segfault with std::allocator

segfault with std::allocator

[Toon Knapen]

Following problem segfaults with gcc 3.2.2 inside the deallocate 
function. AFAICT however, allocation and deallocation of 0 number of 
objects are allowed ?

<code>
<code>
#include <memory>

int main()
{
    std::allocator< int > int_alloc ;
    int* p = int_alloc.allocate( 0 ) ;
    int_alloc.deallocate( p, 0 ) ;
    return 0 ;
}
</code>

Re: segfault with std::allocator

[Eljay Love-Jensen]

Hi Toon,

The deallocate function MUST NOT by passed in a NULL pointer.  (According 
to ISO 14882.)

You can fix your code by...

#include <memory>
int main()
{
    std::allocator< int > int_alloc ;
    int* p = int_alloc.allocate( 0 ) ;
    if(p) int_alloc.deallocate( p, 0 ) ;
    return 0 ;
}

HTH,
--Eljay

Re: segfault with std::allocator

[Toon Knapen]

Eljay Love-Jensen wrote:

> 
> Hi Toon,
> 
> The deallocate function MUST NOT by passed in a NULL pointer.  
> (According to ISO 14882.)
> 


But 20.4.1.1 par 8 only says "p shall be a pointer obtained from 
allocate(). n shall equal the value passed as the first argument to the 
invocation of allocate which returned p". Next as a not is added that it 
uses '::operator delete' and delete is allowed to be called on a NULL 
pointer.

Re: segfault with std::allocator

[Eljay Love-Jensen]

Hi Toon,

You're not calling delete, your calling int_alloc.deallocate(p, 0);

And the deallocate routine (in ISO 14882, table 32 in 20.1.5) specifically 
says "p must not be null".

--Eljay