[Bug c++/57573] New: [C++1y] bogus "taking address of temporary" error

[Bug c++/57573] New: [C++1y] bogus "taking address of temporary" error

[redi at gcc dot gnu.org]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57573

            Bug ID: 57573
           Summary: [C++1y] bogus "taking address of temporary" error
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

struct A { };
struct B { A a; };

void f(A*) { }

template<class T>
void g()
{
  B b;
  f(&(b.a));
}

This compiles OK with -std=c++98 or -std=c++11 but not -std=c++1y:

$ g++11 f.cc -std=c++1y -c
f.cc: In function ‘void g()’:
f.cc:10:10: error: taking address of temporary [-fpermissive]
   f(&(b.a));
          ^

It also compiles OK if g() is not a template.

This causes an error in <mutex> in C++1y mode:

/home/redi/gcc/4.x/include/c++/4.9.0/mutex: In function ‘void
std::call_once(std::once_flag&, _Callable&&, _Args&& ...)’:
/home/redi/gcc/4.x/include/c++/4.9.0/mutex:786:48: error: lvalue required as
unary ‘&’ operand
       int __e = __gthread_once(&(__once._M_once), &__once_proxy);
                                                ^

I don't know why those parentheses are there in <mutex> so they just can be
removed to fix the problem.
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From: "nszabolcs at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/57574] New: -stdÉ9 inline function incorrectly has external linkage with prior static declaration
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idW574

            Bug ID: 57574
           Summary: -stdÉ9 inline function incorrectly has external
                    linkage with prior static declaration
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nszabolcs at gmail dot com

gcc emits incorrect warning for inline function with internal linkage:

$ cat example.c
static int n;
static inline int f(void);
inline int f(void) {return n;}
int g(){return f();}

$ gcc-4.8 -stdÉ9 -c example.c
example.c:3:28: warning: 'n' is static but used in inline function 'f' which is
not static [enabled by default]
 inline int f(void) {return n;}
                            ^
$ nm example.o
         U f
00000000 T g
00000000 b n

according to C99 6.2.2p4 the linkage of an identifier
is determined by the prior declaration
(internal in this case, inline does not change that)

referencing static objects from an inline definition
only violates the constraint in C99 6.7.4p3 if the
function has external linkage
(so the diagnostic is unjustified)

it seems from the warning that gcc thinks that f
is not static, this can break code:
the inline definition of f does not provide an
external definition and if the compiler choose
not to inline then the code has undefined f symbol
if the compiler thinks f has external linkage
(as demonstrated by nm above)

[Bug c++/57573] [C++1y] bogus "taking address of temporary" error

[richard-gccbugzilla at metafoo dot co.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57573

Richard Smith <richard-gccbugzilla at metafoo dot co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |richard-gccbugzilla@metafoo
                   |                            |.co.uk

--- Comment #1 from Richard Smith <richard-gccbugzilla at metafoo dot co.uk> ---
This seems to work with GCC trunk.

[Bug c++/57573] [C++1y] bogus "taking address of temporary" error

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57573

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And with the released 4.9.0 too. We should add the testcase and close it.

[Bug c++/57573] [C++1y] bogus "taking address of temporary" error

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57573

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Agreed, I'm taking care of that.

[Bug c++/57573] [C++1y] bogus "taking address of temporary" error

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57573

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
      Known to work|                            |4.10.0, 4.9.0
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.9.0

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

[Bug c++/57573] [C++1y] bogus "taking address of temporary" error

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57573

--- Comment #4 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> ---
Author: paolo
Date: Thu Jun 26 19:38:36 2014
New Revision: 212052

URL: https://gcc.gnu.org/viewcvs?rev=212052&root=gcc&view=rev
Log:
2014-06-26  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/57573
    * g++.dg/template/pr57573.C: New.

Added:
    trunk/gcc/testsuite/g++.dg/template/pr57573.C
Modified:
    trunk/gcc/testsuite/ChangeLog

[Bug c++/57573] [C++1y] bogus "taking address of temporary" error

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57573

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=60409
      Known to work|4.10.0                      |5.0

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
For the record, it started to fail with:

commit 10c6dc8e3932d33c8e47e6706885d2412b29c069 [r0-122521-g10c6dc8e3932d3]
Author: Jason Merrill
Date:   Fri Mar 29 19:51:36 2013

    cp-tree.h (AUTO_IS_DECLTYPE): New.

            N3582
            * cp-tree.h (AUTO_IS_DECLTYPE): New.
            * parser.c (cp_parser_decltype): Handle decltype(auto).
            (cp_parser_type_id_1): Allow auto without a late-specified
            return in C++1y.
            (cp_parser_primary_expression): Use the return value of
            finish_parenthesized_expr.
            (cp_parser_transaction_expression): Likewise.
            * semantics.c (force_paren_expr): New.
            (finish_parenthesized_expr): Use it.
            * call.c (build_conditional_expr_1): Likewise.
            * pt.c (do_auto_deduction): Handle decltype(auto).
            (tsubst_copy): Handle PAREN_EXPR.
            (tsubst_copy_and_build): Likewise.
            * error.c (dump_expr): Handle PAREN_EXPR.
            * cxx-pretty-print.c (pp_cxx_expression): Likewise.
            * mangle.c (write_expression): Ignore PAREN_EXPR.

            * parser.c (cp_parser_decltype_expr): Split out...
            (cp_parser_decltype): ...from here.

    From-SVN: r197248

That commit also caused an ICE, and then this bug and the ICE were both fixed
by:

commit f9b381b8eb56252e302b88ea4fe89beffc33cf80 [r0-128726-gf9b381b8eb5625]
Author: Jason Merrill
Date:   Wed Mar 5 19:25:37 2014

    re PR c++/60409 ([c++1y] ICE on valid with template function)

            PR c++/60409
            * semantics.c (force_paren_expr): Only add a PAREN_EXPR to a
            dependent expression.

    From-SVN: r208352