Re: [Boost-users] [Lambda, Function, etc] Is static dangerous?

Subject: Re: [Boost-users] [Lambda, Function, etc] Is static dangerous?
From: Viatcheslav.Sysoltsev_at_[hidden]
Date: 2011-05-24 02:46:36

On Mon, 23 May 2011 15:40:06 +0200, Steven Watanabe <watanabesj_at_[hidden]>  
wrote:

>
> In C++03, local static anything is dangerous,
> because the initialization is not guaranteed
> to be thread safe.  It's safe in C++0x and
> both Boost.Function and Boost.Lambda are
> safe with parallel reads.
>

For Meyers singletons gcc generates thread-safe initialization code:

(gdb) list
1	struct A {
2	    A() {}
3	};
4	
5	int main()
6	{
7	    static A a;
8	    return 0;
9	}
(gdb) disas main
Dump of assembler code for function main():
    0x000000000040068c <+0>:	push   rbp
    0x000000000040068d <+1>:	mov    rbp,rsp
    0x0000000000400690 <+4>:	mov    eax,0x601040
    0x0000000000400695 <+9>:	movzx  eax,BYTE PTR [rax]
    0x0000000000400698 <+12>:	test   al,al
    0x000000000040069a <+14>:	jne    0x4006c3 <main()+55>
    0x000000000040069c <+16>:	mov    edi,0x601040
    0x00000000004006a1 <+21>:	call   0x400560 <__cxa_guard_acquire_at_plt>
    0x00000000004006a6 <+26>:	test   eax,eax
    0x00000000004006a8 <+28>:	setne  al
    0x00000000004006ab <+31>:	test   al,al
    0x00000000004006ad <+33>:	je     0x4006c3 <main()+55>
    0x00000000004006af <+35>:	mov    edi,0x601048
    0x00000000004006b4 <+40>:	call   0x4006ca <A::A()>
    0x00000000004006b9 <+45>:	mov    edi,0x601040
    0x00000000004006be <+50>:	call   0x400580 <__cxa_guard_release_at_plt>
    0x00000000004006c3 <+55>:	mov    eax,0x0
    0x00000000004006c8 <+60>:	leave
    0x00000000004006c9 <+61>:	ret
End of assembler dump.

>> void f( )
>> {
>>     namespace ll = boost::lambda;
>>     using boost::function;
>>
>>     typedef std::pair<int, int> int_pair;
>>
>>     static ll::placeholder1_type x;
>>     static function<int(const int_pair &)> second = ll::bind( &
>> int_pair::second, x );
>> }
>>
>

-- Slava