[Bug libstdc++/59027] New: std::is_signed does not include check for is_arithmetic

[Bug libstdc++/59027] New: std::is_signed does not include check for is_arithmetic

[marc.mutz at kdab dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

            Bug ID: 59027
           Summary: std::is_signed does not include check for
                    is_arithmetic
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marc.mutz at kdab dot com

According to N3797 Table 49, both is_signed and is_unsigned should evaluate to
true_type only if the argument is_arithmetic, too. is_unsigned honours this,
but is_signed doesn't:

  template<typename _Tp,
           bool = is_arithmetic<_Tp>::value>
    struct __is_signed_helper
    : public false_type { };

  template<typename _Tp>
    struct __is_signed_helper<_Tp, true>
    : public integral_constant<bool, _Tp(-1) < _Tp(0)>
    { };

  /// is_signed
  template<typename _Tp>
    struct is_signed
    : public __is_signed_helper<_Tp>::type
    { };

  /// is_unsigned
  template<typename _Tp>
    struct is_unsigned
    : public __and_<is_arithmetic<_Tp>, __not_<is_signed<_Tp>>>::type
    { };

[Bug libstdc++/59027] std::is_signed does not include check for is_arithmetic

[daniel.kruegler at googlemail dot com]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
Can you provide a test that should fail according to your interpretation? I
think you are misreading the code: is_signed delegates to a specialization of
__is_signed_helper. For this template we have a static branch into types where
is_arithmetic doesn't hold (This returns false_type unconditionally) and
another one where this holds. Only in the latter case further performs the
additional expression test.
>From gcc-bugs-return-433826-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Nov 07 11:52:41 2013
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Subject: [Bug sanitizer/58994] asan.exp regressions on x86_64 darwin at -m64 but not -m32 at r204372
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idX994

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-11-07
     Ever confirmed|0                           |1

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Confirmed on x86_64-apple-darwin13.

Revision 204368 says

Author:    kcc
Date:    Mon Nov 4 21:33:31 2013 UTC (2 days, 14 hours ago)
Log Message:
libsanitizer merge from upstream r191666

** This may break gcc-asan on Mac, will follow up separately. **

The failures are of the kind:

=p739=­dressSanitizer CHECK failed:
../../../../_clean/libsanitizer/sanitizer_common/sanitizer_mac.cc:146
"((env_ptr)) != (0)" (0x0, 0x0)

[Bug libstdc++/59027] std::is_signed does not include check for is_arithmetic

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Marc Mutz from comment #0)
> 
>   template<typename _Tp,
>            bool = is_arithmetic<_Tp>::value>
                    ^^^^^^^^^^^^^^^^^^

>     struct __is_signed_helper
>     : public false_type { };
> 
>   template<typename _Tp>
>     struct __is_signed_helper<_Tp, true>
                                     ^^^^
>     : public integral_constant<bool, _Tp(-1) < _Tp(0)>
>     { };

This looks right to me.

[Bug libstdc++/59027] std::is_signed does not include check for is_arithmetic

[marc.mutz at kdab dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

Marc Mutz <marc.mutz at kdab dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |---

--- Comment #3 from Marc Mutz <marc.mutz at kdab dot com> ---
See code posted in http://llvm.org/bugs/show_bug.cgi?id=17834
is_unsigned<MouseButton> fails, !is_signed succeeds. MouseButton is an enum.

[Bug libstdc++/59027] std::is_signed does not include check for is_arithmetic

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Marc Mutz from comment #3)
> See code posted in http://llvm.org/bugs/show_bug.cgi?id=17834
> is_unsigned<MouseButton> fails, !is_signed succeeds. MouseButton is an enum.

The assertion of the following code is required to hold according to the C++
library specification:

//---------------
#include <type_traits>

enum MouseButton {};

static_assert(!std::is_signed<MouseButton>::value, "");
//---------------

MouseButton is no arithmetic type therefore std::is_signed is required to
return false. If you are interested in the sign character of either the
underlying type or the promoted type of MouseButton, you have to perform
different tests, such as

static_assert(!std::is_signed<std::underlying_type<MouseButton>::type>::value,
"");
static_assert(std::is_signed<decltype(+MouseButton())>::value, "");

(The first result is currently unspecified by the standard)
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From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/59039] Undocumented __builtin_longjmp/__builtin_setjmp
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY039

--- Comment #13 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Eric Botcazou from comment #12)
> No, __builtin_longjmp doesn't touch %rdi at all.  Don't worry too much, the
> SJLJ mechanism of the C++ and Ada compilers has been piggybacked on this for
> a couple of decades, this is quite robust.

This is good to hear.  What is each field?  I assume that
the first 3 fields are frame address, resume address and
stack address.  Are the same for all targets?  What are
the maximum number of fields?

[Bug libstdc++/59027] std::is_signed does not include check for is_arithmetic

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Closing again.

[Bug libstdc++/59027] std::is_signed does not include check for is_arithmetic

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Marc Mutz from comment #0)
> According to N3797 Table 49, both is_signed and is_unsigned should evaluate
> to true_type only if the argument is_arithmetic, too. is_unsigned honours
> this, but is_signed doesn't:

Your own code shows this statement to be false. is_signed is false for your
enumeration type, as required. is_unsigned is also false, as required.

The text in your assertion is wrong:
static_assert(!std::is_signed<MouseButton>::value, "Enum should be unsigned");

It is not true that enums should be unsigned, the traits say enums are neither
signed nor unsigned, and that's what GCC does, as required:

#include <type_traits>
enum MouseButton { };
static_assert(!std::is_signed<MouseButton>::value,
              "Enum should be not be signed");
static_assert(!std::is_unsigned<MouseButton>::value,
              "Enum should not be unsigned");