bazelbuild · jjudd · Dec 13, 2025 · Dec 14, 2025
@@ -22,7 +22,11 @@ function download_and_check_hash() {
    TMP_FILE=$(mktemp -q /tmp/remotejavatools.XXXXXX)
    echo "fetching $name from $url to ${TMP_FILE}"
    curl --silent -o ${TMP_FILE} -L "$url"
-    actual_hash=`sha256sum ${TMP_FILE} | cut -d' ' -f1`
+    if command -v sha256sum &> /dev/null; then
+        actual_hash=`sha256sum ${TMP_FILE} | cut -d' ' -f1`
+    else
+        actual_hash=`shasum -a 256 ${TMP_FILE} | cut -d' ' -f1`
+    fi
    if [ "${hash}" != "${actual_hash}" ]; then
      echo "ERROR: wrong hash for ${name}! wanted: ${hash}, got: ${actual_hash}"
      exit 1

@@ -129,29 +129,35 @@ def _bootclasspath_impl(ctx):
    exec_javabase = ctx.attr.java_runtime_alias[java_common.JavaRuntimeInfo]
    env = ctx.attr._utf8_environment[Utf8EnvironmentInfo].environment

-    class_dir = ctx.actions.declare_directory("%s_classes" % ctx.label.name)
-
-    args = ctx.actions.args()
-    args.add("-source")
-    args.add("8")
-    args.add("-target")
-    args.add("8")
-    args.add("-Xlint:-options")
-    args.add("-J-XX:-UsePerfData")
-    args.add("-d")
-    args.add_all([class_dir], expand_directories = False)
-    args.add(ctx.file.src)
-
-    ctx.actions.run(
-        executable = "%s/bin/javac" % exec_javabase.java_home,
-        mnemonic = "JavaToolchainCompileClasses",
-        inputs = [ctx.file.src] + ctx.files.java_runtime_alias,
-        outputs = [class_dir],
-        arguments = [args],
-        env = env,
-        execution_requirements = _SUPPORTS_PATH_MAPPING,
-        use_default_shell_env = True,
-    )
+    # If possible, use JDK 11+'s ability to run a single Java file to avoid a
+    # separate action to compile DumpPlatformClassPath.
+    use_source_launcher = exec_javabase.version >= 11
+
+    class_dir = None
+    if not use_source_launcher:
+        class_dir = ctx.actions.declare_directory("%s_classes" % ctx.label.name)
+
+        args = ctx.actions.args()
+        args.add("-source")
+        args.add("8")
+        args.add("-target")
+        args.add("8")
+        args.add("-Xlint:-options")
+        args.add("-J-XX:-UsePerfData")
+        args.add("-d")
+        args.add_all([class_dir], expand_directories = False)
+        args.add(ctx.file.src)
+
+        ctx.actions.run(
+            executable = "%s/bin/javac" % exec_javabase.java_home,
+            mnemonic = "JavaToolchainCompileClasses",
+            inputs = [ctx.file.src] + ctx.files.java_runtime_alias,
+            outputs = [class_dir],
+            arguments = [args],
+            env = env,
+            execution_requirements = _SUPPORTS_PATH_MAPPING,
+            use_default_shell_env = True,
+        )

    unstripped_bootclasspath = ctx.actions.declare_file("%s_unstripped.jar" % ctx.label.name)

@@ -161,8 +167,13 @@ def _bootclasspath_impl(ctx):
    args.add("--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED")
    args.add("--add-exports=jdk.compiler/com.sun.tools.javac.platform=ALL-UNNAMED")
    args.add("--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED")
-    args.add_all("-cp", [class_dir], expand_directories = False)
-    args.add("DumpPlatformClassPath")
+
+    if use_source_launcher:
+        args.add(ctx.file.src)
+    else:
+        args.add_all("-cp", [class_dir], expand_directories = False)
+        args.add("DumpPlatformClassPath")
+
    args.add(unstripped_bootclasspath)

    if ctx.attr.language_version_bootstrap_runtime:
@@ -211,7 +222,8 @@ Rerun with --toolchain_resolution_debug='@bazel_tools//tools/jdk:bootstrap_runti
    if len(system) != len(system_files):
        system = None

-    inputs = depset([class_dir] + ctx.files.java_runtime_alias, transitive = [any_javabase.files])
+    classpath_input = ctx.file.src if use_source_launcher else class_dir
+    inputs = depset([classpath_input] + ctx.files.java_runtime_alias, transitive = [any_javabase.files])
    ctx.actions.run(
        executable = str(exec_javabase.java_executable_exec_path),
        mnemonic = "JavaToolchainCompileBootClasspath",