[FFmpeg-devel] [PATCH 2/2] libavcodec: Set hidden visibility on global symbols accessed from x86_64 assembly

[Martin Storsjö]

On Wed, 27 Jul 2022, Thomas Guillem wrote:

> DECLARE_ALIGNED, DECLARE_ASM_ALIGNED, and DECLARE_ASM_CONST will include
> attribute_visibility_hidden.

Hmm, I'm not entirely sure that we should do that - if we should add such 
extra meaning to those macros.

How many symbols would it need to be applied on, if we don't apply it via 
these macros?

I was a bit concerned that DECLARE_ALIGNED could be used for e.g. stack 
local variables (where visibility doesn't make sense) - but we do have 
LOCAL_ALIGNED_* macros for that instead, so maybe it could work this way 
after all?

Do note, that these are currently defined in libavutil/mem.h, but after 
the next major bump they'll be in libavutil/mem_internal.h. Currently 
their contents are duplicated in the both, so any changes would need to 
apply to both.

I see that libavutil/mem.h (which is a public installed header) doesn't 
explicitly include libavutil/internal.h, so if someone uses those macros 
without including libavutil/internal.h, attribute_visibility_hidden would 
be undefined.

After the next bump, when these macros are entirely internal, this issue 
is much clearer (and at that point, I think it could be a bit more 
tolerable to extend their meaning to include visibility).

// Martin