[Bug c++/40192] New: Unable to use std::vector with typedef'd array types

[Bug c++/40192] New: Unable to use std::vector with typedef'd array types

[coleb at eyesopen dot com]

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The following code will not compile in gcc 4.3.2 on Ubuntu 8.10

#include <vector>

typedef float float4[4];

int main()
{
  std::vector<float4> vals;
}

I get the following compilation error:
/usr/include/c++/4.3/bits/stl_construct.h: In function ‘void
std::_Destroy(_Tp*) [with _Tp = float [4]]’:
/usr/include/c++/4.3/bits/stl_construct.h:103:   instantiated from ‘void
std::_Destroy(_ForwardIterator, _ForwardIterator) [with _ForwardIterator =
float (*)[4]]’
/usr/include/c++/4.3/bits/stl_construct.h:128:   instantiated from ‘void
std::_Destroy(_ForwardIterator, _ForwardIterator, std::allocator<_T2>&) [with
_ForwardIterator = float (*)[4], _Tp = float [4]]’
/usr/include/c++/4.3/bits/stl_vector.h:300:   instantiated from
‘std::vector<_Tp, _Alloc>::~vector() [with _Tp = float [4], _Alloc =
std::allocator<float [4]>]’
test_float4.cpp:7:   instantiated from here
/usr/include/c++/4.3/bits/stl_construct.h:88: error: request for member ‘~float
[4]’ in ‘* __pointer’, which is of non-class type ‘float [4]’

The code does compile in gcc 3.4 and gcc 4.1.


-- 
           Summary: Unable to use std::vector with typedef'd array types
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: coleb at eyesopen dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo dot carlini at oracle dot com]

------- Comment #1 from paolo dot carlini at oracle dot com  2009-05-18 22:34 -------
I'll fix it momentarily.


-- 

paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |paolo dot carlini at oracle
                   |dot org                     |dot com
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-05-18 22:34:29
               date|                            |
            Summary|Unable to use std::vector   |[4.4/4.5 Regression] Unable
                   |with typedef'd array types  |to use std::vector with
                   |                            |typedef'd array types
   Target Milestone|---                         |4.4.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo at gcc dot gnu dot org]

------- Comment #2 from paolo at gcc dot gnu dot org  2009-05-18 23:16 -------
Subject: Bug 40192

Author: paolo
Date: Mon May 18 23:16:20 2009
New Revision: 147680

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=147680
Log:
2009-05-18  Paolo Carlini  <paolo.carlini@oracle.com>

        PR libstdc++/40192
        * include/bits/stl_construct.h (struct _Destroy_aux): Add.
        (_Destroy(_ForwardIterator, _ForwardIterator)): Use the latter.
        * testsuite/23_containers/vector/40192.cc: New.


Added:
    trunk/libstdc++-v3/testsuite/23_containers/vector/40192.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/bits/stl_construct.h


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo at gcc dot gnu dot org]

------- Comment #3 from paolo at gcc dot gnu dot org  2009-05-18 23:17 -------
Subject: Bug 40192

Author: paolo
Date: Mon May 18 23:16:48 2009
New Revision: 147681

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=147681
Log:
2009-05-18  Paolo Carlini  <paolo.carlini@oracle.com>

        PR libstdc++/40192
        * include/bits/stl_construct.h (struct _Destroy_aux): Add.
        (_Destroy(_ForwardIterator, _ForwardIterator)): Use the latter.
        * testsuite/23_containers/vector/40192.cc: New.


Added:
   
branches/gcc-4_4-branch/libstdc++-v3/testsuite/23_containers/vector/40192.cc
Modified:
    branches/gcc-4_4-branch/libstdc++-v3/ChangeLog
    branches/gcc-4_4-branch/libstdc++-v3/include/bits/stl_construct.h


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo dot carlini at oracle dot com]

------- Comment #4 from paolo dot carlini at oracle dot com  2009-05-18 23:18 -------
Fixed for 4.4.1.


