如何根据 Cargo 功能选择性地传递 rustc 标志? [英] How can I optionally pass rustc flags depending on a Cargo feature?

问题描述

当将 -C target-cpu=native 标志传递给 rustc 时，我正在编写的程序运行得更快.我想给用户一个简单的、与平台无关的方式来在编译时启用它，所以我在 Cargo.toml 中添加了一个 Cargo 特性 cpu_native = [] 并在我的项目中创建了这个 Cargo 配置:

[target.'cfg(cpu_native)']rustflags = ["-C", "target-cpu=native"]

然而，这对我的程序没有影响，并且将 --features cpu_native 传递给 Cargo 甚至不会触发重新编译.更改为以下 Cargo 配置确实会强制使用更快的指令重新编译:

[构建]rustflags = ["-C", "target-cpu=native"]

但是，这将使用具有默认 Cargo 功能的 target-cpu=native 进行编译，这不是我想要的.从 Cargo 书中，我想要的似乎是可能的，但我看不出我做错了什么.

解决方案

我认为不支持(还?).我增强了 Cargo 以打印出解析时检查的配置标志:

[名称(调试断言")，名称(proc_macro")，KeyPair("target_arch", "x86_64"),KeyPair("target_endian", "little"),KeyPair("target_env", ""),KeyPair("target_family", "unix"),KeyPair("target_os", "macos"),KeyPair("target_pointer_width", "64"),名称(unix")，]

<块引用>

[target.'cfg(cpu_native)']

这是 Cargo 功能的错误语法；它通常是 cfg(feature = "cpu_native").

The program I'm writing runs much faster when the -C target-cpu=native flag is passed to rustc. I want to give users a simple, platform-independent way to enable this when compiling, so I added a Cargo feature cpu_native = [] in Cargo.toml and created this Cargo config in my project:

[target.'cfg(cpu_native)']
rustflags = ["-C", "target-cpu=native"]

However, this has no effect on my program, and passing --features cpu_native to Cargo does not even trigger a recompile. Changing to the following Cargo config does force re-compilation with faster instructions:

[build]
rustflags = ["-C", "target-cpu=native"]

However, this will compile with target-cpu=native with the default Cargo features, which was not what I wanted. From the Cargo book, what I want seems to be possible, but I don't see what I'm doing wrong.

解决方案

I don't think this is supported (yet?). I enhanced Cargo to print out what config flags are checked against when resolving:

[
    Name("debug_assertions"),
    Name("proc_macro"),
    KeyPair("target_arch", "x86_64"),
    KeyPair("target_endian", "little"),
    KeyPair("target_env", ""),
    KeyPair("target_family", "unix"),
    KeyPair("target_os", "macos"),
    KeyPair("target_pointer_width", "64"),
    Name("unix"),
]

[target.'cfg(cpu_native)']

This is the incorrect syntax for a Cargo feature; it would normally be cfg(feature = "cpu_native").

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