8374444: Fix simple -Wzero-as-null-pointer-constant warnings

Reviewed-by: aboldtch

Author: Kim Barrett

src/hotspot/share/cds/aotMappedHeapWriter.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2026, 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
@@ -124,7 +124,7 @@ CompressedOops::Mode AOTMappedHeapWriter::narrow_oop_mode() {
 
 address AOTMappedHeapWriter::narrow_oop_base() {
   if (is_writing_deterministic_heap()) {
-    return (address)0;
+    return nullptr;
   } else {
     return CompressedOops::base();
   }

src/hotspot/share/jvmci/jvmciCompilerToVM.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2026, 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
@@ -1218,7 +1218,7 @@ C2V_VMENTRY_0(jint, installCode0, (JNIEnv *env, jobject,
   return result;
 C2V_END
 
-C2V_VMENTRY_0(jobject, getInvalidationReasonDescription, (JNIEnv *env, jobject, jint invalidation_reason))
+C2V_VMENTRY_NULL(jobject, getInvalidationReasonDescription, (JNIEnv *env, jobject, jint invalidation_reason))
   HandleMark hm(THREAD);
   JNIHandleMark jni_hm(thread);
   nmethod::InvalidationReason reason = static_cast<nmethod::InvalidationReason>(invalidation_reason);

src/hotspot/share/opto/vectorization.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2026, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2023, Arm Limited. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -132,10 +132,10 @@ VStatus VLoop::check_preconditions_helper() {
       tty->print_cr(" Infrastructure for speculative runtime-checks:");
       if (_auto_vectorization_parse_predicate_proj != nullptr) {
         tty->print_cr("  auto_vectorization_parse_predicate_proj: speculate and trap");
-        _auto_vectorization_parse_predicate_proj->dump_bfs(5,0,"");
+        _auto_vectorization_parse_predicate_proj->dump_bfs(5, nullptr, "");
       } else if (_multiversioning_fast_proj != nullptr) {
         tty->print_cr("  multiversioning_fast_proj: speculate and multiversion");
-        _multiversioning_fast_proj->dump_bfs(5,0,"");
+        _multiversioning_fast_proj->dump_bfs(5, nullptr, "");
       } else {
         tty->print_cr("  Not found.");
       }

src/hotspot/share/runtime/continuationFreezeThaw.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2026, 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
@@ -1736,8 +1736,8 @@ static void verify_frame_kind(frame& top, Continuation::preempt_kind preempt_kin
       m = top.interpreter_frame_method();
       assert(!m->is_native() || m->is_synchronized(), "invalid method %s", m->external_name());
       address bcp = top.interpreter_frame_bcp();
-      assert(bcp != 0 || m->is_native(), "");
-      at_sync_method = m->is_synchronized() && (bcp == 0 || bcp == m->code_base());
+      assert(bcp != nullptr || m->is_native(), "");
+      at_sync_method = m->is_synchronized() && (bcp == nullptr || bcp == m->code_base());
       // bcp is advanced on monitorenter before making the VM call, adjust for that.
       bool at_sync_bytecode = bcp > m->code_base() && Bytecode(m, bcp - 1).code() == Bytecodes::Code::_monitorenter;
       assert(at_sync_method || at_sync_bytecode, "");

test/hotspot/gtest/nmt/test_regions_tree.cpp

@@ -48,7 +48,7 @@ TEST_VM_F(NMTRegionsTreeTest, ReserveCommitTwice) {
   }
   {
     VMATree::SummaryDiff diff, not_used;
-    rt.commit_region(0, 50, ncs, not_used);
+    rt.commit_region(nullptr, 50, ncs, not_used);
     rt.reserve_mapping(0, 100, rd, diff);
     EXPECT_EQ(0, diff.tag[NMTUtil::tag_to_index(mtTest)].reserve);
     EXPECT_EQ(-50, diff.tag[NMTUtil::tag_to_index(mtTest)].commit);
@@ -62,10 +62,10 @@ TEST_VM_F(NMTRegionsTreeTest, ReserveCommitTwice) {
 
   {
     VMATree::SummaryDiff diff1, diff2;
-    rt.commit_region(0, 50, ncs, diff1);
+    rt.commit_region(nullptr, 50, ncs, diff1);
     EXPECT_EQ(0, diff1.tag[NMTUtil::tag_to_index(mtGC)].reserve);
     EXPECT_EQ(50, diff1.tag[NMTUtil::tag_to_index(mtGC)].commit);
-    rt.commit_region(0, 50, ncs, diff2);
+    rt.commit_region(nullptr, 50, ncs, diff2);
     EXPECT_EQ(0, diff2.tag[NMTUtil::tag_to_index(mtTest)].reserve);
     EXPECT_EQ(0, diff2.tag[NMTUtil::tag_to_index(mtTest)].commit);
   }
@@ -78,7 +78,7 @@ TEST_VM_F(NMTRegionsTreeTest, CommitUncommitRegion) {
   rt.reserve_mapping(0, 100, rd, not_used);
   {
     VMATree::SummaryDiff diff;
-    rt.commit_region(0, 50, ncs, diff);
+    rt.commit_region(nullptr, 50, ncs, diff);
     EXPECT_EQ(0, diff.tag[NMTUtil::tag_to_index(mtTest)].reserve);
     EXPECT_EQ(50, diff.tag[NMTUtil::tag_to_index(mtTest)].commit);
   }
@@ -90,7 +90,7 @@ TEST_VM_F(NMTRegionsTreeTest, CommitUncommitRegion) {
   }
   {
     VMATree::SummaryDiff diff;
-    rt.uncommit_region(0, 50, diff);
+    rt.uncommit_region(nullptr, 50, diff);
     EXPECT_EQ(0, diff.tag[NMTUtil::tag_to_index(mtTest)].reserve);
     EXPECT_EQ(-50, diff.tag[NMTUtil::tag_to_index(mtTest)].commit);
   }
@@ -153,4 +153,4 @@ TEST_VM_F(NMTRegionsTreeTest, VisitCommittedRegions) {
     return true;
   });
   EXPECT_EQ(count, 4UL);
-}
+}