8335688: Fix -Wzero-as-null-pointer-constant warnings from fflush calls in jvmti tests

Reviewed-by: jwaters, coleenp

Author: Kim Barrett

test/hotspot/jtreg/serviceability/jvmti/AddModuleUsesAndProvides/libAddModuleUsesAndProvidesTest.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2024, 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
@@ -200,7 +200,7 @@ Java_MyPackage_AddModuleUsesAndProvidesTest_checkUses(JNIEnv *env,
         throw_exc(env, "Check #UC3: service can not be used unexpectedly");
         return FAILED;
     }
-    fflush(0);
+    fflush(NULL);
     return PASSED;
 }
 
@@ -275,7 +275,7 @@ Java_MyPackage_AddModuleUsesAndProvidesTest_checkProvides(JNIEnv *env,
         throw_exc(env, "Check #PC2: error in add provides to baseModule with correct service and serviceImpl");
         return FAILED;
     }
-    fflush(0);
+    fflush(NULL);
     return PASSED;
 }
 

test/hotspot/jtreg/serviceability/jvmti/GenerateEvents/libGenerateEvents1.cpp

@@ -71,7 +71,7 @@ CompiledMethodLoad(jvmtiEnv* jvmti, jmethodID method,
   check_jvmti_status(env, err, "CompiledMethodLoad: Error in JVMTI GetMethodName");
 
   printf("%s: CompiledMethodLoad: %s%s\n", AGENT_NAME, name, sign);
-  fflush(0);
+  fflush(nullptr);
 }
 
 JNIEXPORT jint JNICALL

test/hotspot/jtreg/serviceability/jvmti/GenerateEvents/libGenerateEvents2.cpp

@@ -71,7 +71,7 @@ CompiledMethodLoad(jvmtiEnv* jvmti, jmethodID method,
   check_jvmti_status(env, err, "CompiledMethodLoad: Error in JVMTI GetMethodName");
 
   printf("%s: CompiledMethodLoad: %s%s\n", AGENT_NAME, name, sign);
-  fflush(0);
+  fflush(nullptr);
 }
 
 JNIEXPORT jint JNICALL
@@ -132,7 +132,7 @@ Java_MyPackage_GenerateEventsTest_agent2FailStatus(JNIEnv *env, jclass cls) {
     printf("check2: Unexpected non-zero event count in agent2: %d\n", agent2_event_count);
   }
   printf("\n");
-  fflush(0);
+  fflush(nullptr);
 
   return fail_status;
 }

test/hotspot/jtreg/serviceability/jvmti/GetClassFields/FilteredFields/libFilteredFieldsTest.cpp

@@ -35,7 +35,7 @@ jint Agent_Initialize(JavaVM *jvm, char *options, void *reserved) {
     jint res = jvm->GetEnv((void **)&jvmti, JVMTI_VERSION_1_1);
     if (res != JNI_OK || jvmti == nullptr) {
         printf("Wrong result of a valid call to GetEnv!\n");
-        fflush(0);
+        fflush(nullptr);
         return JNI_ERR;
     }
     return JNI_OK;
@@ -72,7 +72,7 @@ Java_FilteredFieldsTest_getJVMTIFieldCount(JNIEnv *env, jclass cls, jclass clazz
         printf("  [%d]: %s\n", i, name);
         jvmti->Deallocate((unsigned char *)name);
     }
-    fflush(0);
+    fflush(nullptr);
     return fcount;
 }
 

test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/MissedStackMapFrames/libMissedStackMapFrames.cpp

@@ -31,7 +31,7 @@ static void _log(const char* format, ...) {
   va_start(args, format);
   vprintf(format, args);
   va_end(args);
-  fflush(0);
+  fflush(nullptr);
 }
 
 static jvmtiEnv* jvmti = nullptr;

test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/RedefineRetransform/libRedefineRetransform.cpp

@@ -36,7 +36,7 @@ static void _log(const char* format, ...) {
     va_start(args, format);
     vprintf(format, args);
     va_end(args);
-    fflush(0);
+    fflush(nullptr);
 }
 
 static bool isTestClass(const char* name) {

test/hotspot/jtreg/serviceability/jvmti/events/FramePop/framepop02/libframepop02.cpp

