Enable Control Flow Guard in rustbuild

[ajpaverd]

Now that Rust supports Control Flow Guard (#68180), add a config.toml option to build the standard library with CFG enabled.

r? @nagisa

[nagisa]

@bors r+ option disabled by default, no danger in adding it.

[bors]

📌 Commit ede8019409194d2ce02f2e5188c706f90f504e70 has been approved by nagisa

[ajpaverd]

Thanks for the super fast review @nagisa!

[nagisa]

@bors r- on commentary above.

r? @Mark-Simulacrum

[nikic]

Isn't this something that should be happening through -Z build-std, similar to how it is (since recently) done for sanitizer builds?

[ajpaverd]

Isn't this something that should be happening through -Z build-std, similar to how it is (since recently) done for sanitizer builds?

Thanks for the suggestion @nikic - I hadn't seen -Z build-std. Did I understand correctly that this approach would not require changes to rustbuild (i.e. libstd would be rebuilt with Control Flow Guard enabled when the -Z control_flow_guard flag was set for rustc)?

On the other hand, is there some way to avoid rebuilding libstd every time and always use the same version (with Control Flow Guard enabled)?

[rust-highfive]

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2020-02-10T14:49:03.6652346Z ========================== Starting Command Output ===========================
2020-02-10T14:49:03.6669792Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/135719e1-3aa1-4232-8b1b-2e2177705451.sh
2020-02-10T14:49:03.6869039Z 
2020-02-10T14:49:03.6928806Z ##[section]Finishing: Disable git automatic line ending conversion
2020-02-10T14:49:03.6934348Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/68824/merge to s
2020-02-10T14:49:03.6936203Z Task         : Get sources
2020-02-10T14:49:03.6936233Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-02-10T14:49:03.6936280Z Version      : 1.0.0
2020-02-10T14:49:03.6936310Z Author       : Microsoft
---
2020-02-10T14:49:04.5516567Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-02-10T14:49:04.5604040Z ##[command]git config gc.auto 0
2020-02-10T14:49:04.5683988Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-02-10T14:49:04.5781797Z ##[command]git config --get-all http.proxy
2020-02-10T14:49:04.5922275Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/68824/merge:refs/remotes/pull/68824/merge

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[Mark-Simulacrum]

r=me with comment resolved

[Mark-Simulacrum]

Please also squash the commits, forgot to mention that in my previous comment.

[Mark-Simulacrum]

@bors r+

[ajpaverd]

Thanks @Mark-Simulacrum! Is bors still waiting for me to do something here?

[nikic]

@bors r=Mark-Simulacrum

Looks like bors just missed this.

[bors]

📌 Commit 87df124 has been approved by Mark-Simulacrum