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Don't emit rerun-if-changed on llvm-config if using system LLVM

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The code was broken because it printed "llvm-config" instead of the
absolute path to the llvm-config executable, causing Cargo to always
rebuild librustc_llvm if using system LLVM.

Also, it's not the build system's job to rebuild when a system library
changes, so we simply don't emit "rerun-if-changed" if a path to LLVM
was not explicitly provided.
This commit is contained in:
Luca Barbieri 2020-04-10 22:42:19 +02:00 committed by Mark Rousskov
parent 53d58dbf5f
commit 3dd500de37
1 changed files with 20 additions and 10 deletions
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30
src/librustc_llvm/build.rs
View File

@ -24,18 +24,28 @@ fn main() {
build_helper::restore_library_path();
let target = env::var("TARGET").expect("TARGET was not set");
let llvm_config = env::var_os("LLVM_CONFIG").map(PathBuf::from).unwrap_or_else(|| {
if let Some(dir) = env::var_os("CARGO_TARGET_DIR").map(PathBuf::from) {
let to_test =
dir.parent().unwrap().parent().unwrap().join(&target).join("llvm/bin/llvm-config");
if Command::new(&to_test).output().is_ok() {
return to_test;
let llvm_config =
env::var_os("LLVM_CONFIG").map(|x| Some(PathBuf::from(x))).unwrap_or_else(|| {
if let Some(dir) = env::var_os("CARGO_TARGET_DIR").map(PathBuf::from) {
let to_test = dir
.parent()
.unwrap()
.parent()
.unwrap()
.join(&target)
.join("llvm/bin/llvm-config");
if Command::new(&to_test).output().is_ok() {
return Some(to_test);
}
}
}
PathBuf::from("llvm-config")
});
None
});
if let Some(llvm_config) = &llvm_config {
println!("cargo:rerun-if-changed={}", llvm_config.display());
}
let llvm_config = llvm_config.unwrap_or_else(|| PathBuf::from("llvm-config"));
println!("cargo:rerun-if-changed={}", llvm_config.display());
println!("cargo:rerun-if-env-changed=LLVM_CONFIG");
// Test whether we're cross-compiling LLVM. This is a pretty rare case