[Bug c++/60608] New: Template argument problem

[Bug c++/60608] New: Template argument problem

[volumedriverteam at cloudfounders dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

            Bug ID: 60608
           Summary: Template argument problem
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: volumedriverteam at cloudfounders dot com

#include <functional>
template<typename... Args>
void
wrapper(void (*f)(Args...),
        Args... args)
{
    f(std::forward<Args...>(args...));
}

void
myfun(int)
{}

void
myfun2(const int)
{}

void
test()
{
    int a = 0;
    wrapper<int>(myfun, a);

    wrapper(myfun, a);

    wrapper<int>(myfun2, a);

    const int b = 0;
    wrapper(myfun2, b);

    wrapper<const int>(myfun2, b);
}
It's not clear why the last line doesn't compile. It doesn't give any problem
on clang. The compiler seems to get the type of myfun2 wrong.

[Bug c++/60608] Template argument problem

[redi at gcc dot gnu.org]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="UTF-8", Size: 4748 bytes --]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-03-21
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to volumedriverteam from comment #0)
> void
> myfun2(const int)

Top-level const is removed from function parameters, so this function is
equivalent to:

  void myfun2(int);

And the instantiation wrapper<const int> is equivalent to:

  template<> void wrapper<const int>(void (*)(int), int);

G++ gets confused trying to match const int to int somewhere.


f.cc: In function ‘void test()’:
f.cc:31:33: error: no matching function for call to ‘wrapper(void (&)(int),
const int&)’
     wrapper<const int>(myfun2, b);
                                 ^
f.cc:31:33: note: candidate is:
f.cc:4:1: note: template<class ... Args> void wrapper(void (*)(Args ...), Args
...)
 wrapper(void (*f)(Args...),
 ^
f.cc:4:1: note:   template argument deduction/substitution failed:
f.cc:31:33: note:   mismatched types ‘const int’ and ‘int’
     wrapper<const int>(myfun2, b);
                                 ^
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From: "doko at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/60609] New: [4.8/4.9 Regression] Error: value of 256 too large for field of 1 bytes at 68242
Date: Fri, 21 Mar 2014 12:35:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`609

            Bug ID: 60609
           Summary: [4.8/4.9 Regression] Error: value of 256 too large for
                    field of 1 bytes at 68242
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: doko at gcc dot gnu.org

Created attachment 32416
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id2416&actioníit
preprocessed source

originall reported as a gas issue:
https://sourceware.org/bugzilla/show_bug.cgi?id\x16735

seen when building the ppl 1.1 bindings for SWI Prolog, using binutils from the
2.24 branch on arm-linux-gnueabihf with a compiler defaulting to thumb mode.

seen with current 4.8 branch and at least trunk 20140306.

$ g++ -c -g -O2 ppl_prolog_common.ii
/tmp/ccuRxr3p.s: Assembler messages:
/tmp/ccuRxr3p.s:126688: Error: value of 256 too large for field of 1 bytes at
68242

$ g++ -marm -c -g -O2 ppl_prolog_common.ii
<succeeds>

$ as -v -march=armv7-a -mfloat-abi=hard -mfpu=vfpv3-d16 -meabi=5 -o
ppl_prolog_common.o ppl_prolog_common.s
GNU assembler version 2.24 (arm-linux-gnueabihf) using BFD version (GNU
Binutils for Debian) 2.24
ppl_prolog_common.s: Assembler messages:
ppl_prolog_common.s:130339: Error: value of 256 too large for field of 1 bytes
at 70430

[Bug c++/60608] Template argument problem

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|volumedriverteam@cloudfound |
                   |ers.com                     |

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Thus boils down to:

template<typename... Args>
void
wrapper(void (*f)(Args...), Args...);

void myfun(int);

void
test()
{
  const int b = 0;
  wrapper<const int>(myfun, b);
}

where a non-variadic version is fine. Figuring out where the cv-qualifier is
treated differently in the two cases should be relatively easy...

[Bug c++/60608] Template argument problem

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Slightly shorter:

template<typename... Args>
void
wrapper(void (*f)(Args...));

void myfun(int);

void
test()
{
  wrapper<const int>(myfun);
}

[Bug c++/60608] Template argument problem

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
I'm going to save some debugging notes, mostly about non-variadic vs variadic.

First one: the tsubst in fn_type_unification:

      fntype = tsubst (TREE_TYPE (fn), explicit_targs,
               complain | tf_partial, NULL_TREE);

working on TREE_TYPE (fn) which has uses_template_parms true, returns a fntype
which has uses_template_parms false in the non-variadic case, still true in the
variadic case. Note that later uses_template_parms matters at the beginning of
unify_one_argument.

[Bug c++/60608] Template argument problem

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

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
   Target Milestone|---                         |4.10.0

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

[Bug c++/60608] Template argument problem

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.0                         |5.2

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 5.1 has been released.

[Bug c++/60608] Template argument problem

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.2                         |5.3

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 5.2 is being released, adjusting target milestone to 5.3.

[Bug c++/60608] Template argument problem

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60608

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 111662 has been marked as a duplicate of this bug. ***