[Bug c++/65815] New: std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error

[Bug c++/65815] New: std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error

[andras.aszodi at csf dot ac.at]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

            Bug ID: 65815
           Summary: std::array initialization with initializer list: a =
                    {x,y,z} incorrectly flagged as syntax error
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: andras.aszodi at csf dot ac.at

On Page 975 of "The C++ Programming Language", 4th edition, Bjarne Stroustrup
says:

"An array can be initialized by an initializer list:
array<int,3> a1 = { 1, 2, 3 };"

and Clang (V 3.5) accepts it. However, G++ 4.9.2 thinks this is an error:

"error: array must be initialized with a brace-enclosed initializer
     const std::array<double, 3> _ar0val = {1.0, -1.0, 1.0};"

The ugly fix is:

#ifdef __GNUC__
    const std::array<double, 3> _ar0val{{1.0, -1.0, 1.0}};
#else
    const std::array<double, 3> _ar0val = {1.0, -1.0, 1.0};
#endif

but of course it is still a bug.

[Bug c++/65815] std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

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

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

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Hm?  This compiles just fine for me:

#include <array>
const std::array<double, 3> q1 = {1.0, -1.0, 1.0};
const std::array<double, 3> q2{{1.0, -1.0, 1.0}};

So can you provide a complete test case?

[Bug c++/65815] std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2015-04-20
     Ever confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Works for me, please provide a complete testcase and your exact g++ command.

https://gcc.gnu.org/bugs/

[Bug c++/65815] std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error

[andras.aszodi at csf dot ac.at]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

--- Comment #3 from andras.aszodi at csf dot ac.at ---
(In reply to Marek Polacek from comment #1)
> Hm?  This compiles just fine for me:
> 
> #include <array>
> const std::array<double, 3> q1 = {1.0, -1.0, 1.0};
> const std::array<double, 3> q2{{1.0, -1.0, 1.0}};
> 
> So can you provide a complete test case?

Thanks a lot. Yes, this works for me, too:

#include <array>
#include <iostream>

int main(int argc, char *argv[]) {
  std::array<double, 2> a = {1.0, 2.0};
  std::cout << a[0] << ", " << a[1] << std::endl;
}

The problem manifests itself if the array is a member variable in a class and
initialised "inline". Details in my new comment below.

[Bug c++/65815] std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to andras.aszodi from comment #3)
> The problem manifests itself if the array is a member variable in a class
> and initialised "inline". Details in my new comment below.

There are no details anywhere. Please keep in mind that a complete code example
is generally required for an issue. So, if I understand you correctly, you have
the following code in mind:

//------------------------------
#include <array>

struct X 
{
  std::array<double, 3> q1 = {1.0, -1.0, 1.0}; 
};
//------------------------------

?
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Subject: [Bug c++/65815] std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

--- Comment #5 from andras.aszodi at csf dot ac.at ---
If the array is a class member and it is initialized in-class then the
"single-brace" syntax gets flagged. Please try the following example:

// ----- file clarrinit.cc --
#include <array>
#include <iostream>

class Fred {
  public:
  const std::array<double, 2>& arr() const { return _a; }

  private:
  std::array<double, 2> _a = {1.0, 2.0}, // error
    _b{3.0, 4.0}, // error
    _c{{5.0, 6.0}}; // OK
};

int main(int argc, char *argv[]) {
  Fred f;
  std::cout << f.arr()[0] << std::endl;
}
// ----

Platform: Raspberry Pi 2, OS is Raspbian (not that it should matter IMO)
Command: `g++-4.9 -g -std=c++11 clarrinit.cc -o clarrinit`
Output: 
error: array must be initialized with a brace-enclosed initializer
   std::array<double, 2> _a = {1.0, 2.0},
                                       ^
clarrinit.cc:9:39: error: too many initializers for ‘std::array<double, 2u>’
clarrinit.cc:10:16: error: array must be initialized with a brace-enclosed
initializer
     _b{3.0, 4.0},
                ^
clarrinit.cc:10:16: error: too many initializers for ‘std::array<double, 2u>’
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To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/65815] std::array initialization with initializer list: a = {x,y,z} incorrectly flagged as syntax error
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

--- Comment #6 from andras.aszodi at csf dot ac.at ---
You were too quick, I was too slow... please re-check :-)

(In reply to Daniel Krügler from comment #4)
> (In reply to andras.aszodi from comment #3)
> > The problem manifests itself if the array is a member variable in a class
> > and initialised "inline". Details in my new comment below.
> 
> There are no details anywhere. Please keep in mind that a complete code
> example is generally required for an issue. So, if I understand you
> correctly, you have the following code in mind:
> 
> //------------------------------
> #include <array>
> 
> struct X 
> {
>   std::array<double, 3> q1 = {1.0, -1.0, 1.0}; 
> };
> //------------------------------
> 
> ?
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Subject: [Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

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

--- Comment #16 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---

What is printed with -Wno-error=narrowing ?
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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/65815] brace elision doesn't work in NSDMI
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide815

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|WAITING                     |NEW
            Summary|std::array initialization   |brace elision doesn't work
                   |with initializer list: a =  |in NSDMI
                   |{x,y,z} incorrectly flagged |
                   |as syntax error             |

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced:

struct array {
  int data [2];
};

struct X {
  array a = { 1, 2 };
};

[Bug c++/65815] brace elision doesn't work in NSDMI

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |paolo.carlini at oracle dot com

--- Comment #8 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Mine.

[Bug c++/65815] brace elision doesn't work in NSDMI

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

--- Comment #9 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> ---
Author: paolo
Date: Tue Jun  9 14:59:08 2015
New Revision: 224286

URL: https://gcc.gnu.org/viewcvs?rev=224286&root=gcc&view=rev
Log:
/cp
2015-06-09  Paolo Carlini  <paolo.carlini@oracle.com>

        PR c++/65815
        * typeck2.c (digest_nsdmi_init): On aggregates use reshape_init.
        * init.c (expand_default_init): Likewise.

/testsuite
2015-06-09  Paolo Carlini  <paolo.carlini@oracle.com>

        PR c++/65815
        * g++.dg/cpp0x/nsdmi-aggr1.C: New.
        * g++.dg/cpp0x/mem-init-aggr1.C: Likewise.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/mem-init-aggr1.C
    trunk/gcc/testsuite/g++.dg/cpp0x/nsdmi-aggr1.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/init.c
    trunk/gcc/cp/typeck2.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/65815] brace elision doesn't work in NSDMI

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65815

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
           Assignee|paolo.carlini at oracle dot com    |unassigned at gcc dot gnu.org
   Target Milestone|---                         |6.0

--- Comment #10 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed.