Is there any method to preprocess enviroment variable before cargo run?

help
1

In my project, I want to set the environment variable for bindgen before run cargo.

such as this:

[env]
BINDGEN_EXTRA_CLANG_ARGS = "--sysroot=./asset/wasi-sysroot --target=wasm32-wasi -fvisibility=default"

But it's a relative path, the bindgen cannot use it.
I also try set environment variable in build.rs, but bindgen will run before build.rs.

2

toml does not have the function of parsing environment variables, if it can, i want use it:

SYS_ROOT={ value = "./asset/wasi-sysroot", relative = true }
BINDGEN_EXTRA_CLANG_ARGS = "--sysroot=${SYS_ROOT} --target=wasm32-wasi -fvisibility=default"
3

How do you run the bindgen? The recommended way is to call bindgen functions from the build.rs code.

4

I use the bindgen in my dependency ffmpeg-sys, so the bindgen will run before my build.rs.

5

Do you need the bindings from ffmpeg-sys's build script? Or only in the main ffmpeg-sys library? If the later you can use bindgen from ffmpeg-sys's build script. If the former, you did have to generate bindings twice when cross-compiling. Once for the host to run the build script and once for the target to build ffmpeg-sys itself.

6

This is my full project:

files:

 /tmp/ffmpeg-test $ tree . -a
.
├── .cargo
│   └── config.toml
├── Cargo.lock
├── Cargo.toml
└── src
    └── main.rs

3 directories, 4 files

env config:

 /tmp/ffmpeg-test $ cat .cargo/config.toml
[env]
BINDGEN_EXTRA_CLANG_ARGS = "--sysroot=./asset/wasi-sysroot --target=wasm32-wasi -fvisibility=default"

Cargo.toml:

/tmp/ffmpeg-test $ cat Cargo.toml
[package]
name = "ffmpeg-test"
version = "0.1.0"
edition = "2021"

[dependencies]
ffmpeg-sys-next="6"

main.rs:

 /tmp/ffmpeg-test $ cat src/main.rs
fn main() {
    println!("Hello, world!");
}

The bindgen will run in ffmpeg-sys-next's build.rs, I just want to set the environment BINDGEN_EXTRA_CLANG_ARGS before the bindgen run.

7

I see what you mean now.

8

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