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Only add typical CUDA paths to the linker search paths if no explicit path is supplied #475

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Merged
chelsea0x3b merged 3 commits into from
Oct 30, 2025
Merged

Only add typical CUDA paths to the linker search paths if no explicit path is supplied #475

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Only add typical locations to the linker search paths if no explicit …
johanpel Oct 30, 2025
e8cbeba
Clippy
johanpel Oct 30, 2025
af73f30
Apply suggestion from @coreylowman
chelsea0x3b Oct 30, 2025
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53 changes: 35 additions & 18 deletions build.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,13 @@
use std::path::PathBuf;

const TYPICAL_CUDA_PATH_ENV_VARS: [&'static str; 5] = [

Check failure on line 3 in build.rs

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constants have by default a `'static` lifetime
"CUDA_HOME",
"CUDA_PATH",
"CUDA_ROOT",
"CUDA_TOOLKIT_ROOT_DIR",
"CUDNN_LIB",
];

fn main() {
#[cfg(all(
not(feature = "dynamic-linking"),
Expand All @@ -15,10 +23,10 @@
panic!("Both `dynamic-loading` and `dynamic-linking` features are active, this is a bug");

println!("cargo:rerun-if-changed=build.rs");
println!("cargo:rerun-if-env-changed=CUDA_ROOT");
println!("cargo:rerun-if-env-changed=CUDA_PATH");
println!("cargo:rerun-if-env-changed=CUDA_TOOLKIT_ROOT_DIR");
println!("cargo:rerun-if-env-changed=CUDARC_CUDA_VERSION");
TYPICAL_CUDA_PATH_ENV_VARS
.iter()
.for_each(|var| println!("cargo:rerun-if-env-changed={var}"));

let (major, minor): (usize, usize) = if let Ok(version) = std::env::var("CUDARC_CUDA_VERSION") {
let (major, minor) = match version.as_str() {
Expand Down Expand Up @@ -231,18 +239,22 @@

#[allow(unused)]
fn link_searches(major: usize, minor: usize) -> Vec<PathBuf> {
let env_vars = [
"CUDA_PATH",
"CUDA_ROOT",
"CUDA_TOOLKIT_ROOT_DIR",
"CUDNN_LIB",
];
let env_vars = env_vars
.into_iter()
let env_vars = TYPICAL_CUDA_PATH_ENV_VARS
.iter()
.map(std::env::var)
.filter_map(Result::ok);
.filter_map(Result::ok)
.collect::<Vec<_>>();
Comment on lines +242 to +246

@gemini-code-assist gemini-code-assist Bot Oct 30, 2025

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high

Collecting the environment variables into a Vec here is inefficient as it forces an allocation. The subsequent logic then requires another allocation if no environment variables are found. This can be made more performant and idiomatic by using iterators.

Consider refactoring this part of link_searches to use a peekable() iterator and a trait object (Box<dyn Iterator<...>>) to avoid allocations:

// In link_searches function
let mut env_vars_iter = TYPICAL_CUDA_PATH_ENV_VARS
    .iter()
    .map(std::env::var)
    .filter_map(Result::ok)
    .peekable();

let no_env_vars = env_vars_iter.peek().is_none();

// ... conda warning logic using `no_env_vars` ...

let roots_iter: Box<dyn Iterator<Item = PathBuf>> = if no_env_vars {
    Box::new(typical_locations.into_iter().map(PathBuf::from))
} else {
    Box::new(env_vars_iter.map(PathBuf::from))
};

for root in roots_iter {
    // ... existing loop body
}

This approach avoids intermediate collections, reducing memory allocations and making the code cleaner.


// When building in a Conda-like environment with dynamic linking, if no
// CUDA path is supplied, then it is higly likely that, by defaulting our
// linker search paths to the typical locations below, linker errors will
// occur. Print a warning with some guidance.
#[cfg(feature = "dynamic-linking")]
if env_vars.is_empty() && std::env::var("CONDA_PREFIX").is_ok() {
println!("cargo::warning=Detected CONDA_PREFIX in the environment, but no CUDA path was set through one of: {TYPICAL_CUDA_PATH_ENV_VARS:?}. Linker errors are likely to occur. Please ensure the environment contains all required dependencies (e.g. the \"cuda-driver-dev\") and retry building with CUDA_HOME=$CONDA_PREFIX.")
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}

let standard_locations = [
let typical_locations = [
"/usr",
"/usr/local/cuda",
"/opt/cuda",
Expand All @@ -264,13 +276,18 @@
"C:/Program Files/NVIDIA/CUDNN/v9.1",
"C:/Program Files/NVIDIA/CUDNN/v9.0",
];
let standard_locations = standard_locations.into_iter().map(Into::into);

let possible_locations = if env_vars.is_empty() {
typical_locations
.into_iter()
.map(Into::<String>::into)
.collect()
} else {
env_vars
};

let mut candidates = Vec::new();
for root in env_vars
.chain(standard_locations)
.map(Into::<PathBuf>::into)
{
for root in possible_locations.into_iter().map(Into::<PathBuf>::into) {
candidates.extend(
[
"lib".into(),
Expand Down
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