[Bug c++/60009] New: g++ allows copy-initialization of an array of class type from a non-braced string literal

[Bug c++/60009] New: g++ allows copy-initialization of an array of class type from a non-braced string literal

[ed at catmur dot co.uk]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60009

            Bug ID: 60009
           Summary: g++ allows copy-initialization of an array of class
                    type from a non-braced string literal
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ed at catmur dot co.uk

The following code should be rejected, but is accepted by g++ 4.8.1, in both
C++03 and C++11 mode:

struct s { s(const char *); } a[] = "";

It is rejected by clang++ and MSVC.  Credit:
http://stackoverflow.com/questions/21481462/what-does-this-code-mean-and-why-does-it-work

List-initialization is correctly allowed in the braced-init-list case
(a[]{""}), and correctly disallowed in the parenthesized case (a[]("")).

Giving the array extent (a[2] = "") does not appear to make any difference.

It looks like the extent of the array is being taken from the length of the
string literal (including terminator), with some amusing results:

#include <string>
#include <iostream>
int main() {
  std::string a[] = "hello";
  for (int i = 0; i < sizeof(a)/sizeof(a[0]); ++i) std::cout << a[i] << '\n';
}

outputs:

hello
hello
hello
hello
hello
hello

(6, count 'em).

If an array extent is provided (e.g. std::string a[10] = "hello"), then the
string literal will be used to initialize each element.

[Bug c++/60009] g++ allows copy-initialization of an array of class type from a non-braced string literal

[rs2740 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60009

TC <rs2740 at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rs2740 at gmail dot com

--- Comment #1 from TC <rs2740 at gmail dot com> ---
http://stackoverflow.com/questions/24378882/weird-gcc-array-initialization-behavior
appears to be related.

Minimal example:

struct A { A() { } };
int main() { A a[10] = A(); }

Compiles with GCC 4.6, 4.7, 4.8 and 4.9, in both C++98 and C++11 modes, even
though it shouldn't. However,

struct A { };
int main() { A a[10] = A(); }

does not compile in any of the GCC versions tested.

struct A { A() = default; };
int main() { A a[10] = A(); }

Compiles with GCC 4.9 in C++11 mode; does not compile with 4.6-4.8 in C++ 11
mode, however.

[Bug c++/60009] g++ allows copy-initialization of an array of class type from a non-braced string literal

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60009

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-12-14
                 CC|                            |ville.voutilainen at gmail dot com
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.2, 4.9.1, 5.0

--- Comment #2 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Clang rejects the code.

[Bug c++/60009] g++ allows copy-initialization of an array of class type from a non-braced string literal

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60009

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=84632
         Resolution|---                         |FIXED
   Target Milestone|---                         |7.0
             Status|NEW                         |RESOLVED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed in GCC 7, I cannot figure out which revision fixed it though.

Note r8-7514 fixes the error message though where in GCC 7 would print out some
error messages dealing with no matching of constructors.

[Bug c++/60009] g++ allows copy-initialization of an array of class type from a non-braced string literal

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60009

Patrick Palka <ppalka at gcc dot gnu.org> changed:

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

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #3)
> Fixed in GCC 7, I cannot figure out which revision fixed it though.
> 
> Note r8-7514 fixes the error message though where in GCC 7 would print out
> some error messages dealing with no matching of constructors.

Fixed by r7-7236 FWIW