[ffmpeg] build without PIC

[talregev]

Operating system

wsl2 ubuntu 22.04

Compiler

gcc

Steps to reproduce the behavior

./vcpkg install ffmpeg
readelf --relocs installed/x64-linux/lib/libavcodec.a  | awk '{print $3}' | sort -u | grep R_X86_64

tested on ffmpeg 5.1.2.

Failure logs

When I run the command:

R_X86_64_32
R_X86_64_64
R_X86_64_GOTPCREL
R_X86_64_PC32
R_X86_64_PLT32
R_X86_64_REX_GOTP

It has the line R_X86_64_32 that tell it compile without PIC even with the flag --enable-pic that already set on the port.

Additional context

When I compile with shared the output of the command:

R_X86_64_64
R_X86_64_GLOB_DAT
R_X86_64_JUMP_SLO
R_X86_64_RELATIVE

Tested on ffmpeg 5.1.2.
Not sure how to fix it.
Not sure if the same happen on the ffmpeg 6.0.

[Cheney-W]

This issue could be reproduced with the latest vcpkg 2023-04-07-bedcba5172f5e4b91caac660ab7afe92c27a9895.

vxincwa@vxincwa-linux:~/cheney$ readelf --relocs installed/x64-linux/lib/libavcodec.a  | awk '{print $3}' | sort -u | grep R_X86_64
R_X86_64_32
R_X86_64_64
R_X86_64_GOTPCREL
R_X86_64_PC32
R_X86_64_PLT32
R_X86_64_REX_GOTP

[talregev]

It still relevant.

[dg0yt]

Given the recent OpenSSL experience, I would suspect some (upstream) assembler code to not be relocatable. PIC compiler flags change asm generation from upstream C code, but they won't affect what is already written in assembler. You can build with PIC flags but still get binaries which are nor relocatable.

[dg0yt]

Hitting rtabmap, #37651.

[Vinayak-YB]

Hey people, I'm still facing the relocation issue with ffmpeg (specifically libavcodec) . Any solution ?

[dg0yt]

Not a port bug, although reported repeatedly.

Other than the the message suggests, the compiler is run with -fPIC.
But this doesn't affect the code which isn't compiled (to assembler) but written in assember.

The error occurs due to wrong usage:
When using the static ffmpeg binaries in shared libs, it is expected to use -Bsymbolic linker flags (or -Wl,-Bsymbolic).

Cf. #17292 (comment), #19273 (comment).

[Vinayak-YB]

Hi @dg0yt Thanks a lot. This helped resolve my error

[talregev]

@dg0yt Where do you put the -Bsymbolic?
On ffmpeg or on the lib that consume it?

[dg0yt]

On the consumer.