8324809: compiler can crash with SOE while proving if two recursive types are disjoint #19194

vicente-romero-oracle · 2024-05-11T22:18:12Z

javac is crashing with SOE while compiling code like:

class Criteria<B extends Builder<? extends Criteria>> {
    public <D extends Builder<E>, E extends Criteria<D>> D builder() {
        return (D) new Builder<>();
    }

}

class Builder<C extends Criteria<? extends Builder<C>>> {}

here while attributing: return (D)new Builder<>(); the compiler is trying to prove that: Builder<C> is castable to D, then as the upper bound of D is Builder<E>, we need to check if Builder<C> is castable to Builder<E>. Then the next step is to try to check if type variables C and E are disjoint. During this process is when the compiler gets out of resources given that

E <: Criteria
D <: Builder here we have E again and we start over in an infinite loop,

Here the proposal is to detect cycles in the type arguments graph and accept these type of casts if we find a cycle and thus can't prove if two types are disjoint,

TIA

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JDK-8324809: compiler can crash with SOE while proving if two recursive types are disjoint (Bug - P3)

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Maurizio Cimadamore (@mcimadamore - Reviewer)

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…ypes are disjoint

bridgekeeper · 2024-05-11T22:18:46Z

👋 Welcome back vromero! 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 · 2024-05-11T22:19:21Z

@vicente-romero-oracle This change now passes all automated pre-integration checks.

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8324809: compiler can crash with SOE while proving if two recursive types are disjoint

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da9c23a: 8325384: sun/security/ssl/SSLSessionImpl/ResumptionUpdateBoundValues.java failing intermittently when main thread is a virtual thread
dc184f1: 8324649: Shenandoah: replace implementation of free set
2599151: 8331202: Support for Duration until another Instant
6f7ddbe: 8260633: [macos] java/awt/dnd/MouseEventAfterStartDragTest/MouseEventAfterStartDragTest.html test failed
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a33cb90: 8332098: Add missing @ since tags to jdk.jdi
910d77b: 8331953: ubsan: metaspaceShared.cpp:1305:57: runtime error: applying non-zero offset 12849152 to null pointer
f9f8d0b: 8332101: Add an @since to StandardOperation:REMOVE in jdk.dynalink
f398cd2: 8331575: C2: crash when ConvL2I is split thru phi at LongCountedLoop
96c5c3f: 8329998: Remove double initialization for parts of small TypeArrays in ZObjArrayAllocator
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openjdk · 2024-05-11T22:19:43Z

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mlbridge · 2024-05-11T22:22:31Z

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mcimadamore · 2024-05-16T16:44:10Z

src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java

- erasure(t.getUpperBound()) :
- visit(t.getUpperBound());
- return rewriteAsWildcardType(bound, t, EXTENDS);
+ if (seen.add(t)) {


IIRC, this code is called by Types.isCastable, in an attempt to do some fancy logic (outside the spec) which allow to determine whether two types are disjoint or not. To do this, the code attempts to rewrite occurrences of type-variables using wildcards. So, in some cases the logic fails with SOE - so that result should lead to the consequence that we don't know whether the types are disjoint or not, but, since we're outside the scope of the spec, we need to treat them as not disjoint (e.g. the cast should be possible and we gave up proving that it should NOT be possible).

So, I'm afraid that return t here is going to make this method stricter than intended, which will lead javac to think that the types are in fact disjoint, and that will result in a compiler error. I wonder if we should we return a ? instead?

mcimadamore · 2024-05-16T16:46:09Z

src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java

@@ -4734,6 +4734,10 @@ class Rewriter extends UnaryVisitor<Type> {

 boolean high;
 boolean rewriteTypeVars;
+ // map to avoid visiting same type argument twice, like in Foo<T>.Bar<T>
+ Map<Type, Type> argMap = new HashMap<>();


Do we need to use both a map and a set, or can we just use the map?

I think yes and in any case the code is more readable, me thinks, with both than using only one

mcimadamore

Looks good

vicente-romero-oracle · 2024-05-17T14:14:59Z

/integrate

openjdk · 2024-05-17T14:16:14Z

Going to push as commit 39a55e9.
Since your change was applied there have been 419 commits pushed to the master branch:

b7ae0ae: 8328572: JFR: Use Class.forPrimitiveName(String)
e611151: 8331281: RISC-V: C2: Support vector-scalar and vector-immediate bitwise logic instructions
44bdf99: 8332239: Improve CSS for block tags
9bb6169: 8317621: --add-script should support JavaScript modules
4eb1eaf: 8329617: Update stylesheet for specs and tool documentation
d4c2edf: 8331855: Convert jdk.jdeps jdeprscan and jdeps to use the Classfile API
beeffd4: 8332109: Convert remaining tests using com.sun.tools.classfile to ClassFile API
e0d1c4b: 8321428: Deprecate for removal the package java.beans.beancontext
0b0445b: 8331724: Refactor j.l.constant implementation to internal package
d84a8fd: 8332327: Return _methods_jmethod_ids field back in VMStructs
... and 409 more: https://git.openjdk.org/jdk/compare/76cbe4883b5f53843e5140eee2145011fec67e4c...master

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openjdk · 2024-05-17T14:16:19Z

@vicente-romero-oracle Pushed as commit 39a55e9.

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8324809: compiler can crash with SOE while proving if two recursive t…

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…ypes are disjoint

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8324809: compiler can crash with SOE while proving if two recursive types are disjoint #19194

8324809: compiler can crash with SOE while proving if two recursive types are disjoint #19194

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8324809: compiler can crash with SOE while proving if two recursive types are disjoint #19194

8324809: compiler can crash with SOE while proving if two recursive types are disjoint #19194

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vicente-romero-oracle commented May 11, 2024 • edited by openjdk bot

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