Profile based `rustflags` generate unknown unstable option: `build-std`

[Wyvern]

When using some -Z flags in profile based rustflags such as build-std build-std-features panic-in-drop=abort, the compiler generate error unknown unstable option: build-std ....

for example: a customized src profile with rustflags:

[profile.src]
inherits = "release"
panic="abort"
rustflags = ["-Zbuild-std=core,alloc,std,"-Zbuild-std-features=panic_immediate_abort","-Zpanic-in-drop=abort"]
[profile.std.build-override]
inherits = "release"
[profile.std.package."*"]
inherits = "release"

When build using cargo b --profile src the above error raised.

Is it a bug of cargo-features = ["profile-rustflags"] or something else?

[ehuss]

Transferred to rust-lang/cargo

rustflags in a profile are flags that apply to rustc. -Zbuild-std is a flag for cargo. Cargo's flags cannot be set from a profile. I recommend using an alias to set which flags to use.

[Wyvern]

Thx @ehuss , that make sense.

Use -Zpanic-in-drop=abort in [profile.src] rustflags combined with set alias src= "build --profile src -Zbuild-std=std... --target <target>" compiler hit error: the crate std is compiled with the panic-in-drop strategy unwind which is incompatible with this crate's strategy of abort.

But, if set -Zpanic-in-drop=abort in [build] rustflags everything works fine. It seems that profile based rustflags wasn't aware of cargo -Zbuild-std flags in this scenario.

[ehuss]

Indeed that flag does not work in a profile rustflags because profile rustflags are being passed to build scripts. That is one of the concerns registered with the design over on the tracking issue at #10271.

[ehuss]

I'm going to close, as I don't think cargo will be parsing profile.rustflags to validate the flags. As for the build-script issue, that is an open question on the design tracked in #10271.