@@ -194,7 +194,7 @@ void JNICALL MethodEntry(jvmtiEnv *jvmti, JNIEnv *jni,
   {
     if (printdump == JNI_TRUE) {
       print_current_time();
-      fflush(0);
+      fflush(nullptr);
       LOG(">>> %sMethod entry\n>>>", (isNative == JNI_TRUE) ? "Native " : "");
       printInfo(jni, jvmti, thr, method, frameCount);
     }
@@ -231,7 +231,7 @@ void JNICALL FramePop(jvmtiEnv *jvmti, JNIEnv *jni,
   {
     if (printdump == JNI_TRUE) {
       print_current_time();
-      fflush(0);
+      fflush(nullptr);
       LOG(" >>> Frame Pop\n>>>");
       printInfo(jni, jvmti, thr, method, frameCount);
     }

test/hotspot/jtreg/serviceability/jvmti/thread/GetStackTrace/get_stack_trace.hpp

@@ -70,7 +70,7 @@ int compare_stack_trace(jvmtiEnv *jvmti, JNIEnv *jni, jthread thread,
 
     int exp_idx = expected_frames_length - 1 - i;
     printf("expected idx %d\n", exp_idx);
-    fflush(0);
+    fflush(nullptr);
     if (i < expected_frames_length) {
 
       // for generated classes don't compare lambda indicies

test/hotspot/jtreg/serviceability/jvmti/vthread/SuspendResume1/libSuspendResume1.cpp

@@ -138,7 +138,7 @@ check_suspended_state(JNIEnv* jni, jthread thread, int thr_idx, char* tname, con
 
       LOG("## Agent: %s:  virtual thread of carrier thread has state: %s (%d)\n",
           func_name, TranslateState(state), (int)state);
-      fflush(0);
+      fflush(nullptr);
     }
     set_agent_fail_status();
     fatal(jni, "check_resumed_state: expected SUSPENDED flag in thread state");
@@ -169,7 +169,7 @@ check_resumed_state(JNIEnv* jni, jthread thread, int thr_idx, char* tname, const
 
       LOG("## Agent: %s:  virtual thread of carrier thread has state: %s (%d)\n",
           func_name, TranslateState(state), (int)state);
-      fflush(0);
+      fflush(nullptr);
     }
     set_agent_fail_status();
     fatal(jni, "check_resumed_state: NOT expected SUSPENDED flag in thread state");
@@ -210,7 +210,7 @@ test_thread_resume(JNIEnv* jni, jthread thread, int thr_idx, char* tname) {
 
     LOG("## Agent: test_thread_resume:  virtual thread of carrier thread has state: %s (%d)\n",
         TranslateState(state), (int)state);
-    fflush(0);
+    fflush(nullptr);
   }
   check_jvmti_status(jni, err, "test_thread_resume: error in JVMTI ResumeThread");
 

test/hotspot/jtreg/vmTestbase/nsk/jvmti/GetClassFields/getclfld007/getclfld007.cpp

@@ -86,7 +86,7 @@ Java_nsk_jvmti_GetClassFields_getclfld007_check(JNIEnv *env, jclass cls, jclass
 
     if (jvmti == nullptr) {
         printf("JVMTI client was not properly loaded!\n");
-        fflush(0);
+        fflush(nullptr);
         result = STATUS_FAILED;
         return;
     }
@@ -98,7 +98,7 @@ Java_nsk_jvmti_GetClassFields_getclfld007_check(JNIEnv *env, jclass cls, jclass
     if (err != JVMTI_ERROR_NONE) {
         printf("GetClassFields unexpected error: %s (%d)\n",
                TranslateError(err), err);
-        fflush(0);
+        fflush(nullptr);
         result = STATUS_FAILED;
         return;
     }
@@ -132,7 +132,7 @@ Java_nsk_jvmti_GetClassFields_getclfld007_check(JNIEnv *env, jclass cls, jclass
         jvmti->Deallocate((unsigned char *)name);
         jvmti->Deallocate((unsigned char *)sig);
     }
-    fflush(0);
+    fflush(nullptr);
 }
 
 JNIEXPORT int JNICALL