taiki-e · taiki-e · Oct 4, 2025 · Oct 4, 2025
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -77,30 +77,40 @@ jobs:
       - run: cargo install --path . --debug
       - name: Test cargo llvm-cov nextest
         run: |
+          unset RUSTFLAGS
           cargo llvm-cov nextest --text --fail-under-lines 50
           cargo llvm-cov nextest --text --fail-under-lines 50 --profile default --cargo-profile dev
           cargo llvm-cov nextest --text --fail-under-lines 50 --profile ci
           cargo llvm-cov nextest --text --fail-under-lines 50 --profile ci --cargo-profile dev
+          cargo clean
           cd -- ../real1
           cargo llvm-cov nextest-archive --archive-file a.tar.zst
           cargo llvm-cov nextest --archive-file a.tar.zst --text --fail-under-lines 70
           cargo llvm-cov report --nextest-archive-file a.tar.zst --fail-under-lines 70
-          rm -- a.tar.zst
           cargo clean
+          rm -- a.tar.zst
           cargo llvm-cov nextest-archive --archive-file a.tar.zst --release
           cargo llvm-cov nextest --archive-file a.tar.zst --text --fail-under-lines 70
           cargo llvm-cov report --nextest-archive-file a.tar.zst --fail-under-lines 70
-          rm -- a.tar.zst
           cargo clean
+          rm -- a.tar.zst
           cargo llvm-cov nextest-archive --archive-file a.tar.zst --cargo-profile custom
           cargo llvm-cov nextest --archive-file a.tar.zst --text --fail-under-lines 70
           cargo llvm-cov report --nextest-archive-file a.tar.zst --fail-under-lines 70
-          rm -- a.tar.zst
           cargo clean
+          rm -- a.tar.zst
           host=$(rustc -vV | grep -E '^host:' | cut -d' ' -f2)
           cargo llvm-cov nextest-archive --archive-file a.tar.zst --target "${host}"
           cargo llvm-cov nextest --archive-file a.tar.zst --text --fail-under-lines 70
           cargo llvm-cov report --nextest-archive-file a.tar.zst --fail-under-lines 70
+          cargo clean
+          rm -- a.tar.zst
+          cd -- ../build_dir
+          cargo llvm-cov nextest --text --fail-under-lines 100
+          cargo llvm-cov nextest --text --fail-under-lines 100 --profile default --cargo-profile dev
+          cargo llvm-cov nextest --text --fail-under-lines 100 --profile ci
+          cargo llvm-cov nextest --text --fail-under-lines 100 --profile ci --cargo-profile dev
+          cargo clean
         working-directory: tests/fixtures/crates/bin_crate
       - name: Test nightly-specific options, old Cargo compatibility, trybuild compatibility
         run: |

diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -12,7 +12,9 @@ Note: In this file, do not use the hard wrap in the middle of a sentence for com
 
 ## [Unreleased]
 
-- Update minimal version of `cargo-config2` to 0.1.38 to improve support for target names that contain ".". ([#446](https://github.com/taiki-e/cargo-llvm-cov/pull/446))
+- Support Cargo `build-dir` that added in Cargo 1.91. ([#452](https://github.com/taiki-e/cargo-llvm-cov/pull/452))
+
+- Update minimal version of `cargo-config2` to 0.1.38 to improve support for target names that contain ".". ([#446](https://github.com/taiki-e/cargo-llvm-cov/issues/446))
 
 ## [0.6.19] - 2025-09-07
 

diff --git a/README.md b/README.md
@@ -676,6 +676,7 @@ You may need to click the "Watch" label in the bottom bar of VS Code to display
 You can override these environment variables to change cargo-llvm-cov's behavior on your system:
 
 - `CARGO_LLVM_COV_TARGET_DIR` -- Location of where to place all generated artifacts, relative to the current working directory. Default to `<cargo_target_dir>/llvm-cov-target`.
+- `CARGO_LLVM_COV_BUILD_DIR` -- Location of where intermediate build artifacts will be stored, relative to the current working directory. Default to `<cargo_target_dir>/llvm-cov-target`.
 - `CARGO_LLVM_COV_SETUP` -- Control behavior if `llvm-tools-preview` component is not installed. See [#219] for more.
 - `LLVM_COV` -- Override the path to `llvm-cov`. You may need to specify both this and `LLVM_PROFDATA` environment variables if you are using [`--include-ffi` flag](#get-coverage-of-cc-code-linked-to-rust-librarybinary) or if you are using a toolchain installed without via rustup. `llvm-cov` version must be compatible with the LLVM version used in rustc.
 - `LLVM_PROFDATA` -- Override the path to `llvm-profdata`. See `LLVM_COV` environment variable for more.