-- 

paolo dot carlini at oracle dot com changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[jeff at schwabcenter dot com]

------- Comment #5 from jeff at schwabcenter dot com  2009-05-19 16:36 -------
Whoa whoa whoa...  The behavior seemed correct before.  vector<float[4]>
shouldn't even be legal.  Shouldn't the compiler to catch such a mistake?


-- 

jeff at schwabcenter dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jeff at schwabcenter dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo dot carlini at oracle dot com]

------- Comment #6 from paolo dot carlini at oracle dot com  2009-05-19 16:42 -------
I think that, in any case, we cannot do anything wrong here: we are simply
restoring an implementation detail of the previous implementations, which, as a
side effect, allows to compile this specific kind of snippet. Indeed, other
implementations also swallow it. So, let's take the legal issues aside, and
move on. If you figure specific details telling it's illegal just add it, as a
note, but certainly diagnostic is not required.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[jeff at schwabcenter dot com]

------- Comment #7 from jeff at schwabcenter dot com  2009-05-19 17:09 -------
I understand the desire for backward compatibility, but are the semantics
actually the same?  Are the vector values arrays, or do they decay to pointers?
 Section 23.1 says standard container elements have to be CopyConstructible and
assignable, but raw arrays are neither.

Is there at least some flag to re-enable the diagnostic?  If you're saying this
is a necessary evil for reasons of backward compatibility, then I understand,
but in my opinion, this is a step backward that will confuse newcomers like
Brian and hurt cross-compatibility.  Speaking strictly as a GCC user, I don't
see any reason to reduce the compiler's ability to deduce an obvious mistake
with ill-defined semantics.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo dot carlini at oracle dot com]

------- Comment #8 from paolo dot carlini at oracle dot com  2009-05-19 17:12 -------
This is not going to change again. We had this behaviour forever until 4.3.x
and all the major implementations outside GCC behave the same as GCC now (and
before the change of behavior).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[jeff at schwabcenter dot com]

------- Comment #9 from jeff at schwabcenter dot com  2009-05-19 17:32 -------
OK.  Thanks for the explanation.  Are the semantics documented somewhere?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo dot carlini at oracle dot com]

------- Comment #10 from paolo dot carlini at oracle dot com  2009-05-19 17:38 -------
Look closely at the patch I committed, I changed *nothing* of the actual
behavior of the containers. Thus the semantics is exactly the same as before,
only, the destructor in not called explicitly anymore on such element type,
because the destructor is trivial.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[coleb at eyesopen dot com]

------- Comment #11 from coleb at eyesopen dot com  2009-05-19 17:57 -------
(In reply to comment #10)
> Look closely at the patch I committed, I changed *nothing* of the actual
> behavior of the containers. Thus the semantics is exactly the same as before,
> only, the destructor in not called explicitly anymore on such element type,
> because the destructor is trivial.
> 

Yup, even though you can declare a vector<float4>, you can't do anything useful
with it. 

typedef float cl_float4[4] __attribute__((aligned(16)));

#include <vector>

int main()
{
  std::vector<cl_float4> vals(1);
  cl_float4 a = {1.0f, 2.0f, 3.0f, 4.0f};
  vals.push_back(a);
}

/usr/local/lib/gcc/x86_64-unknown-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/stl_algobase.h:412:
error: ISO C++ forbids assignment of arrays

Does seem strange to allow vector<float4> to be compilable, but eh, lesson
learned, stay away from array types in C++. 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[jeff at schwabcenter dot com]

------- Comment #12 from jeff at schwabcenter dot com  2009-05-19 18:07 -------
What he said.  I'm perusing your patch, and I appreciate that you removed an
artificial restriction.  The right place to catch this is up front, in a
concept check, rather than in _Destroy; since I'm not about to add the check
myself, I'm hardly in a position to criticize.  The diagnostic did have the
nice property of catching a real, semantic error, though, and it seems a shame
to let a known error go unreported.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192

[Bug c++/40192] [4.4/4.5 Regression] Unable to use std::vector with typedef'd array types

[paolo dot carlini at oracle dot com]

------- Comment #13 from paolo dot carlini at oracle dot com  2009-05-19 18:19 -------
It's life, you know ;)


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40192