8309044: Replace NULL with nullptr, final sweep of hotspot code #14198

jdksjolen · 2023-05-29T10:09:15Z

A final sweep of Hotspot to remove all re-added NULLs. With only 110 changes I'd appreciate if this was considered trivial.

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8309044: Replace NULL with nullptr, final sweep of hotspot code

Reviewers

Stefan Karlsson (@stefank - Reviewer) ⚠️ Review applies to c7e28571
David Holmes (@dholmes-ora - Reviewer) ⚠️ Review applies to c7e28571
Vladimir Kozlov (@vnkozlov - Reviewer)
Amit Kumar (@offamitkumar - Author)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/14198/head:pull/14198
$ git checkout pull/14198

Update a local copy of the PR:
$ git checkout pull/14198
$ git pull https://git.openjdk.org/jdk.git pull/14198/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 14198

View PR using the GUI difftool:
$ git pr show -t 14198

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/14198.diff

Webrev

Link to Webrev Comment

bridgekeeper · 2023-05-29T10:10:44Z

👋 Welcome back jsjolen! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2023-05-29T10:12:04Z

@jdksjolen The following labels will be automatically applied to this pull request:

graal
hotspot
serviceability
shenandoah

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

jdksjolen

All of the stuff to actually keep.

jdksjolen · 2023-05-29T10:09:45Z

src/hotspot/cpu/aarch64/jvmciCodeInstaller_aarch64.cpp


 void CodeInstaller::pd_relocate_JavaMethod(CodeBuffer &cbuf, methodHandle& method, jint pc_offset, JVMCI_TRAPS) {
-  NativeCall* call = NULL;
+  NativeCall* call = nullptr;


jdksjolen · 2023-05-29T10:09:52Z

src/hotspot/cpu/aarch64/jvmciCodeInstaller_aarch64.cpp

    // Check for proper post_call_nop
    NativePostCallNop* nop = nativePostCallNop_at(call->next_instruction_address());
-    if (nop == NULL) {
+    if (nop == nullptr) {


jdksjolen · 2023-05-29T10:10:24Z

src/hotspot/cpu/ppc/templateTable_ppc_64.cpp

  __ ld_ptr(method, array_base_offset + in_bytes(ResolvedIndyEntry::method_offset()), cache);

-  // The invokedynamic is unresolved iff method is NULL
+  // The invokedynamic is unresolved iff method is null


jdksjolen · 2023-05-29T10:10:31Z

src/hotspot/cpu/riscv/gc/shared/barrierSetAssembler_riscv.cpp

  // Make sure klass is 'reasonable', which is not zero.
  __ load_klass(obj, obj, tmp1); // get klass
-  __ beqz(obj, error);           // if klass is NULL it is broken
+  __ beqz(obj, error);           // if klass is null it is broken


jdksjolen · 2023-05-29T10:10:39Z

src/hotspot/cpu/riscv/stubGenerator_riscv.cpp

    StubRoutines::_forward_exception_entry = generate_forward_exception();

-    if (UnsafeCopyMemory::_table == NULL) {
+    if (UnsafeCopyMemory::_table == nullptr) {


jdksjolen · 2023-05-29T10:20:52Z

src/hotspot/share/utilities/ostream.cpp

    start_log();
  } else {
-    // and leave xtty as nullptr
+    // and leave xtty as null


jdksjolen · 2023-05-29T10:20:56Z

src/hotspot/share/utilities/ostream.cpp

+        assert(p->key() != nullptr, "p->key() is null");
        if (p->readable()) {
          // Print in two stages to avoid problems with long
          // keys/values.
          text->print_raw(p->key());
          text->put('=');
-          assert(p->value() != nullptr, "p->value() is nullptr");
+          assert(p->value() != nullptr, "p->value() is null");


jdksjolen · 2023-05-29T10:21:01Z

src/hotspot/share/utilities/unsigned5.hpp

    Writer(const ARR& array)
      : _array(const_cast<ARR&>(array)), _limit_ptr(nullptr), _position(0) {
-      // Note: if _limit_ptr is nullptr, the ARR& is never reassigned,
+      // Note: if _limit_ptr is null, the ARR& is never reassigned,


jdksjolen · 2023-05-29T10:21:05Z

src/hotspot/share/utilities/utf8.hpp

  // Utility methods

-  // Returns nullptr if 'c' it not found. This only works as long
+  // Returns null if 'c' it not found. This only works as long


jdksjolen · 2023-05-29T10:21:14Z

src/hotspot/share/utilities/vmError.hpp

  static char        _detail_msg[1024];

-  static Thread*     _thread;           // nullptr if it's native thread
+  static Thread*     _thread;           // null if it's native thread


mlbridge · 2023-05-29T11:02:26Z

Webrevs

01: Full - Incremental (c9d9c30c)
00: Full (c7e28571)

offamitkumar · 2023-05-29T12:23:43Z

not a review, but would you like to check if these could replaced as well :-)

./cpu/ppc/macroAssembler_ppc.hpp:735:  void load_klass_check_null(Register dst, Register src, Label* is_null = NULL);
./cpu/ppc/stubGenerator_ppc.cpp:4700:    if (UnsafeCopyMemory::_table == NULL) {
./cpu/riscv/codeBuffer_riscv.cpp:74:  if (cb->stubs()->maybe_expand_to_ensure_remaining(total_requested_size) && cb->blob() == NULL) {
./share/include/jvm.h:423: * Find a class from a boot class loader. Returns NULL if class not found.
./share/include/cds.h:72:  char*   _mapped_base;       // Actually mapped address (NULL if this region is not mapped).
./share/opto/runtime.cpp:491:  fields[TypeFunc::Parms+0] = NULL; // void

stefank

Looks good. Though, I'd prefer if we could slightly tweak the following two print lines.

stefank · 2023-05-29T15:36:31Z

src/hotspot/share/gc/z/zHeap.cpp

  st->print(PTR_FORMAT " is a zaddress: ", untype(addr));

  if (addr == zaddress::null) {
-    st->print_raw_cr("NULL");


I'd prefer if this were left as either NULL or null.

stefank · 2023-05-29T15:36:36Z

src/hotspot/share/gc/z/zHeap.cpp


  if (addr == zaddress::null) {
-    st->print_raw_cr("NULL");
+    st->print_raw_cr("nullptr");


I'd prefer if this were left as either NULL or null.

Suggest: null

openjdk · 2023-05-29T15:43:04Z

@jdksjolen This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8309044: Replace NULL with nullptr, final sweep of hotspot code

Reviewed-by: stefank, dholmes, kvn, amitkumar

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 29 new commits pushed to the master branch:

927a9ed: 8240774: [REDO] G1DirtyCardQueue destructor has useless flush
119994f: 8308997: RISC-V: Sign extend when comparing 32-bit value with zero instead of testing the sign bit
327733c: 8308986: Disable svc tests failing with virtual thread factory
1e6770f: 8308341: JNI_GetCreatedJavaVMs returns a partially initialized JVM
cb40db0: 8309134: Augment test/langtools/tools/javac/versions/Versions.java for JDK 21 language changes
de7fd1c: 8307944: ClassFileDumper should only load java.nio.file.Path if enabled
7891de3: 8297885: misc sun/security/pkcs11 tests timed out
323d6ce: 8308960: Decouple internal Version and OperatingSystem classes
1b8e6bf: 8308987: Update java.lang.Class to use javadoc snippets
04b0e78: 8307648: java/net/httpclient/ExpectContinueTest.java timed out
... and 19 more: https://git.openjdk.org/jdk/compare/70130d3b16e76364ede72dec421ed6e7c40467fe...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

dholmes-ora

Looks good. A few suggested changes below.

Can we now poison NULL so it can't get reintroduced? Or would that potentially break standard headers?

Thanks

dholmes-ora · 2023-05-30T00:47:58Z

src/hotspot/cpu/ppc/templateTable_ppc_64.cpp

  __ ld_ptr(method, array_base_offset + in_bytes(ResolvedIndyEntry::method_offset()), cache);

-  // The invokedynamic is unresolved iff method is NULL
+  // The invokedynamic is unresolved iff method is nullptr


Suggest: null

dholmes-ora · 2023-05-30T00:48:32Z

src/hotspot/cpu/x86/gc/shared/barrierSetAssembler_x86.cpp

  __ load_klass(obj, obj, tmp1);  // get klass
  __ testptr(obj, obj);
-  __ jcc(Assembler::zero, error); // if klass is NULL it is broken
+  __ jcc(Assembler::zero, error); // if klass is nullptr it is broken


suggest: null

dholmes-ora · 2023-05-30T00:49:47Z

src/hotspot/share/gc/z/zHeap.cpp


  if (addr == zaddress::null) {
-    st->print_raw_cr("NULL");
+    st->print_raw_cr("nullptr");


