Re: Potential bug about the order of destructors of static objects and atexit() callbacks in C++?

[Markus Trippelsdorf <markus at trippelsdorf dot de>]

On 2016.08.01 at 18:16 +0800, lh mouse wrote:
> Hello GCC developers,
> 
> Reading the ISO C++ standard,
> > 3.6.4 Termination [basic.start.term]
> > 3 If the completion of the initialization of an object with
> > static storage duration is sequenced before a call to std::atexit
> > (see <cstdlib>, 18.5), the call to the function passed to std::atexit
> > is sequenced before the call to the destructor for the object. ...
> 
> Notwithstanding the vagueness of 'the completion of the initialization of an object',
> the following program:
> 
>     #include <cstdlib>
>     #include <cstdio>
>     
>     enum class state {
>         null,
>         initialized,
>         destroyed,
>     };
>     
>     extern void broken_atexit();
>     
>     struct global_data {
>         state s;
>     
>         global_data()
>             : s(state::null)
>         {
>             std::puts("delegated constructor");
>         }
>         global_data(int) 
>             : global_data()
>         {
>             s = state::initialized;
>             std::atexit(&broken_atexit);
>             std::puts("delegating constructor");
>         }
>         ~global_data(){
>             s = state::destroyed;
>         }
>     } data(1);
>     
>     void broken_atexit(){
>         if(data.s == state::destroyed){
>             std::puts("attempt to use a destroyed object?");
>             std::abort();
>         }
>         std::puts("okay");
>     }
>     
>     int main(){
>     }
> 
> , when compiled with GCC, results in use of a destroyed object:
> 
>     lh_mouse@lhmouse-dev:~$ g++ test.cc -std=c++11
>     lh_mouse@lhmouse-dev:~$ ./a.out 
>     delegated constructor
>     delegating constructor
>     attempt to use a destroyed object?
>     Aborted
>     lh_mouse@lhmouse-dev:~$
> 
> The reason of this problem is that GCC front-end registers the dtor after
> the delegating constructor returns, which is invoked before the other 
> callback registered inside the delegating constructor body.
> 
> The problem would be gone only if the GCC front-end registers the dtor after
> the delegated constructor returns.
> 
> Is this a GCC bug?

I don't think so. All compilers (clang, icc, visual C++) behave the
same. 
Also these kinds of questions regarding the C++ standard should be asked
on a more appropriate forum like stackoverflow.com or the ISO C++ group:
https://groups.google.com/a/isocpp.org/forum/?fromgroups#!forum/std-discussion


-- 
Markus