Andrew Brown (May 20 2020 at 23:02): Andrew Brown (May 20 2020 at 23:02):Does anyone by chance remember how to get an instance of cranelift_codegen::isa::x86::settings::Flags and not cranelift_codegen::settings::Flags? I want to use the ISA-specific one that's already configured by CLIF flags, e.g., without building a new instance of it.
bjorn3 (May 21 2020 at 12:44):It seems to be stored in cranelift_codegen::isa::x86::Isa.isa_flags:
https://docs.rs/cranelift-codegen/0.63.0/src/cranelift_codegen/isa/x86/mod.rs.html#33
Andrew Brown (May 21 2020 at 15:45):Good find; I guess I'll have to do some casting or something...
Andrew Brown (May 21 2020 at 17:41):I guess it's going to be unsafe but what is the "right" way to do this? I tried let x86_isa = &*(isa as *const isa::x86::Isa) but that doesn't work because isa is &dyn TargetIsa
Andrew Brown (May 21 2020 at 17:42):I get: casting &dyn isa::TargetIsa as *const isa::x86::Isa is invalid
Alex Crichton (May 21 2020 at 18:37):@Andrew Brown in general that's not a safe thing to do in Rust
Alex Crichton (May 21 2020 at 18:37):you can get away with it though by doing &*(ptr as *const dyn A as *const B)
Andrew Brown (May 21 2020 at 18:37)::+1: I figured
Alex Crichton (May 21 2020 at 18:37):the other "trick" is to add fn as_any(&self) -> &dyn Any; to the trait
Andrew Brown (May 21 2020 at 18:37):What is the better way?
Alex Crichton (May 21 2020 at 18:37):and then you'd call ptr.as_any().downcast_ref::<B>().unwrap()
Alex Crichton (May 21 2020 at 18:38):which would be a safe assertion of the type
Andrew Brown (May 21 2020 at 18:38):Yeah, I was looking into Any::downcast_ref... is this a preferable way to do things?
Alex Crichton (May 21 2020 at 18:39):yeah for dynamic type downcasting it's through Any
Andrew Brown (May 21 2020 at 18:39):Ok, I'll do that then; thanks!
Last updated: Nov 22 2024 at 16:03 UTC