An error is issued by gcc relative to parsing type-id in a new expression

Question

This program

#include <cstddef>

int main()
{
    const std::size_t N1 = 2;
    const std::size_t N2 = 3;

    int ( **p )[N1] = new ( int ( *[N2] )[N1] );
}

does not compile using the compiler C++ gcc HEAD 10.0.0 20190.

The compiler issues error

prog.cc: In lambda function:
prog.cc:8:40: error: expected '{' before ')' token
    8 |    int ( **p )[N1] = new ( int ( *[N2] )[N1] );
      |                                        ^
prog.cc: In function 'int main()':
prog.cc:8:34: error: no match for 'operator*' (operand type is 'main()::<lambda()>')
    8 |    int ( **p )[N1] = new ( int ( *[N2] )[N1] );
prog.cc:8:47: error: expected type-specifier before ';' token
    8 |    int ( **p )[N1] = new ( int ( *[N2] )[N1] );
      |                                               ^

However the program compiles using clang HEAD 10.0.0.

Is the pointer type-id specification ambiguous or is it indeed a gcc bug?

EDIT: By the way if to remove the outer parentheses like

int ( **p )[N1] = new int ( *[N2] )[N1];

then clang also issues an error referencing a lambda

prog.cc:8:38: error: expected body of lambda expression
   int ( **p )[N1] = new int ( *[N2] )[N1];
                                     ^

Answer 1

As far as I can tell, this is definitely a bug in the newest versions of GCC. Presumably, GCC is attempting to parse the ( int ( *[N2] )[N1] ) part as a new-placement, i.e., a parenthesized expression list. Now int ( is interpreted as a function-style cast, etc.

Per new-expression:

new-expression:
    ::_opt new new-placement_opt new-type-id new-initializer_opt
    ::_opt new new-placement_opt ( type-id ) new-initializer_opt

There is no special disambiguation rule regarding new-placement vs ( type-id ), so the thing should be interpreted as a type-id if it cannot be interpreted as an expression-list.

---

The EDIT part is a syntax error per [expr.new]/4:

[ Note: Parentheses in a new-type-id of a new-expression can have surprising effects. [ Example:

new int(*[10])();               // error

is ill-formed because the binding is

(new int) (*[10])();            // error

Instead, the explicitly parenthesized version of the new operator can be used to create objects of compound types:

new (int (*[10])());

allocates an array of 10 pointers to functions (taking no argument and returning int). — end example ] — end note ]