Allow customizing CPU features about cargo-zigbuild HOT 3 CLOSED

currently for x86_64 targets we set -mcpu=pentium4.

This isn't true? We are only using pentium4 for i686 Linux target.

I think we should just go with solution 1: parse RUSTFLAGS to get target-cpu and target-features, then translate them to zig -mcpu flag.

from cargo-zigbuild.

currently for x86_64 targets we set -mcpu=pentium4.

This isn't true? We are only using pentium4 for i686 Linux target.

cargo-zigbuild/src/zig.rs

Lines 1017 to 1022 in 402ddac

	arch_str @ ("i586" | "i686") => {
	let cpu_arg = if arch_str == "i586" {
	"-mcpu=pentium"
	} else {
	"-mcpu=pentium4"
	};

I think we should just go with solution 1: parse RUSTFLAGS to get target-cpu and target-features, then translate them to zig -mcpu flag.

Good idea! In this way Rust land and C land uses the same CPU features, looks better.

from cargo-zigbuild.

After some investigation I'm now worrying about one case:

cargo-zigbuild zig cc as a compiler wrapper, now changes behavior when there are environmental changes (e.g. RUSTFLAGS). This actually conflicts with other compiler wrappers such as ccache, where they expect the compilers (and compiler wrappers) to produce exactly the same output using the same input files.

TL;DR, what will happen is that, for some crates that tries to invoke ccache internally (like rust-rocksdb), when user changes RUSTFLAGS, rebuild will not happen due to ccache not invalidated.

As an alternative, we could parse the RUSTFLAGS (from config files and env variables) when invoking cargo-zigbuild zigbuild, and then passing it explicitly as part of the compiler wrapper. This may be friendly with these compiler wrappers.

from cargo-zigbuild.