On Wed, Feb 26, 2025 at 07:44:37PM +0000, Pranav Kant via ffmpeg-devel wrote: > By default, all globals in C/C++ compiled by clang are allocated > in non-large data sections. See [1] for background on code models. > For PIC (Position independent code), this is fine as long as binary is > small but as binary size increases, users maybe want to use medium/large > code models (-mcmodel=medium) which moves data in to large sections. > As data in these large sections cannot be accessed using PIC code > anymore (as it may be too far away), compiler ends up using a different > instruction sequence when building C/C++ code -- using GOT to access > these globals (which can be relaxed by linker at link time if binary > ends up being smaller). However, assembly files continue to access these > globals defined in C/C++ files using older (and invalid instruction > sequence). So, we mark all such globals with an attribute that forces > them to be allocated in small sections allowing them to validly be > accessed from the assembly code. > > This patch should not have any affect on builds that use small code > model, which is the default mode. > > [1] https://eli.thegreenplace.net/2012/01/03/understanding-the-x64-code-models > > Signed-off-by: Pranav Kant <p...@google.com> > --- > libavcodec/ac3dsp.c | 2 ++ > libavcodec/cabac.c | 2 ++ > libavcodec/x86/constants.c | 8 ++++++++ > libavutil/attributes_internal.h | 15 +++++++++++++++ > 4 files changed, 27 insertions(+)
This produces many warnings:
CC libavcodec/svq1.o
In file included from libavcodec/svq1.h:40,
from libavcodec/svq1.c:35:
./libavutil/attributes_internal.h:43:5: warning: "ARCH_X86_64" is not defined,
evaluates to 0 [-Wundef]
43 | #if ARCH_X86_64 && defined(__ELF__) && __has_attribute(model)
| ^~~~~~~~~~~
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
If you fake or manipulate statistics in a paper in physics you will never
get a job again.
If you fake or manipulate statistics in a paper in medicin you will get
a job for life at the pharma industry.
signature.asc
Description: PGP signature
_______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
