Replace magic constants with named exit codes

Author: DSouzaM

substratevm/src/com.oracle.svm.agent/src/com/oracle/svm/agent/NativeImageAgent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -24,6 +24,11 @@
  */
 package com.oracle.svm.agent;
 
+import static com.oracle.svm.agent.NativeImageAgent.ExitCodes.AGENT_ERROR;
+import static com.oracle.svm.agent.NativeImageAgent.ExitCodes.PARSE_ERROR;
+import static com.oracle.svm.agent.NativeImageAgent.ExitCodes.SUCCESS;
+import static com.oracle.svm.agent.NativeImageAgent.ExitCodes.USAGE_ERROR;
+
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.nio.file.AtomicMoveNotSupportedException;
@@ -154,12 +159,12 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
         for (String token : tokens) {
             if (token.startsWith("trace-output=")) {
                 if (traceOutputFile != null) {
-                    return usage(1, "cannot specify trace-output= more than once.");
+                    return usage("cannot specify trace-output= more than once.");
                 }
                 traceOutputFile = getTokenValue(token);
             } else if (token.startsWith("config-output-dir=") || token.startsWith("config-merge-dir=")) {
                 if (configOutputDir != null) {
-                    return usage(1, "cannot specify more than one of config-output-dir= or config-merge-dir=.");
+                    return usage("cannot specify more than one of config-output-dir= or config-merge-dir=.");
                 }
                 configOutputDir = transformPath(getTokenValue(token));
                 if (token.startsWith("config-merge-dir=")) {
@@ -197,12 +202,12 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
             } else if (token.startsWith("config-write-period-secs=")) {
                 configWritePeriod = parseIntegerOrNegative(getTokenValue(token));
                 if (configWritePeriod <= 0) {
-                    return usage(1, "config-write-period-secs must be an integer greater than 0");
+                    return usage("config-write-period-secs must be an integer greater than 0");
                 }
             } else if (token.startsWith("config-write-initial-delay-secs=")) {
                 configWritePeriodInitialDelay = parseIntegerOrNegative(getTokenValue(token));
                 if (configWritePeriodInitialDelay < 0) {
-                    return usage(1, "config-write-initial-delay-secs must be an integer greater or equal to 0");
+                    return usage("config-write-initial-delay-secs must be an integer greater or equal to 0");
                 }
             } else if (isBooleanOption(token, "experimental-configuration-with-origins")) {
                 configurationWithOrigins = getBooleanTokenValue(token);
@@ -215,7 +220,7 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
             } else if (isBooleanOption(token, "track-reflection-metadata")) {
                 trackReflectionMetadata = getBooleanTokenValue(token);
             } else {
-                return usage(1, "unknown option: '" + token + "'.");
+                return usage("unknown option: '" + token + "'.");
             }
         }
 
@@ -225,7 +230,7 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
         }
 
         if (configurationWithOrigins && !conditionalConfigUserPackageFilterFiles.isEmpty()) {
-            return error(5, "The agent can only be used in either the configuration with origins mode or the predefined classes mode.");
+            return error(USAGE_ERROR, "The agent can only be used in either the configuration with origins mode or the predefined classes mode.");
         }
 
         if (configurationWithOrigins && !mergeConfigs.isEmpty()) {
@@ -250,20 +255,20 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
                 callerFilter = new ComplexFilter(callerFilterHierarchyFilterNode);
             }
             if (!parseFilterFiles(callerFilter, callerFilterFiles)) {
-                return 1;
+                return PARSE_ERROR;
             }
         }
 
         ComplexFilter accessFilter = null;
         if (!accessFilterFiles.isEmpty()) {
             accessFilter = new ComplexFilter(AccessAdvisor.copyBuiltinAccessFilterTree());
             if (!parseFilterFiles(accessFilter, accessFilterFiles)) {
-                return 1;
+                return PARSE_ERROR;
             }
         }
 
         if (!conditionalConfigUserPackageFilterFiles.isEmpty() && conditionalConfigPartialRun) {
-            return error(6, "The agent can generate conditional configuration either for the current run or in the partial mode but not both at the same time.");
+            return error(USAGE_ERROR, "The agent can generate conditional configuration either for the current run or in the partial mode but not both at the same time.");
         }
 
         boolean isConditionalConfigurationRun = !conditionalConfigUserPackageFilterFiles.isEmpty() || conditionalConfigPartialRun;
@@ -274,7 +279,7 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
 