Suggest: null

dholmes-ora · 2023-05-30T00:50:04Z

src/hotspot/share/gc/z/zHeap.cpp


  if (addr == zaddress::null) {
-    st->print_raw_cr("NULL");
+    st->print_raw_cr("nullptr");


Suggest: null

dholmes-ora · 2023-05-30T00:52:18Z

src/hotspot/share/runtime/globals.hpp

                                                                            \
  develop(bool, InterceptOSException, false,                                \
-          "Start debugger when an implicit OS (e.g. nullptr) "                 \
+          "Start debugger when an implicit OS (e.g. null) "                 \


Suggest: null pointer

jdksjolen · 2023-05-30T19:09:23Z

Hi, thank you all for the suggestions! I've now applied them. I'll look at integrating tomorrow.

vnkozlov

Good.

offamitkumar

Thanks for addressing the comment. Looks Good :-)

jdksjolen · 2023-05-31T09:18:15Z

Right, seems like the Windows CI fails at fetching JTReg. I'm merging this, thank you all for the reviews.

/integrate

openjdk · 2023-05-31T09:19:56Z

Going to push as commit 4f16161.
Since your change was applied there have been 30 commits pushed to the master branch:

8823626: 8309048: Remove malloc locker test case
927a9ed: 8240774: [REDO] G1DirtyCardQueue destructor has useless flush
119994f: 8308997: RISC-V: Sign extend when comparing 32-bit value with zero instead of testing the sign bit
327733c: 8308986: Disable svc tests failing with virtual thread factory
1e6770f: 8308341: JNI_GetCreatedJavaVMs returns a partially initialized JVM
cb40db0: 8309134: Augment test/langtools/tools/javac/versions/Versions.java for JDK 21 language changes
de7fd1c: 8307944: ClassFileDumper should only load java.nio.file.Path if enabled
7891de3: 8297885: misc sun/security/pkcs11 tests timed out
323d6ce: 8308960: Decouple internal Version and OperatingSystem classes
1b8e6bf: 8308987: Update java.lang.Class to use javadoc snippets
... and 20 more: https://git.openjdk.org/jdk/compare/70130d3b16e76364ede72dec421ed6e7c40467fe...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-05-31T09:20:12Z

@jdksjolen Pushed as commit 4f16161.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

TobiHartmann · 2023-06-01T05:23:25Z

What's the plan now to prevent re-introducing NULL?

theRealAph · 2023-06-01T09:43:30Z

Can we now poison NULL so it can't get reintroduced? Or would that potentially break standard headers?

I'm sure it would. Maybe some changes to Skara?

jdksjolen · 2023-06-01T09:50:58Z

What's the plan now to prevent re-introducing NULL?

Hi Tobias. The only plan in place is social, the reviewers have to look out for it. I am however researching how to do this through machine. I'm currently researching ways of preventing any re-introductions by machine. These include poisoning the NULL macro by re-defining it and finding a tool which is capable of parsing C++ code which is yet to go through the pre-processor.

dougxc · 2023-06-01T10:13:18Z

It may be simpler to use simple grepping + an allow list. For example using ag and grep seems to catch the few remaining offenders:

> ag NULL src/hotspot/ --cpp | grep -v _NULL | grep -v NULL_ | grep -v -E '[A-Z]NULL' | grep -v -E '//.*NULL' | grep -v '"NULL"'
src/hotspot/cpu/ppc/macroAssembler_ppc.hpp:735:  void load_klass_check_null(Register dst, Register src, Label* is_null = NULL);
src/hotspot/cpu/ppc/stubGenerator_ppc.cpp:4700:    if (UnsafeCopyMemory::_table == NULL) {
src/hotspot/cpu/x86/jvmciCodeInstaller_x86.cpp:191:    if (nop == NULL) {
src/hotspot/cpu/riscv/codeBuffer_riscv.cpp:74:  if (cb->stubs()->maybe_expand_to_ensure_remaining(total_requested_size) && cb->blob() == NULL) {
src/hotspot/cpu/riscv/stubGenerator_riscv.cpp:4019:    if (UnsafeCopyMemory::_table == NULL) {
src/hotspot/cpu/riscv/stubGenerator_riscv.cpp:4077:    if (bs_nm != NULL) {
src/hotspot/cpu/aarch64/jvmciCodeInstaller_aarch64.cpp:125:  NativeCall* call = NULL;
src/hotspot/cpu/aarch64/jvmciCodeInstaller_aarch64.cpp:158:    if (nop == NULL) {
src/hotspot/share/jfr/dcmd/jfrDcmds.hpp:162:    JavaPermission p = {"java.lang.management.ManagementPermission", "monitor", NULL};
src/hotspot/share/jfr/dcmd/jfrDcmds.hpp:187:    JavaPermission p = {"java.lang.management.ManagementPermission", "monitor", NULL};
src/hotspot/share/include/jvm.h:423: * Find a class from a boot class loader. Returns NULL if class not found.
src/hotspot/share/prims/jvmtiAgent.cpp:375:  const jint err = (*on_load_entry)(&main_vm, const_cast<char*>(agent->options()), NULL);
src/hotspot/share/prims/whitebox.cpp:1885:  if (cp->cache() == NULL) {
src/hotspot/share/prims/whitebox.cpp:1894:  if (cp->cache() == NULL) {
src/hotspot/share/classfile/stringTable.hpp:150:  static oop init_shared_table(const DumpedInternedStrings* dumped_interned_strings) NOT_CDS_JAVA_HEAP_RETURN_(NULL);
src/hotspot/share/utilities/globalDefinitions_xlc.hpp:95:  #undef NULL
src/hotspot/share/utilities/globalDefinitions_xlc.hpp:96:  #define NULL 0L
src/hotspot/share/utilities/globalDefinitions_xlc.hpp:98:  #ifndef NULL
src/hotspot/share/utilities/globalDefinitions_xlc.hpp:99:    #define NULL 0
src/hotspot/share/cds/filemap.cpp:363:  assert(ent != NULL, "sanity");
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:65:#undef NULL
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:69:#define NULL 0LL
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:71:#ifndef NULL
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:72:#define NULL 0
src/hotspot/share/utilities/globalDefinitions.cpp:162:  static_assert(sizeof(NULL) == sizeof(char*), "NULL must be same size as pointer");
src/hotspot/share/adlc/output_c.cpp:279:  for (pipeline->_reslist.reset(); (resource = pipeline->_reslist.iter()) != NULL;) {
src/hotspot/share/adlc/output_c.cpp:305:  for (pipeline->_reslist.reset(); (resource = pipeline->_reslist.iter()) != NULL;) {
src/hotspot/share/adlc/output_c.cpp:368:  for (pipeline->_reslist.reset(); (resource = pipeline->_reslist.iter()) != NULL;) {
src/hotspot/share/adlc/output_c.cpp:393:  for (pipeline->_reslist.reset(); (resource = pipeline->_reslist.iter()) != NULL;) {
src/hotspot/share/adlc/output_c.cpp:1009:  for (_pipeline->_reslist.reset(); (resource = _pipeline->_reslist.iter()) != NULL;) {
src/hotspot/share/gc/x/xBarrierSet.inline.hpp:187:    return Raw::oop_arraycopy_in_heap(nullptr, 0, src, NULL, 0, dst, length);
src/hotspot/share/gc/x/xPageTable.inline.hpp:43:    if (entry != NULL && entry != _prev) {
src/hotspot/share/gc/x/xBarrier.cpp:242:  return NULL;
src/hotspot/share/oops/cpCache.cpp:888:  LogStream* log_stream = NULL;
src/hotspot/share/oops/cpCache.cpp:906:    assert(resolved_references->obj_at(appendix_index) == NULL, "init just once");
src/hotspot/share/oops/cpCache.cpp:914:  if (log_stream != NULL) {
src/hotspot/share/opto/runtime.cpp:491:  fields[TypeFunc::Parms+0] = NULL; // void
src/hotspot/share/jvmci/jvmciEnv.cpp:366:    if (ex != NULL) {

TobiHartmann · 2023-06-02T05:20:20Z

I think if we just rely on reviews, NULLs will slip through again and we would need to have regular cleanup PRs.

Doug's idea seems simple enough to implement in Skara/jcheck. An alternative to whitelisting would be a warning in the offending PR or a requirement for "special approvement" of such changes (for example, via a Skara command).

TheShermanTanker · 2024-01-21T12:16:11Z

I'm an entire year late, but if poisoning NULL is desired, what about #pragma GCC poison?

TheShermanTanker · 2024-01-21T12:19:02Z

For Visual C++, that would be #pragma deprecated("NULL")

To quote Microsoft:
"You can deprecate macro names. Place the macro name in quotes or else macro expansion will occur."