diff --git a/src/cargo.rs b/src/cargo.rs
@@ -7,7 +7,7 @@ use camino::{Utf8Path, Utf8PathBuf};
 use cargo_config2::Config;
 
 use crate::{
-    cli::{Args, ManifestOptions, Subcommand},
+    cli::{ManifestOptions, Subcommand},
     context::Context,
     env,
     metadata::Metadata,
@@ -21,6 +21,7 @@ pub(crate) struct Workspace {
     pub(crate) current_manifest: Utf8PathBuf,
 
     pub(crate) target_dir: Utf8PathBuf,
+    pub(crate) build_dir: Option<Utf8PathBuf>,
     pub(crate) output_dir: Utf8PathBuf,
     pub(crate) doctests_dir: Utf8PathBuf,
     pub(crate) profdata_file: Utf8PathBuf,
@@ -92,18 +93,32 @@ impl Workspace {
                 .is_ok_and(|s| s.contains("doctest-in-workspace"));
         }
 
-        let target_dir =
-            if let Some(path) = env::var("CARGO_LLVM_COV_TARGET_DIR")?.map(Utf8PathBuf::from) {
-                let mut base: Utf8PathBuf = env::current_dir()?.try_into()?;
-                base.push(path);
+        let (target_dir, build_dir) = if let Some(mut target_dir) =
+            env::var("CARGO_LLVM_COV_TARGET_DIR")?.map(Utf8PathBuf::from)
+        {
+            let mut base: Utf8PathBuf = env::current_dir()?.try_into()?;
+            target_dir = base.join(target_dir);
+            let build_dir = if let Some(build_dir) =
+                env::var("CARGO_LLVM_COV_BUILD_DIR")?.map(Utf8PathBuf::from)
+            {
+                base.push(build_dir);
                 base
-            } else if show_env {
-                metadata.target_directory.clone()
             } else {
-                // If we change RUSTFLAGS, all dependencies will be recompiled. Therefore,
-                // use a subdirectory of the target directory as the actual target directory.
-                metadata.target_directory.join("llvm-cov-target")
+                target_dir.clone()
             };
+            (target_dir, build_dir)
+        } else if show_env {
+            (metadata.target_directory.clone(), metadata.build_directory().to_owned())
+        } else {
+            // If we change RUSTFLAGS, all dependencies will be recompiled. Therefore,
+            // use a subdirectory of the target directory as the actual target directory.
+            (
+                metadata.target_directory.join("llvm-cov-target"),
+                metadata.build_directory().join("llvm-cov-target"),
+            )
+        };
+        // The scope of --target-dir's effect depends on whether build-dir is specified in the config.
+        let build_dir = config.build.build_dir.as_ref().and(Some(build_dir));
         let output_dir = metadata.target_directory.join("llvm-cov");
         let doctests_dir = target_dir.join("doctestbins");
 
@@ -116,6 +131,7 @@ impl Workspace {
             metadata,
             current_manifest,
             target_dir,
+            build_dir,
             output_dir,
             doctests_dir,
             profdata_file,
@@ -222,7 +238,16 @@ pub(crate) fn test_or_run_args(cx: &Context, cmd: &mut ProcessBuilder) {
     cmd.arg("--manifest-path");
     cmd.arg(&cx.ws.current_manifest);
 
-    add_target_dir(&cx.args, cmd, &cx.ws.target_dir);
+    // https://github.com/taiki-e/cargo-llvm-cov/issues/265
+    if matches!(cx.args.subcommand, Subcommand::Nextest { archive_file: true }) {
+        cmd.arg("--extract-to");
+    } else {
+        cmd.arg("--target-dir");
+    }
+    cmd.arg(cx.ws.target_dir.as_str());
+    if let Some(build_dir) = &cx.ws.build_dir {
+        cmd.env("CARGO_BUILD_BUILD_DIR", build_dir.as_str());
+    }
 
     for cargo_arg in &cx.args.cargo_args {
         cmd.arg(cargo_arg);
@@ -257,6 +282,9 @@ pub(crate) fn clean_args(cx: &Context, cmd: &mut ProcessBuilder) {
 
     cmd.arg("--target-dir");
     cmd.arg(cx.ws.target_dir.as_str());
+    if let Some(build_dir) = &cx.ws.build_dir {
+        cmd.env("CARGO_BUILD_BUILD_DIR", build_dir.as_str());
+    }
 
     cx.args.manifest.cargo_args(cmd);
 
