[target.'cfg(all(target_arch="x86_64", not(debug_assertions)))'] in .cargo/config doesn't seem to work

[Boscop]

I have this in my .cargo/config:

[target.'cfg(all(target_arch="x86_64", not(debug_assertions)))'] 
rustflags = ["-Ctarget-feature=+crt-static", "-Ctarget-cpu=haswell"]

But when I do a release build and check the .exe with Dependency Walker, it STILL linked dynamically to vcruntime140.dll, so the cfg doesn't seem to work, why?

Here, someone is using both of these cfg variables in a .cargo/config file, too..

EDIT: It also doesn't work when I do cargo build --release --target=x86_64-pc-windows-msvc

[alexcrichton]

I believe this is a "bug" with the execution of rustc --print cfg unfortunately. When this is executed it's not passed opt-level flags, so it is always running with debug_assertions enabled (indicating that cfg is always enabled for resolution purposes)

[buybackoff]

-Zconfig-profile unstable feature and TiKV script https://github.com/tikv/tikv/blob/master/scripts/run-cargo.sh are relevant.

[Boscop]

@buybackoff So with -Zconfig-profile, can I specify rustflags per profile?

[Systemcluster]

What's the workaround for this? Configurations inside [target.'cfg(debug_assertions)'] or variations thereof seem to be completely ignored in case of rustc --print cfg, and the cfg(debug_assertions) section is always applied even during release builds. The documentation only states Do not try to match on debug_assertions or Cargo features like feature="foo". with no additional info.

There is also no option of specifying rustflags in a [profile.] section (which was requested in #7878).

The use-case here is simple but I assume very common: Using different target-cpu, target-feature and strip flags for relase and debug builds.