[Bug c++/61259] New: Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[Bug c++/61259] New: Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[bugs at qult dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

            Bug ID: 61259
           Summary: Spurious "ISO C++ forbids zero-size array" warning
                    with -pedantic
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bugs at qult dot net

The following code, when compiled with -pedantic, compiles properly but
produces a warning about zero-sized array 'argv'.

#include <iostream>

struct Foo {
  Foo(const char* s) : p(s) {}
  const char*    p;
};

int main(int, char* argv[])
{
  const char*    s(Foo(argv[0]).p);
  std::cout << s << std::endl;
  return 0;
}

I understand that const char* s(Foo(argv[0])) is to be understood as being a
declaration of function s taking an array of 0 Foo and returning a const char*,
but with the '.p', apparently the compiler resolves the ambiguity by itself and
the code does build an instance of Foo with argv[0] as an argument.

So in any case, something's wrong: either this code should not compile or it
should not issue the warning.

[Bug c++/61259] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-05-20
      Known to work|                            |4.3.6
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The warning has been given since GCC 4.4 (but not earlier)

[Bug c++/61259] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[ilja.j.honkonen at nasa dot gov]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

ilja.j.honkonen at nasa dot gov changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ilja.j.honkonen at nasa dot gov

--- Comment #2 from ilja.j.honkonen at nasa dot gov ---
I'm seeing this also, when I create an ofstream with () instead of {} I get a
complaint from gcc-4.4 to gcc-5:

#include "vector"
#include "string"
#include "fstream"
#include "boost/filesystem.hpp"
int main() {
        std::vector<std::string> input_files{"a.out"};
        std::ofstream str(
        //std::ofstream str{
                boost::filesystem::path(input_files[0])
                        .parent_path()
                        .append("b")
                        .generic_string()
        );
        //};
}

g++-mp-4.9 gcc.cpp -I $HOME/include -L $HOME/lib -lboost_filesystem
-lboost_system -std=c++0x -W -Wall -Wextra -pedantic -O3
gcc.cpp: In function 'int main()':
gcc.cpp:9:41: warning: ISO C++ forbids zero-size array 'input_files'
[-Wpedantic]
   boost::filesystem::path(input_files[0])
                                         ^

g++-mp-4.4 gcc.cpp -I $HOME/include -L $HOME/lib -lboost_filesystem
-lboost_system -std=c++0x -W -Wall -Wextra -pedantic -O3
gcc.cpp: In function 'int main()':
gcc.cpp:9: warning: ISO C++ forbids zero-size array 'input_files'

[Bug c++/61259] [Regression 8/9/10/11] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[reichelt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

Volker Reichelt <reichelt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |10.3.0, 4.4.0
                 CC|                            |reichelt at gcc dot gnu.org
            Summary|Spurious "ISO C++ forbids   |[Regression 8/9/10/11]
                   |zero-size array" warning    |Spurious "ISO C++ forbids
                   |with -pedantic              |zero-size array" warning
                   |                            |with -pedantic
   Last reconfirmed|2014-05-20 00:00:00         |2021-4-20
           Keywords|                            |rejects-valid

--- Comment #4 from Volker Reichelt <reichelt at gcc dot gnu.org> ---
If you compile the code with "-pedantic-errors" the code is wrongly rejected,
so marking it as rejects-valid.

Self-contained example:

==============================
int foo(int x[2])
{
  int i(int(x[0])*1);
  return i;
}
==============================

[Bug c++/61259] [8/9/10/11/12 Regression] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[Regression 8/9/10/11]      |[8/9/10/11/12 Regression]
                   |Spurious "ISO C++ forbids   |Spurious "ISO C++ forbids
                   |zero-size array" warning    |zero-size array" warning
                   |with -pedantic              |with -pedantic
           Priority|P3                          |P2
   Target Milestone|---                         |8.5

[Bug c++/61259] [9/10/11/12 Regression] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|8.5                         |9.4

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 8 branch is being closed.

[Bug c++/61259] [9/10/11/12 Regression] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.4                         |9.5

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9.4 is being released, retargeting bugs to GCC 9.5.

[Bug c++/61259] [10/11/12/13 Regression] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.5                         |10.4

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9 branch is being closed

[Bug c++/61259] [10/11/12/13 Regression] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.4                        |10.5

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 10.4 is being released, retargeting bugs to GCC 10.5.

[Bug c++/61259] [11/12/13/14 Regression] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.

[Bug c++/61259] [11/12/13/14 Regression] Spurious "ISO C++ forbids zero-size array" warning with -pedantic

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |janschultke at googlemail dot com

--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 114006 has been marked as a duplicate of this bug. ***