[Bug c++/29095] New: cxxabi.h __cxa_cdtor_type not declared when included from "C"

[Bug c++/29095] New: cxxabi.h __cxa_cdtor_type not declared when included from "C"

[jaco at kroon dot co dot za]

#ifdef __cplusplus
namespace __cxxabiv1
{
  typedef __cxa_cdtor_return_type (*__cxa_cdtor_type)(void *);

  extern "C"
  {
#endif

  // Allocate array.
  void*
  __cxa_vec_new(size_t __element_count, size_t __element_size,
                size_t __padding_size, __cxa_cdtor_type constructor,
                __cxa_cdtor_type destructor);


When the above snippet from cxxabi.h gets parsed as "C" then __cxa_cdtor_type
won't be defined, the declaration needs to move out of the #ifdef to inside the
extern "C" part.


-- 
           Summary: cxxabi.h __cxa_cdtor_type not declared when included
                    from "C"
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jaco at kroon dot co dot za
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2006-09-15 06:08 -------
Actually we have to becareful here.
What does the IA64 C++ ABI say about the arguments types to __cxa_vec_new, is
__cxa_cdtor_type really extern "C" or did they forget to specify the language
linkage?


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |libstdc++


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-09-15 06:12 -------
(In reply to comment #1)
The other thing is that I think this is a regression from when the ARM eabi
support was added.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[jaco at kroon dot co dot za]

------- Comment #3 from jaco at kroon dot co dot za  2006-09-15 06:21 -------
Ok.  My understanding of CXX ABI isn't that great.  Some would say "I just code
with C/C++" but I also happen to know that that isn't true.  Take what I say
here as "I'm a user of C/C++ and my understanding of everything behind the
scenes may not quite be what it should".

It's a typedef for a function pointer that takes a void* parameter.  Whether we
use it in C/C++ the actual calling semantics should be the same afaik.  aka, we
push the void* onto the stack, and issue the call to the given pointer address.
 The size of the actual pointer should be the same size whether we use C or
C++, so I fail to see how this would make a difference.  The other solution is
to close the #ifdef and re-open it, and that imho will look a lot uglier.  It
won't make a difference to the "C" compiled version (when compared to moving
the typedef), whereas I simply fail to see the difference when compiling as a
"C++" program (if there is any).

As for regression, this worked in 3.4.6, at which point the typedef was absent,
and instead the function pointer signatures was handled inside the function
declarations:

  void*
  __cxa_vec_new(size_t __element_count, size_t __element_size,
                size_t __padding_size, void (*__constructor) (void*),
                void (*__destructor) (void*));


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2006-09-15 16:27 -------
Caused by:
2004-09-15  Mark Mitchell  <mark@codesourcery.com>

        * config/cpu/arm/cxxabi_tweaks.h (__cxa_cdtor_return_type):
        Define.
        * config/cpu/generic/cxxabi_tweaks.h (__cxa_cdtor_return_type):
        Define.
        * libsupc++/cxxabi.h (__cxa_cdtor_return_type): New type.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at codesourcery dot com
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
      Known to fail|                            |4.0.0 4.1.0 4.2.0
      Known to work|                            |3.4.0
   Last reconfirmed|0000-00-00 00:00:00         |2006-09-15 16:27:19
               date|                            |
            Summary|cxxabi.h __cxa_cdtor_type   |[4.0/4.1/4.2 Regression]
                   |not declared when included  |cxxabi.h __cxa_cdtor_type
                   |from "C"                    |not declared when included
                   |                            |from "C"
   Target Milestone|---                         |4.0.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[mmitchel at gcc dot gnu dot org]

------- Comment #5 from mmitchel at gcc dot gnu dot org  2006-09-20 22:49 -------
The language linkage of the type is supposed to matter in some cases -- but G++
doesn't implement that, so I don't think the difference is observable in GNU
C++.  In any case, we should try to make the file compile in C -- or else
remove the #ifdefs -- so, even if we want to keep the C++ linkage for the type,
we should provide a declaration in C mode.


-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[pcarlini at suse dot de]

-- 

pcarlini at suse dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |pcarlini at suse dot de
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[pcarlini at suse dot de]

------- Comment #6 from pcarlini at suse dot de  2006-10-06 11:14 -------
I'm reassigning to Benjamin...


-- 

pcarlini at suse dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|pcarlini at suse dot de     |bkoz at redhat dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[mmitchel at gcc dot gnu dot org]

------- Comment #7 from mmitchel at gcc dot gnu dot org  2006-10-06 19:18 -------
I'm following up to the mailing list in the PR trail, since it's very confusing
to go back and forth between the two.

The technical issue is that in the following code:

  extern "C" {
    typedef void (*p1)();
  }
  typedef void (*p2)();

p1 and p2 are distinct types, and, in fact, you can overload based on that. 
G++ doesn't implement that distinction; we don't keep track of language linkage
for types (just for functions) but we should, and, at some point, I'm sure
we'll implement that.  The reason this is in the standard is so that an
implementation can use different calling conventions for C and C++.  So, when
calling through a function pointer you have to know which kind of function
you're calling.  (And, yes, name-mangling is supposed to encode the linkage of
the function type, when mangling a pointer-to-function type.)

So, changing the linkage of __cxa_cdtor_return_type (that name is not specified
in the ABI, by the way), technically changes the type of __cxa_vec_new.

