Add --config-override flag for configuration overrides

[trdthg]

This adds a --config-override option to the simulator to override parts of the base --config (or the built-in default). This is especially useful for first-party tests, some of which need the config to be slightly tweaked, for example Zclsd and Zcf are exclusive.

Fixes #806

[github-actions]

Test Results

2 328 tests  ±0   2 328 ✅ ±0   31m 8s ⏱️ -11s
    1 suites ±0       0 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 961ec5e. ± Comparison against base commit 5f5f02d.

♻️ This comment has been updated with latest results.

[pmundkur]

This seems useful! Some more documentation would be nice.

[Timmmm]

Looks pretty good to me. I'm still not sure what we do about error location reporting though.

[Timmmm]

I'm still not sure what we do about error location reporting though.

For the record, discussed in the meeting. We decided just to go with it. In theory you shouldn't ever get a parse error from Sail because we always parse with jsoncons first. That may not end up being 100% true if there are subtle differences between the parsers, or maybe things that Sail checks that the schema validation doesn't, but fingers crossed...

[trdthg]

I've made a clear distinction between parse and validate errors.

The code first run json::parse on every input config file, and then outputs the filename and location info for any caught errors.

$ ./build/c_emulator/sail_riscv_sim --config ./rv32d_v128_e32.json --config-override ./test_A.json test.elf
JSON parse error in override file ./test_A.json:
Extra comma at line 4 and column 4

Now it doesn't matter whether os << config_json uses pretty_print or not, because any formatting issues will have already cause an early return.

Finally, we perform the validation check. validate_config_schema now accepts a jsoncon::json, we can guarantee it will only throw schema-related exceptions.

$ ./build/c_emulator/sail_riscv_sim --config ./rv32d_v128_e32.json --config-override ./test_A.json test.elf
Error: Schema conformance check failed for merged configuration from ./rv32d_v128_e32.json, ./test_A.json:
- /base: Required property 'xlen' not found.

[Timmmm]

LGTM, nice work!

[jordancarlin]

This looks great! Probably worth mentioning this in the README and definitely warrants an entry in the Changelog. The PR title should also be updated because this is not exclusive to first-party tests.

[Timmmm]

We may want to add a proper man page style document for the simulator at this point, rather than just adding everything to the readme.

[pmundkur]

Nice! Minor tweaks to the Changelog and README.

[jordancarlin]

This looks great!