Auto-Generate Tables in platform-support.md

[qb42]

This is a rough draft inspired by @ChrisDenton in #150501 (comment). I won't have much time to work on it until next month but I wanted to get it out there.

This is implemented as an mdbook preprocessor that pulls data from the rustc_target crate, so it will always be accurate.

Assuming this works as intended (I am not set up to test locally), it's still missing the following:

• Links to target detail pages
• Footnotes

[Noratrieb]

This is very cool! I started a similar effort a while ago in #120745 but never got to completing it. Maybe some of the code in the linked PR thee may be useful

[qb42]

@Noratrieb Thanks, I'll take a look.

[qb42]

Alright, I'm set up properly now so no more failing tidy or pushing obvious mistakes.

Unfortunately it looks like depending on rustc_target directly is a dead-end, I'm getting a variety of errors related to it being a compiler-internal crate that is supposed to be compiled as part of bootstrap. The commit I just pushed (8c1125f) is my last attempt in that direction unless someone else has a solution.

I'm going to switch to pulling data from rustc -Z unstable-options --print all-target-specs-json and see how that goes.

[Noratrieb]

Executing rustc like that seems like the best approach, yes.

[rust-log-analyzer]

The job aarch64-gnu-llvm-20-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

##[endgroup]
[TIMING:start] doc::RustcBook> { target: aarch64-unknown-linux-gnu, name: "rustc", src: "/checkout/obj/build/aarch64-unknown-linux-gnu/md-doc/rustc", parent: Some(RustcBook { build_compiler: Compiler { stage: 1, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target: aarch64-unknown-linux-gnu, validate: false }), languages: [], build_compiler: None }
Rustbook (aarch64-unknown-linux-gnu) - rustc
 INFO Book building has started
ERROR The command `cargo run --manifest-path ../../../../src/tools/mdbook-rustc/Cargo.toml` wasn't found, is the `rustc-gen-target-tables` preprocessor installed? If you want to ignore this error when the `rustc-gen-target-tables` preprocessor is not installed, set `optional = true` in the `[preprocessor.rustc-gen-target-tables]` section of the book.toml configuration file.
Error: Unable to run the preprocessor `rustc-gen-target-tables`
 Caused By: No such file or directory (os error 2)
Bootstrap failed while executing `--stage 2 test --skip tests --skip coverage-map --skip coverage-run --skip library --skip tidyselftest`
Command `/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools-bin/rustbook build /checkout/obj/build/aarch64-unknown-linux-gnu/md-doc/rustc -d /checkout/obj/build/aarch64-unknown-linux-gnu/doc/rustc --rust-root /checkout` failed with exit code 101
Created at: src/bootstrap/src/core/build_steps/tool.rs:1612:23
Executed at: src/bootstrap/src/core/build_steps/doc.rs:176:18

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:36:30
  local time: Mon Jan  5 19:30:07 UTC 2026
  network time: Mon, 05 Jan 2026 19:30:07 GMT
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"

[rust-bors]

☔ The latest upstream changes (presumably #151409) made this pull request unmergeable. Please resolve the merge conflicts.

[Dylan-DPC]

@qb42 any updates on this? thanks

[qb42]

@Dylan-DPC IIRC, the last commit I pushed worked on my machine (though without links or footnotes). I put this to the side after failing to figure out what the issue with the filepath was and forgot about it. I'll revisit in the next couple of days and see if I can get it working now I'm not in school.