Clean up JNI initialization

scripts/bootstrap/compile.sh

@@ -378,7 +378,7 @@ function build_jni() {
 
     # Keep this `find` command in sync with the `srcs` of
     # //src/main/native/windows:windows_jni
-    local srcs=$(find src/main/native/windows -name '*.cc' -o -name '*.h')
+    local srcs="src/main/native/common.cc $(find src/main/native/windows -name '*.cc' -o -name '*.h')"
     [ -n "$srcs" ] || fail "Could not find sources for Windows JNI library"
 
     # do not quote $srcs because we need to expand it to multiple args

src/main/java/com/google/devtools/build/lib/jni/JniLoader.java

@@ -124,6 +124,12 @@ private static void loadLibrary(String resourceName) throws IOException {
         }
       } catch (IOException e2) {
         // Nothing else we can do. Rely on "delete on exit" to try clean things up later on.
+        if (dir != null) {
+          dir.toFile().deleteOnExit();
+        }
+        if (tempFile != null) {
+          tempFile.toFile().deleteOnExit();
+        }
       }
       throw e;
     }
@@ -153,4 +159,20 @@ public static boolean isJniAvailable() {
   public static Throwable getJniLoadError() {
     return JNI_LOAD_ERROR;
   }
+
+  /**
+   * Forcibly link a native method to eagerly trigger an {@link UnsatisfiedLinkError} in case of
+   * issues with the JNI library.
+   */
+  public static void forceLinking() throws UnsatisfiedLinkError {
+    if (isJniAvailable()) {
+      ForceLinkingHelper.link();
+    }
+  }
+
+  private static final class ForceLinkingHelper {
+    private static native void link();
+
+    private ForceLinkingHelper() {}
+  }
 }

src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java

@@ -98,7 +98,6 @@
 import com.google.devtools.build.lib.util.InterruptedFailureDetails;
 import com.google.devtools.build.lib.util.LoggingUtil;
 import com.google.devtools.build.lib.util.Pair;
-import com.google.devtools.build.lib.util.ProcessUtils;
 import com.google.devtools.build.lib.util.StringEncoding;
 import com.google.devtools.build.lib.util.TestType;
 import com.google.devtools.build.lib.util.ThreadUtils;
@@ -873,7 +872,8 @@ public static void main(Iterable<Class<? extends BlazeModule>> moduleClasses, St
       System.exit(batchMain(modules, args));
     }
     logger.atInfo().log(
-        "Starting Bazel server with %s, args %s", maybeGetPidString(), Arrays.toString(args));
+        "Starting Bazel server with pid %d, args %s",
+        ProcessHandle.current().pid(), Arrays.toString(args));
     try {
       // Run Blaze in server mode.
       System.exit(serverMain(modules, OutErr.SYSTEM_OUT_ERR, args));
@@ -1027,8 +1027,8 @@ private static int batchMain(Iterable<BlazeModule> modules, String[] args) {
     InterruptSignalHandler signalHandler = captureSigint(getSlowInterruptMessageSuffix(modules));
     CommandLineOptions commandLineOptions = splitStartupOptions(modules, args);
     logger.atInfo().log(
-        "Running Bazel in batch mode with %s, startup args %s",
-        maybeGetPidString(), commandLineOptions.getStartupArgs());
+        "Running Bazel in batch mode with pid %d, startup args %s",
+        ProcessHandle.current().pid(), commandLineOptions.getStartupArgs());
 
     BlazeRuntime runtime;
     InvocationPolicy policy;
@@ -1275,7 +1275,9 @@ private static BlazeRuntime newRuntime(
     PathFragment outputBase = startupOptions.outputBase;
     PathFragment realExecRootBase = outputBase.getRelative(ServerDirectories.EXECROOT);
 
-    maybeForceJNIByGettingPid(installBase); // Must be before first use of JNI.
+    // Force JNI linking before the first real use of JNI to emit a helpful error message now that
+    // we have the install base path handy.
+    forceJniLinking(installBase);
 
     // From the point of view of the Java program --install_base, --output_base, --output_user_root,
     // and --failure_detail_out are mandatory options, despite the comment in their declarations.
@@ -1462,32 +1464,17 @@ private static AbruptExitException createFilesystemExitException(
         e);
   }
 
-  private static String maybeGetPidString() {
-    Integer pid = maybeForceJNIByGettingPid(null);
-    return pid == null ? "" : "pid " + pid + " and ";
-  }
-
-  /** Loads JNI libraries, if necessary under the current platform. */
-  @Nullable
-  private static Integer maybeForceJNIByGettingPid(@Nullable PathFragment installBase) {
-    return JniLoader.isJniAvailable() ? getPidUsingJNI(installBase) : null;
-  }
-
-  // Force JNI linking at a moment when we have 'installBase' handy, and print
-  // an informative error if it fails.
-  private static int getPidUsingJNI(@Nullable PathFragment installBase) {
+  /**
+   * Loads and links JNI libraries, if necessary under the current platform, and prints an
+   * informative error to stderr if that fails.
+   */
+  private static void forceJniLinking(PathFragment installBase) {
     try {
-      return ProcessUtils.getpid(); // force JNI initialization
+      JniLoader.forceLinking();
     } catch (UnsatisfiedLinkError t) {
-      System.err.println(
-          "JNI initialization failed: "
-              + t.getMessage()
-              + ".  "
-              + "Possibly your installation has been corrupted"
-              + (installBase == null
-                  ? ""
-                  : "; if this problem persists, try 'rm -fr " + installBase + "'")
-              + ".");
+      System.err.printf(
+          "JNI initialization failed: %s. Possibly your installation has been corrupted; if this problem persists, try 'rm -fr %s'.\n",
+          t.getMessage(), installBase);
       throw t;
     }
   }

src/main/java/com/google/devtools/build/lib/unix/ProcessUtils.java

@@ -33,13 +33,6 @@ private ProcessUtils() {}
    */
   public static native int getgid();
 
