warning: Compiler family detection failed on MacOS

[LinusChen-yf]

When cross-compiling for Windows MSVC on macOS, I encounter a warning. My local machine has clang-cl installed, and the compiled output appears to be normal. The warning is as follows:

warning: VibeService@0.1.0: Compiler family detection failed due to error: ToolExecError: command did not execute successfully (status code exit status: 1): "clang-cl" "-E" "/Users/linuschen/rust_projects/my_project/target/x86_64-pc-windows-msvc/release/build/MyProject-0a0478fd59c1ac07/out/11385383916581809335detect_compiler_family.c"

I found that there was an issue before, but I still encountered this problem in the latest version 1.2.17
#1327

I found the problem by debugging the source code. After the first run_output judgment failed, an error was directly returned, and there was no chance to judge stdout.contains("-Wslash-u-filename"), which caused a warning to be thrown.

cc-rs/src/tool.rs

Lines 201 to 216 in 59578ad

	let stdout = run_output(
	Command::new(path).arg("-E").arg(tmp.path()),
	&compiler_detect_output,
	)?;
	let stdout = String::from_utf8_lossy(&stdout);
	if stdout.contains("-Wslash-u-filename") {
	let stdout = run_output(
	Command::new(path).arg("-E").arg("--").arg(tmp.path()),
	&compiler_detect_output,
	)?;
	let stdout = String::from_utf8_lossy(&stdout);
	guess_family_from_stdout(&stdout, path, args, cargo_output)
	} else {
	guess_family_from_stdout(&stdout, path, args, cargo_output)
	}

I want to modify run_output so that there is output when it fails to determine whether it is a real failure. However, if the child fails to execute and I try to print stdout, it is empty, so I don't know if there is a better way to modify it.

cc-rs/src/command_helpers.rs

Lines 347 to 365 in 59578ad

	pub(crate) fn run_output(cmd: &mut Command, cargo_output: &CargoOutput) -> Result<Vec<u8>, Error> {
	// We specifically need the output to be captured, so override default
	let mut captured_cargo_output = cargo_output.clone();
	captured_cargo_output.output = OutputKind::Capture;
	let mut child = spawn(cmd, &captured_cargo_output)?;
	let mut stdout = vec![];
	child
	.stdout
	.take()
	.unwrap()
	.read_to_end(&mut stdout)
	.unwrap();
	// Don't care about this output, use the normal settings
	wait_on_child(cmd, &mut child, cargo_output)?;
	Ok(stdout)
	}

[NobodyXu]

I think the better way would be to prevent clang-cl from failing, is there any line in the logging that shows the error for clang-cl?

[LinusChen-yf]

Indeed, what you said makes sense. I tested the command clang-cl -E -- /my-path/cc-rs/src/detect_compiler_family.c on Windows, Linux, and MacOS. It can run normally without errors, and eliminates warnings on MacOS.
I submitted a PR, please help me review it, thank you!