[arm-gnu] Static template member in assigned section -- section type conflict

[Carlos O'Donell]

On 1/22/2012 8:36 PM, Gene Smith wrote:
> //@!    test: g++ bad2.cpp
> //      bad2.cpp:18:25: error: priv causes a section type conflict
> 
> template<class t1, class t2>
> class outer
> {
> public:
>     t1        a;
>     static t2    b;
> };
> 
> template<class t1, class t2>
> t2 outer<t1, t2>::b
>         __attribute__((section(".s1")));
> 
> int main (void)
> {
>     static outer<int, int> priv __attribute__((section(".s1")));

You can't place common data and non-common data in the same section.

The conflict is as follows:

* The variable t2 in outer->t2 is static and therefore common data,
  there must only be one instance of t2 at all times.

* Moving t2 into .s1 causes section .s1 to be marked as common data,
  this is a flag that the linker must honour and it will bind other
  references to t2 to the common location in .s1 (that's how static
  is implemented in this case).

* In main you say you want to store the *entire* contents of the
  instantiated template into .s1, but .s1 is common data, and the
  object is not common data, and that is a conflict.
 
>     priv.a = 10;
>     priv.b = 10;
> }
> //@! end of file

The solution is to place priv into some *other* section.

You will never have *all* of priv in the same place because
the `static' clause makes that impossible for > 1 instances
of the object (given the current implementation for static).

Cheers,
Carlos.
-- 
Carlos O'Donell
Mentor Graphics / CodeSourcery
carlos at codesourcery.com
+1 (613) 963 1026