@@ -265,13 +293,3 @@ pub(crate) fn clean_args(cx: &Context, cmd: &mut ProcessBuilder) {
         cmd.arg(format!("-{}", "v".repeat(cx.args.verbose as usize - 1)));
     }
 }
-
-// https://github.com/taiki-e/cargo-llvm-cov/issues/265
-fn add_target_dir(args: &Args, cmd: &mut ProcessBuilder, target_dir: &Utf8Path) {
-    if matches!(args.subcommand, Subcommand::Nextest { archive_file: true }) {
-        cmd.arg("--extract-to");
-    } else {
-        cmd.arg("--target-dir");
-    }
-    cmd.arg(target_dir.as_str());
-}
diff --git a/src/clean.rs b/src/clean.rs
@@ -29,6 +29,9 @@ pub(crate) fn run(args: &mut Args) -> Result<()> {
         for dir in &[&ws.target_dir, &ws.output_dir] {
             rm_rf(dir, args.verbose != 0)?;
         }
+        if let Some(dir) = &ws.build_dir {
+            rm_rf(dir, args.verbose != 0)?;
+        }
         return Ok(());
     }
 
@@ -92,6 +95,9 @@ fn clean_ws(
     for args in args_set {
         let mut cmd = ws.cargo(verbose);
         cmd.args(["clean", "--target-dir", ws.target_dir.as_str()]).args(&package_args);
+        if let Some(build_dir) = &ws.build_dir {
+            cmd.env("CARGO_BUILD_BUILD_DIR", build_dir.as_str());
+        }
         cmd.args(args);
         if verbose > 0 {
             cmd.arg(format!("-{}", "v".repeat(verbose as usize)));

diff --git a/src/context.rs b/src/context.rs
@@ -127,6 +127,14 @@ impl Context {
                 if args.subcommand.call_cargo_nextest() { "cargo-nextest" } else { "cargo" }
             );
         }
+        if ws.config.build.build_dir.is_some()
+            && matches!(
+                args.subcommand,
+                Subcommand::Nextest { archive_file: true } | Subcommand::NextestArchive
+            )
+        {
+            warn!("nextest archive may not work with Cargo build-dir");
+        }
 
         let (llvm_cov, llvm_profdata): (PathBuf, PathBuf) = match (
             env::var_os("LLVM_COV").map(PathBuf::from),

diff --git a/src/main.rs b/src/main.rs
@@ -82,6 +82,7 @@ fn try_main() -> Result<()> {
             };
             set_env(cx, writer, IsNextest(true))?; // Include envs for nextest.
             writer.set("CARGO_LLVM_COV_TARGET_DIR", cx.ws.metadata.target_directory.as_str())?;
+            writer.set("CARGO_LLVM_COV_BUILD_DIR", cx.ws.metadata.build_directory().as_str())?;
             writer.writer.flush()?;
         }
         Subcommand::Report { .. } => {
@@ -791,8 +792,10 @@ fn object_files(cx: &Context) -> Result<Vec<OsString>> {
     // This is not the ideal way, but the way unstable book says it is cannot support them.
     // https://doc.rust-lang.org/nightly/rustc/instrument-coverage.html#tips-for-listing-the-binaries-automatically
     let mut target_dir = cx.ws.target_dir.clone();
+    let mut build_dir = cx.ws.build_dir.clone();
     let mut auto_detect_profile = false;
     if cx.args.subcommand.read_nextest_archive() {
+        // TODO: build-dir
         #[derive(Debug, Deserialize)]
         #[serde(rename_all = "kebab-case")]
         struct BinariesMetadata {
@@ -852,9 +855,12 @@ fn object_files(cx: &Context) -> Result<Vec<OsString>> {
         }
     }
     if !auto_detect_profile {
-        // https://doc.rust-lang.org/nightly/cargo/guide/build-cache.html
+        // https://doc.rust-lang.org/nightly/cargo/reference/build-cache.html
         if let Some(target) = &cx.args.target {
             target_dir.push(target);
+            if let Some(build_dir) = &mut build_dir {
+                build_dir.push(target);
+            }
         }
         // https://doc.rust-lang.org/nightly/cargo/reference/profiles.html#custom-profiles
         let profile = match cx.args.cargo_profile.as_deref() {
@@ -864,6 +870,9 @@ fn object_files(cx: &Context) -> Result<Vec<OsString>> {
             Some(p) => p,
         };
         target_dir.push(profile);
+        if let Some(build_dir) = &mut build_dir {
+            build_dir.push(profile);
+        }
     }
     for f in walk_target_dir(cx, &target_dir) {
         let f = f.path();
@@ -876,6 +885,22 @@ fn object_files(cx: &Context) -> Result<Vec<OsString>> {
         }
     }
     searched_dir.push_str(target_dir.as_str());
+    if let Some(build_dir) = &build_dir {
+        if target_dir != *build_dir {
+            for f in walk_target_dir(cx, build_dir) {
+                let f = f.path();
+                if is_object(cx, f) {
+                    if let Some(file_stem) = fs::file_stem_recursive(f).unwrap().to_str() {
+                        if re.is_match(file_stem) {
+                            files.push(make_relative(cx, f).to_owned().into_os_string());
+                        }
+                    }
+                }
+            }
+            searched_dir.push(',');
+            searched_dir.push_str(build_dir.as_str());
+        }
+    }
     if cx.args.doctests {
         for f in glob::glob(
             Utf8Path::new(&glob::Pattern::escape(cx.ws.doctests_dir.as_str()))
@@ -931,10 +956,10 @@ fn object_files(cx: &Context) -> Result<Vec<OsString>> {
     files.sort_unstable();
 