However, the ABI specification does say that __cxa_vec_new is declared extern
"C", and, since it specifically gives this prototype:

 extern "C" void * __cxa_vec_new (
            size_t element_count,
            size_t element_size,
            size_t padding_size,
            void (*constructor) ( void *this ),
            void (*destructor) ( void *this ) );

that means that the type of the constructor and destructor arguments are also
required to be pointers-to-C-functions.

In summary, I think Benjamin's proposed change (to change the constructor type
to have extern "C" linkage) is in fact required by the ABI.  Although it's
technically a source-incompatible change, since G++ doesn't implement linkage
for function pointers, there's no way that a user of G++ can tell the
difference.  Therefore, I think that's the right thing to do.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[bkoz at gcc dot gnu dot org]

------- Comment #8 from bkoz at gcc dot gnu dot org  2006-10-09 23:53 -------
Subject: Bug 29095

Author: bkoz
Date: Mon Oct  9 23:53:35 2006
New Revision: 117589

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117589
Log:
2006-10-09  Benjamin Kosnik  <bkoz@redhat.com>

        PR libstdc++/29095
        * libsupc++/cxxabi.h (__cxa_cdtor_type): Explicit "C" linkage.
        * config/cpu/arm/cxxabi_tweaks.h: Same.
        * config/cpu/generic/cxxabi_tweaks.h: Same.
        * testsuite/abi: Add.
        * testsuite/abi/header_cxxabi.cc: New.
        * testsuite/demangle: Move...
        * testsuite/abi/demangle: ...here.
        * testsuite/libstdc++-dg/conformance.exp: Adjust testsuite file
        calculation.
        * scripts/create_testsuite_files: Same.
        * testsuite/lib/libstdc++.exp (v3_target_compile_as_c): New.
        (libstdc++-dg-test): Use it.


Added:
    trunk/libstdc++-v3/testsuite/abi/
    trunk/libstdc++-v3/testsuite/abi/demangle/
      - copied from r117575, trunk/libstdc++-v3/testsuite/demangle/
    trunk/libstdc++-v3/testsuite/abi/header_cxxabi.c
Removed:
    trunk/libstdc++-v3/testsuite/demangle/
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/config/cpu/arm/cxxabi_tweaks.h
    trunk/libstdc++-v3/config/cpu/generic/cxxabi_tweaks.h
    trunk/libstdc++-v3/libsupc++/cxxabi.h
    trunk/libstdc++-v3/scripts/create_testsuite_files
    trunk/libstdc++-v3/testsuite/lib/libstdc++.exp
    trunk/libstdc++-v3/testsuite/libstdc++-dg/conformance.exp


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[bkoz at gcc dot gnu dot org]

------- Comment #9 from bkoz at gcc dot gnu dot org  2006-10-11 08:30 -------
Subject: Bug 29095

Author: bkoz
Date: Wed Oct 11 08:30:42 2006
New Revision: 117629

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117629
Log:
2006-10-09  Benjamin Kosnik  <bkoz@redhat.com>

        PR libstdc++/29095
        * libsupc++/cxxabi.h (__cxa_cdtor_type): Explicit "C" linkage.
        * config/cpu/arm/cxxabi_tweaks.h: Same.
        * config/cpu/generic/cxxabi_tweaks.h: Same.


Modified:
    branches/gcc-4_1-branch/libstdc++-v3/ChangeLog
    branches/gcc-4_1-branch/libstdc++-v3/config/cpu/arm/cxxabi_tweaks.h
    branches/gcc-4_1-branch/libstdc++-v3/config/cpu/generic/cxxabi_tweaks.h
    branches/gcc-4_1-branch/libstdc++-v3/libsupc++/cxxabi.h


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[bkoz at gcc dot gnu dot org]

------- Comment #10 from bkoz at gcc dot gnu dot org  2006-10-11 08:33 -------

Fixed in mainline and gcc-4.1.2.


-- 

bkoz at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|4.0.4                       |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[pcarlini at suse dot de]

------- Comment #11 from pcarlini at suse dot de  2006-10-13 16:45 -------
Benjamin, I'm seeing these failures:

  http://gcc.gnu.org/ml/gcc-testresults/2006-10/msg00654.html
  http://gcc.gnu.org/ml/gcc-testresults/2006-10/msg00575.html

Are you sure the patch is ok wrt "source-less" (I don't remember the exact name
of the procedure, sorry) testing (Codesourcery testing, in other terms)?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[bkoz at gcc dot gnu dot org]

------- Comment #12 from bkoz at gcc dot gnu dot org  2006-10-16 14:06 -------

Paolo you are correct, non-build testing is at issue. I'm trying to fix...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095

[Bug libstdc++/29095] [4.0/4.1/4.2 Regression] cxxabi.h __cxa_cdtor_type not declared when included from "C"

[bkoz at gcc dot gnu dot org]

------- Comment #13 from bkoz at gcc dot gnu dot org  2006-10-16 17:22 -------
Subject: Bug 29095

Author: bkoz
Date: Mon Oct 16 17:22:38 2006
New Revision: 117788

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117788
Log:
2006-10-16  Benjamin Kosnik  <bkoz@redhat.com>

        PR libstdc++/29095 continued
        * testsuite/lib/libstdc++.exp (v3_target_compile_as_c): Additions
        so that testing not in the build directory works for the "C"
        target language.


Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/testsuite/lib/libstdc++.exp


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29095