Re: Non-static variables and nested function pointers [bug #28392]

[Seth Goldberg]

Quoting Grégoire Sutre, who wrote the following on Thu, 24 Dec 2009:

> Seth Goldberg wrote:
>
> >   Your problem is probably lack of executable stack support, or at least 
> > you haven't linked your application with a linker mapfile that specifies an 
> > executable stack -- the callbacks require the use of trampolines to access 
> > local variables, which require an executable stack.
>
> Thanks a lot for your answer ! That explains it :-)
>
> I tried linking with -Wl,-z,execstack, but with no success, even though 
> readelf shows a new header with this option:
>
> Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
> GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RWE 0x4
>
> But the problem may come from NetBSD's default policy of non-executable stack 
> on i386 (http://www.netbsd.org/docs/kernel/non-exec.html).

 Exactly -- the presence of the execstack attribute in the segment is merely a 
request -- the kernel is free to discard it, and many OSes do, as you've found 
:).

 --S