     if files.is_empty() {
-        warn!(
+        bail!(
             "not found object files (searched directories: {searched_dir}); this may occur if \
              show-env subcommand is used incorrectly (see docs or other warnings), or unsupported \
-             commands are used",
+             commands or configs are used",
         );
     }
     Ok(files)
@@ -1313,6 +1338,11 @@ fn ignore_filename_regex(cx: &Context, object_files: &[OsString]) -> Result<Opti
                 ));
             }
             out.push_abs_path(&cx.ws.target_dir);
+            if let Some(build_dir) = &cx.ws.build_dir {
+                if *build_dir != cx.ws.target_dir {
+                    out.push_abs_path(build_dir);
+                }
+            }
             if cx.args.remap_path_prefix {
                 if let Some(path) = env::home_dir() {
                     out.push_abs_path(path);

diff --git a/src/metadata.rs b/src/metadata.rs
@@ -5,7 +5,7 @@
 use std::{collections::HashMap, ffi::OsStr, path::Path};
 
 use anyhow::{Context as _, Result, format_err};
-use camino::Utf8PathBuf;
+use camino::{Utf8Path, Utf8PathBuf};
 use serde_json::{Map, Value};
 
 type Object = Map<String, Value>;
@@ -33,6 +33,8 @@ pub(crate) struct Metadata {
     /// The absolute path to the root of the workspace.
     pub(crate) workspace_root: Utf8PathBuf,
     pub(crate) target_directory: Utf8PathBuf,
+    /// This is always `None` if running with a version of Cargo older than 1.91.
+    build_directory: Option<Utf8PathBuf>,
 }
 
 impl Metadata {
@@ -67,8 +69,18 @@ impl Metadata {
             workspace_members,
             workspace_root: map.remove_string("workspace_root")?,
             target_directory: map.remove_string("target_directory")?,
+            // This field was added in Rust 1.91.
+            build_directory: if map.contains_key("build_directory") {
+                Some(map.remove_string("build_directory")?)
+            } else {
+                None
+            },
         })
     }
+
+    pub(crate) fn build_directory(&self) -> &Utf8Path {
+        self.build_directory.as_deref().unwrap_or(&self.target_directory)
+    }
 }
 
 pub(crate) struct Package {
@@ -110,11 +122,7 @@ impl Target {
 
 // #[allow(clippy::option_option)]
 // fn allow_null<T>(value: Value, f: impl FnOnce(Value) -> Option<T>) -> Option<Option<T>> {
-//     if value.is_null() {
-//         Some(None)
-//     } else {
-//         f(value).map(Some)
-//     }
+//     if value.is_null() { Some(None) } else { f(value).map(Some) }
 // }
 
 fn into_string<S: From<String>>(value: Value) -> Option<S> {

diff --git a/tests/fixtures/coverage-reports/build_dir/build_dir.codecov.json b/tests/fixtures/coverage-reports/build_dir/build_dir.codecov.json
@@ -0,0 +1 @@
+{"coverage":{"src/lib.rs":{"1":"1/1","2":"2/3","3":"1/1","6":"1/1","10":"2/2","11":"1/1"}}}
diff --git a/tests/fixtures/coverage-reports/build_dir/build_dir.hide-instantiations.txt b/tests/fixtures/coverage-reports/build_dir/build_dir.hide-instantiations.txt
@@ -0,0 +1,12 @@
+    1|      1|fn func(x: i32) -> bool {
+    2|      1|    if x < 0 { true } else { false }
+                                           ^0
+    3|      1|}
+    4|       |
+    5|       |#[test]
+    6|      1|fn test() {
+    7|       |    #[cfg(a)]
+    8|       |    assert!(!func(1));
+    9|       |    #[cfg(not(a))]
+   10|      1|    assert!(func(-1));
+   11|      1|}
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		{"coverage":{"src/lib.rs":{"1":"1/1","2":"2/3","3":"1/1","6":"1/1","10":"2/2","11":"1/1"}}}