SFRAME version 3 support

[mati865]

Linking anything on up to date Arch Linux now fails with:

wild: error: Failed to parse SFrame header at offset 0: Unsupported SFrame version 3 (expected 2)

Apparently Binutils 2.46 now defaults to SFRAME version 3.

[lapla-cogito]

It might have been better to skip rather than bail when trying to process an unsupported SFrame version. Sorry for that.

However, since the specification isn't documented at https://sourceware.org/binutils/wiki/sframe, I'm unsure how reliably we can implement SFrame V3 at this stage.

[mati865]

Yeah, that's exactly what I'm planning to do for the short term.

Documentation is sort of all around the place. For the version 3 you can find the docs here: https://sourceware.org/binutils/docs-2.46/sframe-spec.html
Version 2 docs are best read at https://sourceware.org/binutils/docs-2.45/sframe-spec.html

[lapla-cogito]

Ah, I didn't know that link. Thanks!

[mati865]

This SFrame sh*t show is not funny. Apparently, Arch Linux had to disable SFrame support in glibc to ease version 2 to version 3 transition and reenabled it only recently. Except it doesn't work for me with backtrace() called in C. I had even rebuilt glibc and rebooted.

In test case from run_sframe_backtrace_test, backtrace() returns 1 with .eh_frame* removed and 6 without removing them.

There are a few bugs in our current version 2 implementation that I wanted to fix before working on version 3, but I cannot test anything at the moment. I'll try

To make things more complicated, as supports only the latest version of SFrame:

❯ as --help | rg sframe-
  --gsframe-<N>           generate SFrame version <N> information. 3 == <N>

So, --gsframe-2 is declined while --gsframe-3 works with Binutils 2.46. This makes me wonder whether supporting multiple SFrame versions is even feasible.