in a
non-generic
    lambda.

            PR c++/101717

    gcc/cp/ChangeLog:

            * lambda.c (lambda_expr_this_capture): Check all enclosing
            lambdas for completeness.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1y/lambda-generic-this4.C: New test.

[Bug c++/101717] [9 Regression] ICE capturing static member within stateless generic lambda

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101717

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #11 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 9.5/10.4/11.3/12.