JDK-8326974: ODR violation in macroAssembler_aarch64.cpp #18056

theRealAph · 2024-02-29T09:47:11Z

This is a slightly different patch from the one suggested by the bug reporter. It doesn't make any sense to export those classes globally, so I've given them internal linkage.

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Issue

JDK-8326974: ODR violation in macroAssembler_aarch64.cpp (Bug - P4)

Reviewers

Andrew Dinn (@adinn - Reviewer) ⚠️ Review applies to a3fc57b5
Aleksey Shipilev (@shipilev - Reviewer) ⚠️ Review applies to 7f38d070
Guoxiong Li (@lgxbslgx - Committer)

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bridgekeeper · 2024-02-29T09:48:06Z

👋 Welcome back aph! 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 · 2024-02-29T09:48:33Z

@theRealAph The following label will be automatically applied to this pull request:

hotspot

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

mlbridge · 2024-02-29T09:51:01Z

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adinn

Looks good.

openjdk · 2024-02-29T10:25:21Z

@theRealAph 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:

8326974: ODR violation in macroAssembler_aarch64.cpp

Reviewed-by: adinn, shade, gli

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 11 new commits pushed to the master branch:

8d6f784: 8327056: Remove unused static char array in JvmtiAgentList::lookup
43af120: 8326959: Improve JVMCI option help
742c776: 8322743: C2: prevent lock region elimination in OSR compilation
d29cefb: 8326838: JFR: Native mirror events
b8fc418: 8326525: com/sun/tools/attach/BasicTests.java does not verify AgentLoadException case
d9aa1de: 8318605: Enable parallelism in vmTestbase/nsk/stress/stack tests
bbfda65: 8326897: (fs) The utility TestUtil.supportsLinks is wrongly used to check for hard link support
db0e2b8: 8326944: (ch) Minor typo in the ScatteringByteChannel.read(ByteBuffer[] dsts,int offset,int length) javadoc
8f6edd8: 8326975: Parallel: Remove redundant PSOldGen::is_allocated
4302900: 8319673: Few security tests ignore VM flags
... and 1 more: https://git.openjdk.org/jdk/compare/d9ef16dbb6917a4fff7711b32f3dd87611560dd1...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.

TheShermanTanker · 2024-02-29T13:18:00Z

Looks like this is causing Actions failures

shipilev · 2024-02-29T13:25:20Z

I think the patch suggested in bug was better, and in line with Hotspot Style Guide, which says: "Global names must be unique, to avoid One Definition Rule (ODR) violations. A common prefixing scheme for related global names is often used. (This is instead of using namespaces, which are mostly avoided in HotSpot.)"

kimbarrett · 2024-02-29T13:27:59Z

I think the patch suggested in bug was better, and in line with Hotspot Style Guide, which says: "Global names must be unique, to avoid One Definition Rule (ODR) violations. A common prefixing scheme for related global names is often used. (This is instead of using namespaces, which are mostly avoided in HotSpot.)"

See also the section "Namespaces", and in particular the specific admonition against using anonymous namespaces.

adinn · 2024-02-29T13:31:32Z

Egad! the action failure messages on Windows include this:

Linking jvm.dll
jvm.exp : error LNK2001: unresolved external symbol "const anonymous namespace'::Decoder::vftable'" (??_7Decoder@?A0xe77b3496@@6b@)
jvm.exp : error LNK2001: unresolved external symbol "const anonymous namespace'::Patcher::vftable'" (??_7Patcher@?A0xe77b3496@@6b@)

So, clearly something in the guts of the (Windows) build does not like anonymous name spaces.

theRealAph · 2024-02-29T15:41:04Z

I think the patch suggested in bug was better, and in line with Hotspot Style Guide, which says: "Global names must be unique, to avoid One Definition Rule (ODR) violations. A common prefixing scheme for related global names is often used. (This is instead of using namespaces, which are mostly avoided in HotSpot.)"

See also the section "Namespaces", and in particular the specific admonition against using anonymous namespaces.

Mmm, that's a shame. It seems to me that an anonymous namespace is best here, given that the classes should not be visible outside this translation unit, but implementation bugs in debuggers and linkers are a show stopper.

shipilev

Looks fine.

shipilev · 2024-02-29T16:57:44Z

src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp

@@ -148,6 +148,7 @@ extern "C" void disnm(intptr_t p);
 //                 strictly should be 64 bit movz #imm16<<0
 //       110___10100 (i.e. requires insn[31:21] == 11010010100)
 //
+


Is this newline addition necessary?

adinn

Also looks good. If the actions fail with this version then surely it has to be a case of "Houston we have a problem . . . with the actions".

dean-long · 2024-02-29T23:17:54Z

How about making Decoder into a nested class of MacroAssembler? You just need a forward declaration in macroAssembler_aarch64.hpp.

kimbarrett · 2024-03-01T00:37:33Z

I think the patch suggested in bug was better, and in line with Hotspot Style Guide, which says: "Global names must be unique, to avoid One Definition Rule (ODR) violations. A common prefixing scheme for related global names is often used. (This is instead of using namespaces, which are mostly avoided in HotSpot.)"

