[Bug c++/107260] New: The prvalue with the value 0 that is not a integer literal shouldn't convert to std::nullptr_t

[Bug c++/107260] New: The prvalue with the value 0 that is not a integer literal shouldn't convert to std::nullptr_t

[xmh970252187 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107260

            Bug ID: 107260
           Summary: The prvalue with the value 0 that is not a integer
                    literal shouldn't convert to std::nullptr_t
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xmh970252187 at gmail dot com
  Target Milestone: ---

[conv.ptr] p1 says
> A null pointer constant is an integer literal ([lex.icon]) with value zero 

> A null pointer constant of integral type can be converted to a prvalue of type std​::​nullptr_­t.

GCC accept this example
````cpp
std::nullptr_t v = (int)0;
````
However, the initializer expression is not an integer literal, it is a prvalue
of integer type with the value 0. It should be rejected. Clang rejects this
example. https://godbolt.org/z/fxMo4YKE3

[Bug c++/107260] The prvalue with the value 0 that is not a integer literal shouldn't convert to std::nullptr_t

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107260

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-10-14
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to jim x from comment #0)
> GCC accept this example

Well, it does if you include a definition of std::nullptr_t

typedef decltype(nullptr) nullptr_t;
nullptr_t v = (int)0;

Not a regression, this has been accepted since 4.6.4

[Bug c++/107260] The prvalue with the value 0 that is not a integer literal shouldn't convert to std::nullptr_t

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107260

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

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

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I think this is CWG 903 and thus a dup of bug 52145.  The problem here is
probably the same as I described in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77712#c2.

[Bug c++/107260] The prvalue with the value 0 that is not a integer literal shouldn't convert to std::nullptr_t

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107260

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I wonder if we could wrap the INTEGER_CST in a NOP_EXPR/V_C_E to make it clear
it's not an integer literal.

[Bug c++/107260] The prvalue with the value 0 that is not a integer literal shouldn't convert to std::nullptr_t

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107260

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 52145.

*** This bug has been marked as a duplicate of bug 52145 ***