[Bug c++/43330] New: trivial types are not being statically initialized

[Bug c++/43330] New: trivial types are not being statically initialized

[eric dot niebler at gmail dot com]

According to the C++0x status page
(http://gcc.gnu.org/gcc-4.5/cxx0x_status.html), "Standard Layout Types"
(http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2342.htm) have been
implemented in gcc-4.5. A quick test shows that trivial types are not being
statically initialized, as the paper requires. The following struct S is
trivial and the non-local constant s should be statically initialized, IIUC:

  struct S
  {
    S() {}
  };

  S const s{};

However, when compiled with -O2 -std=c++0x -S using the latest 4.5 snapshot, I
see the following assembly:

        .file   "main.cpp"
        .text
        .p2align 4,,15
        .def    __GLOBAL__I_main.cpp;   .scl    3;      .type   32;     .endef
__GLOBAL__I_main.cpp:
        pushl   %ebp
        movl    %esp, %ebp
        popl    %ebp
        ret
        .section        .ctors,"w"
        .align 4
        .long   __GLOBAL__I_main.cpp

Unless I'm mistaken, the global s is still being dynamically initialized.
Apologies in advance if I'm reading this wrong.


-- 
           Summary: trivial types are not being statically initialized
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: eric dot niebler at gmail dot com
 GCC build triplet: gcc-4.5-20100304


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43330

Re: [Bug c++/43330] New: trivial types are not being statically initialized

[Andrew Pinski]

Sent from my iPhone

On Mar 11, 2010, at 3:24 AM, "eric dot niebler at gmail dot com" <gcc-bugzilla@gcc.gnu.org 
 > wrote:

> According to the C++0x status page
> (http://gcc.gnu.org/gcc-4.5/cxx0x_status.html), "Standard Layout  
> Types"
> (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2342.htm)  
> have been
> implemented in gcc-4.5. A quick test shows that trivial types are  
> not being
> statically initialized, as the paper requires. The following struct  
> S is
> trivial and the non-local constant s should be statically  
> initialized, IIUC:
>
>  struct S
>  {
>    S() {}
>  };

The above is not a trivial type though. It has a non trivial default  
constructor. If you want a trivial constructor use either "= default"  
or delete it all together.


>
>  S const s{};
>
> However, when compiled with -O2 -std=c++0x -S using the latest 4.5  
> snapshot, I
> see the following assembly:
>
>        .file   "main.cpp"
>        .text
>        .p2align 4,,15
>        .def    __GLOBAL__I_main.cpp;   .scl    3;      .type    
> 32;     .endef
> __GLOBAL__I_main.cpp:
>        pushl   %ebp
>        movl    %esp, %ebp
>        popl    %ebp
>        ret
>        .section        .ctors,"w"
>        .align 4
>        .long   __GLOBAL__I_main.cpp
>
> Unless I'm mistaken, the global s is still being dynamically  
> initialized.
> Apologies in advance if I'm reading this wrong.
>
>
> -- 
>           Summary: trivial types are not being statically initialized
>           Product: gcc
>           Version: 4.5.0
>            Status: UNCONFIRMED
>          Severity: normal
>          Priority: P3
>         Component: c++
>        AssignedTo: unassigned at gcc dot gnu dot org
>        ReportedBy: eric dot niebler at gmail dot com
> GCC build triplet: gcc-4.5-20100304
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43330
>

[Bug c++/43330] trivial types are not being statically initialized

[pinskia at gmail dot com]

------- Comment #1 from pinskia at gmail dot com  2010-03-11 11:41 -------
Subject: Re:   New: trivial types are not being statically initialized



Sent from my iPhone

On Mar 11, 2010, at 3:24 AM, "eric dot niebler at gmail dot com"
<gcc-bugzilla@gcc.gnu.org 
 > wrote:

> According to the C++0x status page
> (http://gcc.gnu.org/gcc-4.5/cxx0x_status.html), "Standard Layout  
> Types"
> (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2342.htm)  
> have been
> implemented in gcc-4.5. A quick test shows that trivial types are  
> not being
> statically initialized, as the paper requires. The following struct  
> S is
> trivial and the non-local constant s should be statically  
> initialized, IIUC:
>
>  struct S
>  {
>    S() {}
>  };

The above is not a trivial type though. It has a non trivial default  
constructor. If you want a trivial constructor use either "= default"  
or delete it all together.


>
>  S const s{};
>
> However, when compiled with -O2 -std=c++0x -S using the latest 4.5  
> snapshot, I
> see the following assembly:
>
>        .file   "main.cpp"
>        .text
>        .p2align 4,,15
>        .def    __GLOBAL__I_main.cpp;   .scl    3;      .type    
> 32;     .endef
> __GLOBAL__I_main.cpp:
>        pushl   %ebp
>        movl    %esp, %ebp
>        popl    %ebp
>        ret
>        .section        .ctors,"w"
>        .align 4
>        .long   __GLOBAL__I_main.cpp
>
> Unless I'm mistaken, the global s is still being dynamically  
> initialized.
> Apologies in advance if I'm reading this wrong.
>
>
> -- 
>           Summary: trivial types are not being statically initialized
>           Product: gcc
>           Version: 4.5.0
>            Status: UNCONFIRMED
>          Severity: normal
>          Priority: P3
>         Component: c++
>        AssignedTo: unassigned at gcc dot gnu dot org
>        ReportedBy: eric dot niebler at gmail dot com
> GCC build triplet: gcc-4.5-20100304
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43330
>


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43330

[Bug c++/43330] trivial types are not being statically initialized

[eric dot niebler at gmail dot com]

------- Comment #2 from eric dot niebler at gmail dot com  2010-03-11 11:53 -------
You're right. Let me amend my example.

  struct S
  {
    S() = default;
    S(S const &) = default;
    S(int i) : i(i) {}
    int i;
  };

  S const s {1};

S would seem to satisfy the requirements for a trivial type now, correct? N2342
states:

"When an aggregate with static storage duration is initialized with a
brace-enclosed initializer-list, if all the member initializer expressions are
constant expressions, and the aggregate is a trivial type, the initialization
shall be done during the static phase of initialization"

GCC initializes s dynamically. That doesn't seem right. I see that constant
expressions are not yet implemented in gcc-4.5. Am I correct in assuming that
once constant expressions are implemented, this initialization will be static?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43330

[Bug c++/43330] trivial types are not being statically initialized

[eric dot niebler at gmail dot com]

------- Comment #3 from eric dot niebler at gmail dot com  2010-03-11 11:56 -------
Oops, it's not an aggregate. Disregard.


-- 

eric dot niebler at gmail dot com changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43330