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JDK-8244601: Cleanup support for upcall handles #154

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@mcimadamore mcimadamore commented May 7, 2020

This patch removes the SystemABI::freeUpcallStub routine and, in its place, allows SystemABI::upcallHandle to return a stub segment which can be explicitly closed by the user.

I think having one less method in SystemABI is cleaner - but I'm not 100% sure that using a segment as the return type is the way to go; I found myself split between returning MemoryAddress and MemorySegment while writing this patch. I ultimately went for MemorySegment because I think it makes idiomatic code a tad cleaner (look at StdLibTest).

When writing this I also wondered if we couldn't benefit from a separate abstraction for callbacks - something like:

interface UpcallHandle extends AutoCloseable {
   MethodHandle handle();
   MemoryAddress address();
   void close();

And then teach SystemABI about this carrier (the translation into a raw address should be relatively painless). But then we'd still need to support cases where the function pointer is obtained through another native call (in which case the carrier will just be MemoryAddress). So I'm not sure in the end having this additional abstraction will change things significantly compared to just having a segment and have the user calling baseAddress.

That said, I'm open to suggestions if people feel strongly one way or another.


  • Change must not contain extraneous whitespace
  • Change must be properly reviewed



  • Athijegannathan Sundararajan (sundar - Committer)
  • Jorn Vernee (jvernee - Committer)


$ git fetch pull/154/head:pull/154
$ git checkout pull/154

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@bridgekeeper bridgekeeper bot commented May 7, 2020

👋 Welcome back mcimadamore! A progress list of the required criteria for merging this PR into foreign-abi will be added to the body of your pull request.

@openjdk openjdk bot added the rfr label May 7, 2020
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@openjdk openjdk bot commented May 7, 2020

@mcimadamore This change now passes all automated pre-integration checks, type /integrate in a new comment to proceed. After integration, the commit message will be:

JDK-8244601: Cleanup support for upcall handles

Reviewed-by: sundar, jvernee
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@openjdk openjdk bot added the ready label May 7, 2020
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@JornVernee JornVernee left a comment

Looks good!

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@mcimadamore mcimadamore commented May 7, 2020


@openjdk openjdk bot closed this May 7, 2020
@openjdk openjdk bot added integrated and removed ready rfr labels May 7, 2020
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@openjdk openjdk bot commented May 7, 2020

Pushed as commit d8f37ce.

@mcimadamore mcimadamore deleted the callbackSegment branch May 15, 2020
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