[Bug c++/53166] New: static_assert produces bogus warning

[Bug c++/53166] New: static_assert produces bogus warning

[andyg1001 at hotmail dot co.uk]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53166

             Bug #: 53166
           Summary: static_assert produces bogus warning
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: andyg1001@hotmail.co.uk


The following code produces a bogus compilation warning:


template <typename X, X a>
struct A {
    static_assert(a != nullptr, "oops");
};

int a1;
A<int*, &a1> a2;     // this produces a bogus warning
A<int*, nullptr> a3; // correctly generates static assertion


The bogus warning is for the declaration of "a2" saying "the address of ‘a1’
will never be NULL".  This is, of course, true but is exactly what the
static_assert is intended to ensure! (cf. the declaration of "a3").  Here is
the output from gcc:

$ gcc-4.7 -c --std=c++11 bugreport.cpp -Wall -Werror
bugreport.cpp: In instantiation of ‘struct A<int*, (& a1)>’:
bugreport.cpp:7:14:   required from here
bugreport.cpp:2:10: error: the address of ‘a1’ will never be NULL
[-Werror=address]
bugreport.cpp: In instantiation of ‘struct A<int*, 0u>’:
bugreport.cpp:8:18:   required from here
bugreport.cpp:3:5: error: static assertion failed: oops
cc1plus: all warnings being treated as errors

My expectation would be that the static_assert should silently pass, not cause
a warning in this case.  Compare the output that clang gives:

bugreport.cpp:3:5: error: static_assert failed "oops"
    static_assert(a != nullptr, "oops");
    ^             ~~~~~~~~~~~~
bugreport.cpp:8:18: note: in instantiation of template class 'A<int *,
nullptr>' requested here                                     
A<int*, nullptr> a3; // correctly generates static assertion
                 ^
1 error generated.

[Bug c++/53166] static_assert produces bogus warning

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53166

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-04-30
     Ever Confirmed|0                           |1
           Severity|major                       |normal

[Bug c++/53166] static_assert produces bogus warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53166

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |paolo.carlini at oracle dot
                   |gnu.org                     |com
   Target Milestone|---                         |4.8.0

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-05-04 01:38:49 UTC ---
Seems easy.

[Bug c++/53166] static_assert produces bogus warning

[paolo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53166

--- Comment #2 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> 2012-05-04 15:02:10 UTC ---
Author: paolo
Date: Fri May  4 15:02:05 2012
New Revision: 187165

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=187165
Log:
/cp
2012-05-04  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/53166
    * pt.c (instantiate_class_template_1): Increase / decrease
    c_inhibit_evaluation_warnings around the tsubst_expr call
    for STATIC_ASSERT_CONDITION.
    (tsubst_expr, case STATIC_ASSERT): Likewise.
    * typeck.c (cp_build_binary_op, case EQ_EXPR/NE_EXPR): Check
    c_inhibit_evaluation_warnings in the OPT_Waddress warnings.

/testsuite
2012-05-04  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/53166
    * g++.dg/cpp0x/static_assert7.C: New.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/static_assert7.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/cp/typeck.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/53166] static_assert produces bogus warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53166

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-05-04 15:03:17 UTC ---
Fixed for 4.8.0.