-  /**
-   * Native wrapper around POSIX getpid(2) syscall.
-   *
-   * @return the process ID of this process.
-   */
-  public static native int getpid();
-
   /**
    * Native wrapper around POSIX getuid(2).
    *

src/main/java/com/google/devtools/build/lib/util/ProcessUtils.java

@@ -15,10 +15,12 @@
 package com.google.devtools.build.lib.util;
 
 import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
-import com.google.devtools.build.lib.windows.WindowsProcesses;
 
 /**
  * OS Process related utilities.
+ *
+ * <p>Use {@link ProcessHandle#current()} and {@link ProcessHandle#pid()} to get the PID of the
+ * current process.
  */
 @ThreadSafe
 public final class ProcessUtils {
@@ -39,19 +41,6 @@ public static int getgid() {
     }
   }
 
-  /**
-   * @return the process ID of this process.
-   * @throws UnsatisfiedLinkError when JNI is not available.
-   */
-  public static int getpid() {
-    // TODO(ulfjack): Use ProcessHandle.current().getPid() here.
-    if (OS.getCurrent() == OS.WINDOWS) {
-      return WindowsProcesses.getpid();
-    } else {
-      return com.google.devtools.build.lib.unix.ProcessUtils.getpid();
-    }
-  }
-
   /**
    * @return the real user ID of the current process.
    * @throws UnsatisfiedLinkError when JNI is not available.

src/main/java/com/google/devtools/build/lib/windows/WindowsProcesses.java

@@ -15,6 +15,7 @@
 package com.google.devtools.build.lib.windows;
 
 import com.google.devtools.build.lib.jni.JniLoader;
+import java.io.InputStream;
 
 /** Process management on Windows. */
 public class WindowsProcesses {
@@ -145,7 +146,4 @@ public static long createProcess(
   public static native String processGetLastError(long process);
 
   public static native String streamGetLastError(long process);
-
-  /** Returns the PID of the current process. */
-  public static native int getpid();
 }

src/main/native/BUILD

@@ -57,6 +57,18 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "common",
+    srcs = [
+        "common.cc",
+        ":jni.h",
+        ":jni_md.h",
+    ],
+    includes = ["."],  # For jni headers.
+    visibility = ["//src/main/native:__subpackages__"],
+    alwayslink = 1,
+)
+
 cc_library(
     name = "blake3_jni",
     srcs = [
@@ -99,6 +111,7 @@ cc_binary(
     visibility = ["//src/main/java/com/google/devtools/build/lib/jni:__pkg__"],
     deps = [
         ":blake3_jni",
+        ":common",
         ":latin1_jni_path",
         "//src/main/cpp/util:logging",
         "//src/main/cpp/util:md5",

src/main/native/common.cc

@@ -0,0 +1,22 @@
+// Copyright 2025 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/main/native/jni.h"
+
+namespace blaze_jni {
+
+extern "C" JNIEXPORT void JNICALL
+Java_com_google_devtools_build_lib_jni_JniLoader_00024ForceLinkingHelper_link(JNIEnv *env) {}
+
+}  // namespace blaze_jni

src/main/native/process.cc

@@ -26,16 +26,6 @@ Java_com_google_devtools_build_lib_unix_ProcessUtils_getgid(JNIEnv *env, jclass
   return getgid();
 }
 
-/*
- * Class:     com.google.devtools.build.lib.unix.ProcessUtils
- * Method:    getpid
- * Signature: ()I
- */
-extern "C" JNIEXPORT jint JNICALL
-Java_com_google_devtools_build_lib_unix_ProcessUtils_getpid(JNIEnv *env, jclass clazz) {
-  return getpid();
-}
-
 /*
  * Class:     com.google.devtools.build.lib.unix.ProcessUtils
  * Method:    getuid

src/main/native/windows/BUILD

@@ -77,6 +77,7 @@ cc_binary(
         ":lib-file",
         ":lib-process",
         "//src/main/native:blake3_jni",
+        "//src/main/native:common",
     ],
 )
 

src/main/native/windows/processes-jni.cc

@@ -43,12 +43,6 @@ static std::wstring ToString(const T& e) {
   return s.str();
 }
 
-extern "C" JNIEXPORT jint JNICALL
-Java_com_google_devtools_build_lib_windows_WindowsProcesses_getpid(
-    JNIEnv* env, jclass clazz) {
-  return GetCurrentProcessId();
-}
-
 class JavaByteArray {
  public:
   JavaByteArray(JNIEnv* env, jbyteArray java_array)