ld: warning: could not create compact unwind

[Daniel Schürmann]

When trying to link ffmpeg statically with Mixxx on macOS, the Apple linker is complaining:

2021-08-18T22:06:41.3473950Z ld: warning: could not create compact unwind for _ff_cfhd_init_vlcs: stack subq instruction is too different from dwarf stack size
2021-08-18T22:06:41.3475230Z ld: warning: could not create compact unwind for _ff_rl_init_vlc: stack subq instruction is too different from dwarf stack size

This happens with gcc and clang 12.0.0.12000032

The issue was original reported here:
​https://github.com/microsoft/vcpkg/issues/19699

Only these two functions are reported. When I disable cfhd encoder and decoder, one warning disappears.

I can also specify LDFLAGS="-Wl,-no_compact_unwind" to make remove this warning, but that will affect all functions.

Both functions locate big arrays on the stack, my guess it that these arrays are too big for compact unwind.

What is the best option to lower the used stack?

Do you know what is the limit for unwinding, the dwarf stack size?

Thank you.

[Carl Eugen Hoyos]

While this has little similarities with a valid ticket, I believe ff_cfhd_init_vlcs() and ff_rl_init_vlc() might have issues on some mobile platforms.

[Balling]

This can fix it ​https://patchwork.ffmpeg.org/project/ffmpeg/patch/AS8P250MB0744D466DE062DB6D899FB478F7D9@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM/

[Carl Eugen Hoyos]

Replying to Balling:

This can fix it ​https://patchwork.ffmpeg.org/project/ffmpeg/patch/AS8P250MB0744D466DE062DB6D899FB478F7D9@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM/

No.

[Balling]

Is your patch better?

[Elon Musk]

Carl patch is too trivial, and not gonna be applied.

[Balling]

So does this fix it on MacOS? e6d89d0efd9194198d9964e47bf428be222594ea

I will ping on github...