JDK-8301070: Replace NULL with nullptr in share/memory/ #12185

jdksjolen · 2023-01-25T11:45:47Z

Hi, this PR changes all occurrences of NULL to nullptr for the subdirectory share/memory/. Unfortunately the script that does the change isn't perfect, and so we
need to comb through these manually to make sure nothing has gone wrong. I also review these changes but things slip past my eyes sometimes.

Here are some typical things to look out for:

No changes but copyright header changed (probably because I reverted some changes but forgot the copyright).
Macros having their NULL changed to nullptr, these are added to the script when I find them. They should be NULL.
nullptr in comments and logs. We try to use lower case "null" in these cases as it reads better. An exception is made when code expressions are in a comment.

An example of this:

// This function returns null
void* ret_null();
// This function returns true if *x == nullptr
bool is_nullptr(void** x);

Note how nullptr participates in a code expression here, we really are talking about the specific value nullptr.

Thanks!

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-8301070: Replace NULL with nullptr in share/memory/

Reviewers

Stefan Karlsson (@stefank - Reviewer) ⚠️ Review applies to def9b5f3
Thomas Stuefe (@tstuefe - Reviewer) ⚠️ Review applies to def9b5f3

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/12185/head:pull/12185
$ git checkout pull/12185

Update a local copy of the PR:
$ git checkout pull/12185
$ git pull https://git.openjdk.org/jdk pull/12185/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 12185

View PR using the GUI difftool:
$ git pr show -t 12185

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/12185.diff

bridgekeeper · 2023-01-25T11:48:24Z

👋 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 · 2023-01-25T11:51:41Z

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

hotspot
serviceability

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

Found one manual fix

jdksjolen · 2023-01-25T15:03:38Z

src/hotspot/share/memory/heap.cpp

  insert_after(prev, b);
  _last_insert_point = prev;
 }

 /**
 * Search freelist for an entry on the list with the best fit.
- * @return NULL, if no one was found
+ * @return nullptr, if no one was found


mlbridge · 2023-01-25T15:17:55Z

Webrevs

01: Full - Incremental (1b09b9a7)
00: Full (def9b5f3)

jdksjolen · 2023-01-25T16:16:52Z

Passes tier1.

stefank · 2023-01-26T09:16:49Z

src/hotspot/share/memory/guardedMemory.hpp

@@ -226,7 +226,7 @@ class GuardedMemory : StackObj { // Wrapper on stack
  /**
   * Return the general purpose tag.
   *
-   * @return the general purpose tag, defaults to NULL.
+   * @return the general purpose tag, defaults to nullptr.


nullptr => null?

stefank · 2023-01-26T09:17:09Z

src/hotspot/share/memory/guardedMemory.hpp

-  void* wrap_with_guards(void* base_ptr, size_t user_size, const void* tag = NULL) {
-    assert(base_ptr != NULL, "Attempt to wrap NULL with memory guard");
+  void* wrap_with_guards(void* base_ptr, size_t user_size, const void* tag = nullptr) {
+    assert(base_ptr != nullptr, "Attempt to wrap nullptr with memory guard");


wrap nullptr => wrap null?

stefank · 2023-01-26T09:17:31Z

src/hotspot/share/memory/guardedMemory.hpp

@@ -303,9 +303,9 @@ class GuardedMemory : StackObj { // Wrapper on stack
   * @param len the length of the copy
   * @param tag optional general purpose tag (see GuardedMemory::get_tag())
   *
-   * @return guarded wrapped memory pointer to the user area, or NULL if OOM.
+   * @return guarded wrapped memory pointer to the user area, or nullptr if OOM.


nullptr => null?

openjdk · 2023-01-26T09:40:14Z

@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:

8301070: Replace NULL with nullptr in share/memory/

Reviewed-by: stefank, stuefe

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 116 new commits pushed to the master branch:

64ddf95: 8299858: [Metrics] Swap memory limit reported incorrectly when too large
28545dc: 8300247: Harden C1 xchg on AArch64 and PPC
3f63381: 8300913: ZGC: assert(to_addr != 0) failed: Should be forwarded
da80e7a: 8300962: Parallel: Remove PSParallelCompact::_total_invocations
7725fe8: 8299953: Merge ContiguousSpaceDCTOC into DirtyCardToOopClosure
a9b8acb: 8300652: Parallel: Refactor oop marking stack in Full GC
15a1488: 8297437: javadoc cannot link to old docs (with old style anchors)
b0376a5: 8301069: Replace NULL with nullptr in share/libadt/
7328182: 8300958: Parallel: Remove unused MutableNUMASpace::capacity_in_words
30cb305: 8292170: Convert CodeRootSetTable to use ResourceHashtable
... and 106 more: https://git.openjdk.org/jdk/compare/e326b86d37cec3b395b88598cf30ce4239732a15...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.

tstuefe

Metaspace changes are good.

tstuefe · 2023-01-26T09:48:06Z

src/hotspot/share/memory/metaspace/blockTree.hpp

    for (;;) {
      DEBUG_ONLY(check_node(insertion_point);)
      if (n->_word_size == insertion_point->_word_size) {
-        add_to_list(n, insertion_point); // parent stays NULL in this case.
+        add_to_list(n, insertion_point); // parent stays null in this case.


Small nit. Do we have a unified naming scheme for comments?

"null" reads like a java null. I prefer keeping NULL in comments.

Small nit. Do we have a unified naming scheme for comments?

Yeah, I forgot to update the PR message with all of the info. If you check now you can see what's been decided upon. The discussions can be found in previous PRs, I can link to them if you're curious.

"null" reads like a java null. I prefer keeping NULL in comments.

That's true, but this probably can be inferred from context which one is meant quite easily? I'd be more keen on explicitly saying that something is a Java null.

FWIW, from fixing these reviews I've never seen us referring to a Java null when we meant a C++ nullptr.

jdksjolen · 2023-01-26T16:28:27Z

/integrate

Passes tests and two approvals (with stefank's suggested fixes included), integrating.

openjdk · 2023-01-26T16:30:37Z

Going to push as commit d98a323.
Since your change was applied there have been 119 commits pushed to the master branch:

315398c: 8221785: Let possibly_parallel_threads_do cover the same threads as threads_do
14114c2: 8301005: Clean up Copy::conjoint_*_atomic on windows
973f741: 8300968: Accessorize raw oop load in DeadCounterClosure
64ddf95: 8299858: [Metrics] Swap memory limit reported incorrectly when too large
28545dc: 8300247: Harden C1 xchg on AArch64 and PPC
3f63381: 8300913: ZGC: assert(to_addr != 0) failed: Should be forwarded
da80e7a: 8300962: Parallel: Remove PSParallelCompact::_total_invocations
7725fe8: 8299953: Merge ContiguousSpaceDCTOC into DirtyCardToOopClosure
a9b8acb: 8300652: Parallel: Refactor oop marking stack in Full GC
15a1488: 8297437: javadoc cannot link to old docs (with old style anchors)
... and 109 more: https://git.openjdk.org/jdk/compare/e326b86d37cec3b395b88598cf30ce4239732a15...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-01-26T16:30:50Z

@jdksjolen Pushed as commit d98a323.

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

Replace NULL with nullptr in share/memory/

81e1a38

openjdk bot added serviceability serviceability-dev@openjdk.org hotspot hotspot-dev@openjdk.org labels Jan 25, 2023

jdksjolen commented Jan 25, 2023

View reviewed changes

Fix manual issue

def9b5f

jdksjolen marked this pull request as ready for review January 25, 2023 15:11

openjdk bot added the rfr Pull request is ready for review label Jan 25, 2023

stefank approved these changes Jan 26, 2023

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Jan 26, 2023

tstuefe approved these changes Jan 26, 2023

View reviewed changes

Fix stefank's comments

1b09b9a

openjdk bot added the integrated Pull request has been integrated label Jan 26, 2023

openjdk bot closed this Jan 26, 2023

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jan 26, 2023

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JDK-8301070: Replace NULL with nullptr in share/memory/ #12185

JDK-8301070: Replace NULL with nullptr in share/memory/ #12185

jdksjolen commented Jan 25, 2023 •

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JDK-8301070: Replace NULL with nullptr in share/memory/ #12185

JDK-8301070: Replace NULL with nullptr in share/memory/ #12185

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