[FFmpeg-cvslog] r29011 - in trunk/libswscale: swscale.c swscale_internal.h swscale_template.c

[Gwenole Beauchesne]

On Mon, 23 Mar 2009, Reimar D?ffinger wrote:

> On Mon, Mar 23, 2009 at 09:33:40AM +0100, Gwenole Beauchesne wrote:
>> On Fri, 20 Mar 2009, Reimar D?ffinger wrote:
>>> I have no idea and not much interest and would not exclude a compiler
>>> bug, but it might well be a provision intended to allow combining 32 and
>>> 64 bit code, preserving the PIC pointer in rbx for use as ebx by any 32
>>> bit code.
>>
>> This is not possible. On some ancient x86_64 implementation, it was
>> (unofficially) possible to mix both but the engineers later on discouraged
>> this as the actual implementation was to be changed. I am talking of the
>> implementation (processor), the specs clearly forbids this.
>
> Forbid what? Certainly not switching between 64 bit and 32 bit code,
> then you couldn't run 32 bit programs at all anymore...

Mixing 64-bit and 32-bit execution code paths in the same binary 
(user-code). Executing 32-bit binary on x86_64 is no issue and doesn't 
require an explicit mode switch *in* the generated application.

e.g. opening an x86_32 DSO within an x86_64 binary and executing code from 
the library is not allowed, though technically possible on some 
processors.