See also the section "Namespaces", and in particular the specific admonition against using anonymous namespaces.

Mmm, that's a shame. It seems to me that an anonymous namespace is best here, given that the classes should not be visible outside this translation unit, but implementation bugs in debuggers and linkers are a show stopper.

I completely agree :( My experience on a different project was that anonymous namespaces had some significant
benefits, including potentially having such classes treated as implicitly final, with the optimizations that can come
from that.

I haven't looked at how well "modern" debugger versions cope with anonymous namespaces. It seems like problems
there should have been fixed by now - anonymous namespaces are hardly new. I was surprised that the usage proposed
here ran into linker problems though. It would be nice if someone with good windows access could investigate that.

lgxbslgx

LGTM.

TheShermanTanker · 2024-03-01T01:32:23Z

I think the patch suggested in bug was better, and in line with Hotspot Style Guide, which says: "Global names must be unique, to avoid One Definition Rule (ODR) violations. A common prefixing scheme for related global names is often used. (This is instead of using namespaces, which are mostly avoided in HotSpot.)"

See also the section "Namespaces", and in particular the specific admonition against using anonymous namespaces.

Mmm, that's a shame. It seems to me that an anonymous namespace is best here, given that the classes should not be visible outside this translation unit, but implementation bugs in debuggers and linkers are a show stopper.

I completely agree :( My experience on a different project was that anonymous namespaces had some significant benefits, including potentially having such classes treated as implicitly final, with the optimizations that can come from that.

I haven't looked at how well "modern" debugger versions cope with anonymous namespaces. It seems like problems there should have been fixed by now - anonymous namespaces are hardly new. I was surprised that the usage proposed here ran into linker problems though. It would be nice if someone with good windows access could investigate that.

It seemed to me that macOS ARM64 also experienced failures earlier, not just Windows, unless the test failure is unrelated? (I'm not very familiar with the JDK's testing framework)

I could help look into it, since I primarily develop on Windows, but I'd probably need time since I'm a little busy at the moment

theRealAph · 2024-03-01T12:37:32Z

How about making Decoder into a nested class of MacroAssembler? You just need a forward declaration in macroAssembler_aarch64.hpp.

That would have been an excellent thing to do, and I didn't think about it, but please let this patch stand. We've spent enough time on it already, I think.

theRealAph · 2024-03-01T12:38:06Z

/integrate

openjdk · 2024-03-01T12:39:23Z

Going to push as commit b972997.
Since your change was applied there have been 18 commits pushed to the master branch:

437cf35: 8319648: java/lang/SecurityManager tests ignore vm flags
e85265a: 8325361: Make sun.net.www.MessageHeader final
5b75199: 8327022: Parallel: Remove experimental dense prefix calculation
a065eba: 8326496: [test] checkHsErrFileContent support printing hserr in error case
0899b3b: 8326612: Parallel: remove redundant assertion from ScavengeRootsTask
12404a5: 8324790: ifnode::fold_compares_helper cleanup
0d35450: 8327040: Problemlist ActionListenerCalledTwiceTest.java test failing in macos14
8d6f784: 8327056: Remove unused static char array in JvmtiAgentList::lookup
43af120: 8326959: Improve JVMCI option help
742c776: 8322743: C2: prevent lock region elimination in OSR compilation
... and 8 more: https://git.openjdk.org/jdk/compare/d9ef16dbb6917a4fff7711b32f3dd87611560dd1...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-03-01T12:39:29Z

@theRealAph Pushed as commit b972997.

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

stefank · 2024-03-11T14:29:39Z

Egad! the action failure messages on Windows include this:

Linking jvm.dll jvm.exp : error LNK2001: unresolved external symbol "const anonymous namespace'::Decoder::vftable'" (??_7Decoder@?A0xe77b3496@@6b@) jvm.exp : error LNK2001: unresolved external symbol "const anonymous namespace'::Patcher::vftable'" (??_7Patcher@?A0xe77b3496@@6b@)

So, clearly something in the guts of the (Windows) build does not like anonymous name spaces.

FWIW, the make files strip these symbols on Windows (for some reason). I've hit a similar problem when we started to use lambdas in hotspot:
09f5235

JDK-8326974: ODR violation in macroAssembler_aarch64.cpp

a3fc57b

openjdk bot added the rfr Pull request is ready for review label Feb 29, 2024

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openjdk bot added the ready Pull request is ready to be integrated label Feb 29, 2024

JDK-8326974: ODR violation in macroAssembler_aarch64.cpp

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shipilev approved these changes Feb 29, 2024

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adinn reviewed Feb 29, 2024

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JDK-8326974: ODR violation in macroAssembler_aarch64.cpp

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lgxbslgx approved these changes Mar 1, 2024

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openjdk bot added the integrated Pull request has been integrated label Mar 1, 2024

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JDK-8326974: ODR violation in macroAssembler_aarch64.cpp #18056

JDK-8326974: ODR violation in macroAssembler_aarch64.cpp #18056

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