Re: [ppc64-linux]: register CONVERT_FROM_FUNC_PTR_ADDR method

Kevin Buettner
2003-06-11T22:42:56Z

On Jun 11, 3:53am, Jim Blandy wrote:

> 2003-06-11 Jim Blandy <jimb@redhat.com>
>
> * ppc-linux-tdep.c (ppc64_linux_convert_from_func_ptr_addr): New
> function.
> (ppc_linux_init_abi): Register it as the
> CONVERT_FROM_FUNC_PTR_ADDR method under the PPC64 Linux ABI.

Okay, but could you revise the comment to not mention RS/6000 and
to make it clear that the representation in question only pertains
to the 64-bit ABI?

> + /* Support for CONVERT_FROM_FUNC_PTR_ADDR(ADDR).
> +
> + Usually a function pointer's representation is simply the address
> + of the function. On the RS/6000 however, a function pointer is
> + represented by a pointer to a TOC entry. This TOC entry contains
> + three words, the first word is the address of the function, the
> + second word is the TOC pointer (r2), and the third word is the
> + static chain value. Throughout GDB it is currently assumed that a
> + function pointer contains the address of the function, which is not
> + easy to fix. In addition, the conversion of a function address to
> + a function pointer would require allocation of a TOC entry in the
> + inferior's memory space, with all its drawbacks. To be able to
> + call C++ virtual methods in the inferior (which are called via
> + function pointers), find_function_addr uses this function to get the
> + function address from a function pointer. */

Kevin