libbpf-cargo: Add --clang-args argument to build and make sub-commands

With commit beff188 ("examples: Use vmlinux.h for current
architecture") we are having a hard time compiling the examples using
the cargo-libbpf command, because the vmlinux.h header file cannot be
found.
Introduce the --clang-args argument to allow for passing in additional
options -- such as an include path -- to the clang invocation. This
would also have helped with #337.

Signed-off-by: Daniel Müller <[email protected]>

Author: d-e-s-o

libbpf-cargo/CHANGELOG.md

@@ -4,6 +4,7 @@ Unreleased
   feature
 - Adjusted `SkeletonBuilder::clang_args` to accept an iterator of
   arguments instead of a string
+- Added `--clang-args` argument to `make` and `build` sub-commands
 - Updated `libbpf-sys` dependency to `1.3.0`
 - Bumped minimum Rust version to `1.70`
 

libbpf-cargo/src/build.rs

@@ -223,13 +223,18 @@ fn compile_one(
     strip_dwarf_info(out).with_context(|| format!("Failed to strip object file {}", out.display()))
 }
 
-fn compile(debug: bool, objs: &[UnprocessedObj], clang: &Path, target_dir: &Path) -> Result<()> {
+fn compile(
+    debug: bool,
+    objs: &[UnprocessedObj],
+    clang: &Path,
+    mut clang_args: Vec<OsString>,
+    target_dir: &Path,
+) -> Result<()> {
     let header_dir = extract_libbpf_headers_to_disk(target_dir)?;
-    let compiler_options = if let Some(dir) = &header_dir {
-        vec![OsString::from(format!("-I{}", dir.to_str().unwrap()))]
-    } else {
-        Vec::new()
-    };
+    if let Some(dir) = header_dir {
+        clang_args.push(OsString::from("-I"));
+        clang_args.push(dir.into_os_string());
+    }
 
     for obj in objs {
         let stem = obj.path.file_stem().with_context(|| {
@@ -245,7 +250,7 @@ fn compile(debug: bool, objs: &[UnprocessedObj], clang: &Path, target_dir: &Path
         let mut dest_path = obj.out.to_path_buf();
         dest_path.push(&dest_name);
         fs::create_dir_all(&obj.out)?;
-        compile_one(debug, &obj.path, &dest_path, clang, &compiler_options)?;
+        compile_one(debug, &obj.path, &dest_path, clang, &clang_args)?;
     }
 
     Ok(())
@@ -259,10 +264,12 @@ fn extract_clang_or_default(clang: Option<&PathBuf>) -> PathBuf {
     }
 }
 
+#[allow(clippy::too_many_arguments)]
 pub fn build(
     debug: bool,
     manifest_path: Option<&PathBuf>,
     clang: Option<&PathBuf>,
+    clang_args: Vec<OsString>,
     skip_clang_version_checks: bool,
 ) -> Result<()> {
     let (target_dir, to_compile) = metadata::get(debug, manifest_path)?;
@@ -281,7 +288,8 @@ pub fn build(
     let clang = extract_clang_or_default(clang);
     check_clang(debug, &clang, skip_clang_version_checks)
         .with_context(|| anyhow!("{} is invalid", clang.display()))?;
-    compile(debug, &to_compile, &clang, &target_dir).context("Failed to compile progs")?;
+    compile(debug, &to_compile, &clang, clang_args, &target_dir)
+        .context("Failed to compile progs")?;
 
     Ok(())
 }

libbpf-cargo/src/main.rs

@@ -1,6 +1,7 @@
 #![allow(clippy::let_unit_value)]
 #![warn(clippy::absolute_paths)]
 
+use std::ffi::OsString;
 use std::path::PathBuf;
 
 use anyhow::Result;
@@ -49,6 +50,9 @@ pub struct ClangOpts {
     /// Path to clang binary
     #[arg(long, value_parser)]
     clang_path: Option<PathBuf>,
+    /// Additional arguments to pass to `clang`.
+    #[arg(long, value_parser)]
+    clang_args: Vec<OsString>,
     /// Skip clang version checks
     #[arg(long)]
     skip_clang_version_checks: bool,
@@ -112,12 +116,14 @@ fn main() -> Result<()> {
                 clang_opts:
                     ClangOpts {
                         clang_path,
+                        clang_args,
                         skip_clang_version_checks,
                     },
             } => build::build(
                 debug,
                 manifest_path.as_ref(),
                 clang_path.as_ref(),
+                clang_args,
                 skip_clang_version_checks,
             ),
             Command::Gen {
@@ -135,6 +141,7 @@ fn main() -> Result<()> {
                 clang_opts:
                     ClangOpts {
                         clang_path,
+                        clang_args,
                         skip_clang_version_checks,
                     },
                 quiet,
@@ -144,6 +151,7 @@ fn main() -> Result<()> {
                 debug,
                 manifest_path.as_ref(),
                 clang_path.as_ref(),
+                clang_args,
                 skip_clang_version_checks,
                 quiet,
                 cargo_build_args,

libbpf-cargo/src/make.rs

@@ -1,3 +1,4 @@
+use std::ffi::OsString;
 use std::path::PathBuf;
 use std::process::Command;
 
@@ -8,10 +9,12 @@ use anyhow::Result;
 use crate::build;
 use crate::gen;
 
+#[allow(clippy::too_many_arguments)]
 pub fn make(
     debug: bool,
     manifest_path: Option<&PathBuf>,
     clang: Option<&PathBuf>,
+    clang_args: Vec<OsString>,
     skip_clang_version_checks: bool,
     quiet: bool,
     cargo_build_args: Vec<String>,
@@ -20,8 +23,14 @@ pub fn make(
     if !quiet {
         println!("Compiling BPF objects");
     }
-    build::build(debug, manifest_path, clang, skip_clang_version_checks)
-        .context("Failed to compile BPF objects")?;
+    build::build(
+        debug,
+        manifest_path,
+        clang,
+        clang_args,
+        skip_clang_version_checks,
+    )
+    .context("Failed to compile BPF objects")?;
 
     if !quiet {
         println!("Generating skeletons");