         if (configOutputDir != null) {
             if (traceOutputFile != null) {
-                return usage(1, "can only once specify exactly one of trace-output=, config-output-dir= or config-merge-dir=.");
+                return usage("can only once specify exactly one of trace-output=, config-output-dir= or config-merge-dir=.");
             }
             try {
                 configOutputDirPath = Files.createDirectories(Path.of(configOutputDir));
@@ -289,7 +294,7 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
                     } catch (Exception ignored) {
                         process = "(unknown)";
                     }
-                    return error(2, "Output directory '" + configOutputDirPath + "' is locked by process " + process + ", " +
+                    return error(AGENT_ERROR, "Output directory '" + configOutputDirPath + "' is locked by process " + process + ", " +
                                     "which means another agent instance is already writing to this directory. " +
                                     "Only one agent instance can safely write to a specific target directory at the same time. " +
                                     "Unless file '" + ConfigurationFile.LOCK_FILE_NAME + "' is a leftover from an earlier process that terminated abruptly, it is unsafe to delete it. " +
@@ -322,13 +327,13 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
                         } else {
                             ComplexFilter userCodeFilter = new ComplexFilter(HierarchyFilterNode.createRoot());
                             if (!parseFilterFiles(userCodeFilter, conditionalConfigUserPackageFilterFiles)) {
-                                return 2;
+                                return PARSE_ERROR;
                             }
                             ComplexFilter classNameFilter;
                             if (!conditionalConfigClassNameFilterFiles.isEmpty()) {
                                 classNameFilter = new ComplexFilter(HierarchyFilterNode.createRoot());
                                 if (!parseFilterFiles(classNameFilter, conditionalConfigClassNameFilterFiles)) {
-                                    return 3;
+                                    return PARSE_ERROR;
                                 }
                             } else {
                                 classNameFilter = new ComplexFilter(HierarchyFilterNode.createInclusiveRoot());
@@ -360,16 +365,16 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
                 }
                 expectedConfigModifiedBefore = getMostRecentlyModified(configOutputDirPath, getMostRecentlyModified(configOutputLockFilePath, null));
             } catch (Throwable t) {
-                return error(2, t.toString());
+                return error(AGENT_ERROR, t.toString());
             }
-        } else if (traceOutputFile != null) {
+        } else {
             try {
                 Path path = Paths.get(transformPath(traceOutputFile));
                 TraceFileWriter writer = new TraceFileWriter(path);
                 tracer = writer;
                 tracingResultWriter = writer;
             } catch (Throwable t) {
-                return error(2, t.toString());
+                return error(AGENT_ERROR, t.toString());
             }
         }
 
@@ -381,16 +386,16 @@ protected int onLoadCallback(JNIJavaVM vm, JvmtiEnv jvmti, JvmtiEventCallbacks c
             BreakpointInterceptor.onLoad(jvmti, callbacks, tracer, this, interceptedStateSupplier,
                             experimentalClassLoaderSupport, experimentalClassDefineSupport, experimentalUnsafeAllocationSupport, trackReflectionMetadata);
         } catch (Throwable t) {
-            return error(3, t.toString());
+            return error(AGENT_ERROR, t.toString());
         }
         try {
             JniCallInterceptor.onLoad(tracer, this, interceptedStateSupplier);
         } catch (Throwable t) {
-            return error(4, t.toString());
+            return error(AGENT_ERROR, t.toString());
         }
 
         setupExecutorServiceForPeriodicConfigurationCapture(configWritePeriod, configWritePeriodInitialDelay);
-        return 0;
+        return SUCCESS;
     }
 
     private static void inform(String message) {
@@ -408,11 +413,11 @@ private static <T> T error(T result, String message) {
         return result;
     }
 
-    private static <T> T usage(T result, String message) {
+    private static int usage(String message) {
         inform(message);
         inform("Example usage: -agentlib:native-image-agent=config-output-dir=/path/to/config-dir/");
         inform("For details, please read AutomaticMetadataCollection.md or https://www.graalvm.org/dev/reference-manual/native-image/metadata/AutomaticMetadataCollection/");
-        return result;
+        return USAGE_ERROR;
     }
 
     private static AccessAdvisor createAccessAdvisor(boolean builtinHeuristicFilter, ConfigurationFilter callerFilter, ConfigurationFilter accessFilter) {
@@ -689,7 +694,14 @@ protected int onUnloadCallback(JNIJavaVM vm) {
          * The epilogue of this method does not tear down our VM: we don't seem to observe all
          * threads that end and therefore can't detach them, so we would wait forever for them.
          */
-        return 0;
+        return SUCCESS;
+    }
+
+    static class ExitCodes {
+        static final int SUCCESS = 0;
+        static final int USAGE_ERROR = 1;
+        static final int PARSE_ERROR = 2;
+        static final int AGENT_ERROR = 3;
     }
 
     @SuppressWarnings("unused")