The ability to generate a C library was lost in recent versions

[julienfreche]

In the past, we worked on the ability to generate a C library with Sail rather than a C executable. That was useful to use the generated code in the context of a full emulator or a VMM.

However, it looks like refactorings in the C backend eliminated that option. Was that on purpose and/or is there still a desire from the maintainers to keep this as a working option in the future?

For example, those changes were lost:
#81
#83
#164

[arichardson]

I have used sail generated code as a library somewhat recently. For exxample: https://github.com/CTSRD-CHERI/cheri-compressed-cap/blob/master/test/contrib/sail_compression_128.c contains sail generated code that I used to compare against a C implementation of the same logic.
To generate it I used https://github.com/CTSRD-CHERI/cheri-compressed-cap/blob/master/test/regen_sail_c_code.sh: The flags -c -c_no_main -c_prefix sailgen_ -c_specialize seemed sufficient to get it working. That said those files are linked into a test binary rather than built as a standalone .so so it's possible there are some things that are broken.

[julienfreche]

Thank you for the quick reply and for giving this example. That's a start, but, it does not seem to cover a few features that are very useful to a VMM use case like:

• Ability to override the read and write to the CPU registers as seen by Sail (useful to remap them to the actual registers and/or a shared state stored somewhere)
• Ability to manually provide some function outside of sail (read or write to RAM for example)

or am I mistaken?

[Alasdair]

Maintaining two separate copies of the Sail C backend was too much work with the code duplication involved. I naively thought at the time that I could transition uses of the older C backend to the new one and fix the code duplication by removing the older backend, but that just wasn't realistic. When I switched the build system to dune (about 2 years ago roughly) and moved each Sail backend into a separate plugin, I wasn't sure if anyone was actively using the c2 output and it didn't fit neatly into the more cleanly separated architecture, so I decided to drop it - thinking that if anyone was they would probably notice and raise an issue. I see that finally happened!

My plan after that was to add these features back in by parameterising the original backend, preserving backwards-compatibility, but I just never had either the time or a pressing use-case to actually implement that.

[julienfreche]

There is definitely an interest from our side as we still use sail to perform emulation in certain cases. I just only recently looked into upgrading our ARM model to a newer version hence the belated feedback. Thanks for the explanation.

[trdthg]

We also have people here who are interested in Sail generating C libraries(with header file used for ffi calls)
maybe related to #215