[Bug c++/110340] New: [C++26] P2621R2 - Remove undefined behavior from lexing

[Bug c++/110340] New: [C++26] P2621R2 - Remove undefined behavior from lexing

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110340

            Bug ID: 110340
           Summary: [C++26] P2621R2 - Remove undefined behavior from
                    lexing
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

See <https://wg21.link/P2621R2>.

[Bug c++/110340] [C++26] P2621R2 - Remove undefined behavior from lexing

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110340

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Full testcase for the first 2 issues raised in the paper:
```
int \\
u\
0\
3\
9\
1 = 0;

#define CONCAT(x,y) x##y

int CONCAT(\,u0393)=0;
```

Testcase for the last one:
```
const char * foo=" // { dg-error "" }
```

as far as I understand from the paper, instead of the above being undefined at
compiletime, the first testcase becomes valid and the last one becomes invalid.
And right now GCC acts according to the paper already so there is not anything
to be done. Maybe add a testcase for these if there is not already one is
enough ...

[Bug c++/110340] [C++26] P2621R2 - Remove undefined behavior from lexing

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110340

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> Full testcase for the first 2 issues raised in the paper:

Thanks, want to add these to the testsuite and close the PR?

[Bug c++/110340] [C++26] P2621R2 - Remove undefined behavior from lexing

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110340

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-06-23
             Status|UNCONFIRMED                 |ASSIGNED

[Bug c++/110340] [C++26] P2621R2 - Remove undefined behavior from lexing

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110340

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:fca089e8a47314a40ad93527ba9f9d0d374b3afb

commit r14-2626-gfca089e8a47314a40ad93527ba9f9d0d374b3afb
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Jul 18 13:26:39 2023 -0400

    c++: Add tests for P2621, no UB in lexer [PR110340]

    C++26 P2621 removes UB in the lexer and either makes the construct valid
    or ill-formed.  We're already handling this correctly so this patch only
    adds tests.

            PR c++/110340

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp/string-4.C: New test.
            * g++.dg/cpp/ucn-2.C: New test.

[Bug c++/110340] [C++26] P2621R2 - Remove undefined behavior from lexing

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110340

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Done.