I have no idea how to achieve this with the xlc compiler

kimbarrett · 2024-01-22T08:59:30Z

I don't think #pragma GCC poison works for us. It would complain about a
system or library header that uses NULL and is included after the pragma.

MSVC's deprecation pragma might work for this, at least for shared and
Windows-specific code. I couldn't find a way to use it for FORBID_C_FUNCTION,
but the problems I encountered for that don't seem applicable in this case.

However, there are still a lot of NULL's left. All of the per-cpu .ad files,
and the jvmtiXXX.xsl files contain NULL's that will appear in the associated
generated code. Also, NULL usage in gtests doesn't seem to have been addressed
yet.

But it does look like there's been a bit of backsliding:
https://bugs.openjdk.org/browse/JDK-8324286

TheShermanTanker · 2024-01-22T09:26:04Z

I don't think #pragma GCC poison works for us. It would complain about a
system or library header that uses NULL and is included after the pragma.

I see, that's a shame in that case

However, there are still a lot of NULL's left. All of the per-cpu .ad files, and the jvmtiXXX.xsl files contain NULL's that will appear in the associated generated code. Also, NULL usage in gtests doesn't seem to have been addressed yet.

But it does look like there's been a bit of backsliding: https://bugs.openjdk.org/browse/JDK-8324286

That's a little worrying, maybe the Style Guide's NULL section could be reworded since now most usages of NULL are nullptr? The .ad files and .xsl files are a bit of a problem though

MSVC's deprecation pragma might work for this, at least for shared and
Windows-specific code. I couldn't find a way to use it for FORBID_C_FUNCTION,
but the problems I encountered for that don't seem applicable in this case.

The deprecation pragma only works for macros and identifiers, it doesn't accept method signatures and would warn for every time a identifier is used, even in the method's declaration itself! Probably can't be used in FORBID_C_FUNCTION as mentioned above, but sounds good for a macro like NULL

I've also been trying to implement FORBID_C_FUNCTION and ALLOW_C_FUNCTION portably, speaking of it, but it hasn't been going great so far :/ #17387

openjdk bot added graal graal-dev@openjdk.org serviceability serviceability-dev@openjdk.org hotspot hotspot-dev@openjdk.org shenandoah shenandoah-dev@openjdk.org labels May 29, 2023

jdksjolen commented May 29, 2023

View reviewed changes

Fix remaining work

c7e2857

jdksjolen force-pushed the JDK-8309044 branch from ee9045f to c7e2857 Compare May 29, 2023 10:55

jdksjolen marked this pull request as ready for review May 29, 2023 10:55

openjdk bot added the rfr Pull request is ready for review label May 29, 2023

stefank approved these changes May 29, 2023

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label May 29, 2023

dholmes-ora approved these changes May 30, 2023

View reviewed changes

jdksjolen added 2 commits May 30, 2023 21:08

Suggestions

b19b38d

Align

c9d9c30

vnkozlov approved these changes May 30, 2023

View reviewed changes

offamitkumar approved these changes May 31, 2023

View reviewed changes

openjdk bot added the integrated Pull request has been integrated label May 31, 2023

openjdk bot closed this May 31, 2023

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels May 31, 2023

This comment was marked as resolved.

Sign in to view

8309044: Replace NULL with nullptr, final sweep of hotspot code #14198

8309044: Replace NULL with nullptr, final sweep of hotspot code #14198

Uh oh!

Conversation

jdksjolen commented May 29, 2023 • edited by openjdk bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Progress

Issue

Reviewers

Reviewing

Webrev

Uh oh!

bridgekeeper bot commented May 29, 2023

Uh oh!

openjdk bot commented May 29, 2023

Uh oh!

jdksjolen left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

mlbridge bot commented May 29, 2023 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Webrevs

Uh oh!

offamitkumar commented May 29, 2023

Uh oh!

stefank left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

openjdk bot commented May 29, 2023 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

dholmes-ora left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

jdksjolen commented May 30, 2023

Uh oh!

vnkozlov left a comment

Choose a reason for hiding this comment

Uh oh!

offamitkumar left a comment

Choose a reason for hiding this comment

Uh oh!

jdksjolen commented May 31, 2023

Uh oh!

jdksjolen commented May 29, 2023 •

edited by openjdk bot

Loading

mlbridge bot commented May 29, 2023 •

edited

Loading

openjdk bot commented May 29, 2023 •

edited

Loading