[Bug c++/33616] New: "lvalue required as unary '&' operand" with template pmf

[Bug c++/33616] New: "lvalue required as unary '&' operand" with template pmf

[mdorey at bluearc dot com]

devadmin@diesel:/tmp$ cat > non-lvalue-pmf.cpp
struct Receive {
};

struct TcpStats {
    Receive rx;
};

typedef void (Receive::*StatsGatherer)(void);

template <StatsGatherer gatherStats>
void test(TcpStats* tcpStats) {
    (tcpStats->rx.*gatherStats)();
}
devadmin@diesel:/tmp$ g++ -W -Wall -pedantic -g   -c -o non-lvalue-pmf.o non-lv
alue-pmf.cpp
non-lvalue-pmf.cpp: In function ?void test(TcpStats*)?:
non-lvalue-pmf.cpp:12: error: lvalue required as unary '&' operand
devadmin@diesel:/tmp$

If this is indeed a bug then it's a regression between 3.3.6 (Debian
1:3.3.6-15) and Debian 4.2.1-5:

devadmin@diesel:/tmp$ g++-3.3 -W -Wall -pedantic -g   -c -o non-lvalue-pmf.o
non-lvalue-pmf.cpp 
devadmin@diesel:/tmp$ 

The regression, if that's what it is, was before 4.1.3 20070831 (prerelease)
(Debian 4.1.2-16).  The error message was improved between 4.1 and 4.2 but the
same underlying problem is in 4.1.

Various easy and harmless work-arounds are possible, for example, changing the
body of the function to read:

    Receive& rx = tcpStats->rx;
    (rx.*gatherStats)();

I tried to simplify the example further but I've been unable to.  One of the
changes that makes the problem go away is to replace the line:

template <StatsGatherer gatherStats>

With:

StatsGatherer gatherStats;

I don't see why that should affect the "lvalue-ness" of tcpStats->rx but I've
been wrong about such things many times before and I look forward to being
amazed.

Extra parentheses around (tcpStats->rx) don't help, just to save anyone from
looking up the operator precedence tables (which was the first thing I did).


-- 
           Summary: "lvalue required as unary '&' operand" with template pmf
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mdorey at bluearc dot com
 GCC build triplet: x86_64-linux-gnu
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2/4.3 regression] "lvalue required as unary '&' operand" with template pmf

[bangerth at dealii dot org]

------- Comment #1 from bangerth at dealii dot org  2007-10-03 14:48 -------
Confirmed, a regression introduced by the new parser in 3.4.0.

W.


-- 

bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at dealii dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |rejects-valid
      Known to fail|                            |3.4.0 4.0.4 4.1.0 4.2.0
                   |                            |4.3.0
      Known to work|                            |3.3.6
   Last reconfirmed|0000-00-00 00:00:00         |2007-10-03 14:48:18
               date|                            |
            Summary|"lvalue required as unary   |[4.1/4.2/4.3 regression]
                   |'&' operand" with template  |"lvalue required as unary
                   |pmf                         |'&' operand" with template
                   |                            |pmf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2/4.3 regression] "lvalue required as unary '&' operand" with template pmf

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
   Target Milestone|---                         |4.2.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2/4.3 regression] "lvalue required as unary '&' operand" with template pmf

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2/4.3 regression] "lvalue required as unary '&' operand" with template pmf

[mmitchel at gcc dot gnu dot org]

------- Comment #2 from mmitchel at gcc dot gnu dot org  2007-10-09 19:20 -------
Change target milestone to 4.2.3, as 4.2.2 has been released.


-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.2.2                       |4.2.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2/4.3 regression] "lvalue required as unary '&' operand" with template pmf

[jakub at gcc dot gnu dot org]

------- Comment #3 from jakub at gcc dot gnu dot org  2007-10-30 11:56 -------
Testing:
--- gcc/cp/decl2.c.jj 2007-10-28 19:34:13.000000000 +0100
+++ gcc/cp/decl2.c     2007-10-30 12:52:35.000000000 +0100
@@ -3499,9 +3499,9 @@ build_offset_ref_call_from_tree (tree fn
         parameter.  That must be done before the FN is transformed
         because we depend on the form of FN.  */
       args = build_non_dependent_args (args);
+      object = build_non_dependent_expr (object);
       if (TREE_CODE (fn) == DOTSTAR_EXPR)
        object = build_unary_op (ADDR_EXPR, object, 0);
-      object = build_non_dependent_expr (object);
       args = tree_cons (NULL_TREE, object, args);
       /* Now that the arguments are done, transform FN.  */
       fn = build_non_dependent_expr (fn);


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2007-10-03 14:48:18         |2007-10-30 11:56:54
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2/4.3 regression] "lvalue required as unary '&' operand" with template pmf

[jakub at gcc dot gnu dot org]

------- Comment #4 from jakub at gcc dot gnu dot org  2007-10-30 22:38 -------
Subject: Bug 33616

Author: jakub
Date: Tue Oct 30 22:37:53 2007
New Revision: 129784

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=129784
Log:
        PR c++/33616
        * decl2.c (build_offset_ref_call_from_tree): Call
        build_non_dependent_expr on object prior to building ADDR_EXPR from it
        if FN is DOTSTAR_EXPR.

        * g++.dg/template/ptrmem18.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/template/ptrmem18.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/decl2.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2 regression] "lvalue required as unary '&' operand" with template pmf

[jakub at gcc dot gnu dot org]

------- Comment #5 from jakub at gcc dot gnu dot org  2007-10-30 22:41 -------
Fixed so far on the trunk.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|3.4.0 4.0.4 4.1.0 4.2.0     |3.4.0 4.0.4 4.1.0 4.2.0
                   |4.3.0                       |
      Known to work|3.3.6                       |3.3.6 4.3.0
            Summary|[4.1/4.2/4.3 regression]    |[4.1/4.2 regression] "lvalue
                   |"lvalue required as unary   |required as unary '&'
                   |'&' operand" with template  |operand" with template pmf
                   |pmf                         |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2 regression] "lvalue required as unary '&' operand" with template pmf

[jsm28 at gcc dot gnu dot org]

------- Comment #6 from jsm28 at gcc dot gnu dot org  2008-02-01 16:54 -------
4.2.3 is being released now, changing milestones of open bugs to 4.2.4.


-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.2.3                       |4.2.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.1/4.2 regression] "lvalue required as unary '&' operand" with template pmf

[jsm28 at gcc dot gnu dot org]

------- Comment #7 from jsm28 at gcc dot gnu dot org  2008-05-19 20:23 -------
4.2.4 is being released, changing milestones to 4.2.5.


-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.2.4                       |4.2.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.2 regression] "lvalue required as unary '&' operand" with template pmf

[jsm28 at gcc dot gnu dot org]

------- Comment #8 from jsm28 at gcc dot gnu dot org  2008-07-04 22:50 -------
Closing 4.1 branch.


-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.1/4.2 regression] "lvalue|[4.2 regression] "lvalue
                   |required as unary '&'       |required as unary '&'
                   |operand" with template pmf  |operand" with template pmf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616

[Bug c++/33616] [4.2 regression] "lvalue required as unary '&' operand" with template pmf

[jsm28 at gcc dot gnu dot org]

------- Comment #9 from jsm28 at gcc dot gnu dot org  2009-03-30 22:28 -------
Closing 4.2 branch, fixed in 4.3.


-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
      Known to fail|3.4.0 4.0.4 4.1.0 4.2.0     |3.4.0 4.0.4 4.1.0 4.2.0
                   |                            |4.2.5
         Resolution|                            |FIXED
   Target Milestone|4.2.5                       |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33616