[Bug c++/24215] New: pragma interface in included file with same name

[Bug c++/24215] New: pragma interface in included file with same name

[vbato dot bugs at gmail dot com]

If in a .h file you include another file with the same name, but in a different
directory, that contains a #pragma interface, it seems that the #pragma
interface gets extended to the current file, past the end of the included file.

In the following example there are three files:
a.h   : contains the declaration of a class
a.cpp : includes a.h and contains the implementation of the class.
b/a.h : this is included in a.h. It has the same name as a.h, but is in a
different directory. It contains a #pragma interface

When you compile a.cpp, it doesn't create the virtual table for the Test class.
It looks like the '#pragma interface' is extended to a.h, and since it doesn't
find the corresponding '#pragma implementation' it doesn't include the virtual
table for the class in the object file.

Here's the example:

=====
$ cat a.cpp
#include "a.h"

Test::Test(){}

void Test::f(){}

$ cat a.h
#include "b/a.h"

class Test
{
    public:
        Test();
        virtual void f();
};

$ cat b/a.h

#pragma interface "a.h"
===

If you compile a.cpp, the virtual table for class Test is not created in the
object file:

$ g++ a.cpp
$ nm -C a.o
00000020 T Test::f()
00000010 T Test::Test()
00000000 T Test::Test()
         U vtable for Test

If you rename the file a.h to a2.h and change a.cpp accordingly, you get:
$ nm -C a.o
00000020 T Test::f()
00000010 T Test::Test()
00000000 T Test::Test()
00000000 V typeinfo for Test
00000000 V typeinfo name for Test
00000000 V vtable for Test
         U vtable for __cxxabiv1::__class_type_info

Which should be the correct behaviour.


I've seen this since 4.0. It wasn't present in 3.3.
I've tested it both with gcc 4.0.1 and with the latest 4.1 cvs snapshot:

$ g++ -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.1-20051001/configure --prefix=/home/vbato/gcc41
Thread model: posix
gcc version 4.1.0 20051001 (experimental)


-- 
           Summary: pragma interface in included file with same name
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: vbato dot bugs at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24215

[Bug c++/24215] [4.0/4.1 Regression] pragma interface in included file with same name

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2005-10-05 16:27 -------
Confirmed, a regression from 3.4.0.
Was introduced between "3.5.0 20040909" and "4.0.0 20041124".


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mmitchel at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-code
      Known to fail|                            |4.0.0 4.1.0
      Known to work|                            |3.4.0
   Last reconfirmed|0000-00-00 00:00:00         |2005-10-05 16:27:49
               date|                            |
            Summary|pragma interface in included|[4.0/4.1 Regression] pragma
                   |file with same name         |interface in included file
                   |                            |with same name
   Target Milestone|---                         |4.0.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24215

[Bug c++/24215] [4.0/4.1 Regression] pragma interface in included file with same name

[janis187 at us dot ibm dot com]

------- Comment #2 from janis187 at us dot ibm dot com  2005-10-07 17:26 -------
A regression hunt identified this large patch from Zack Weinberg and
Matt Austern:

  http://gcc.gnu.org/ml/gcc-cvs/2004-09/msg00920.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24215

[Bug c++/24215] [4.0/4.1 Regression] pragma interface in included file with same name

[mmitchel at gcc dot gnu dot org]

------- Comment #3 from mmitchel at gcc dot gnu dot org  2005-10-11 06:49 -------
The semantics of #pragma interface are not entirely well-specified in this
case.  However, the documentation does suggest that you use an explicit
subdirectory when you have multiple headers with the same name in different
directories.  Indeed, using:

#pragma interface "b/a.h"

fixes the problem.

Therefore, I'm going to close this as INVALID.


-- 

mmitchel at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24215