diff options
Diffstat (limited to 'src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala')
| -rw-r--r-- | src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala | 60 |
1 files changed, 45 insertions, 15 deletions
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala index b94208c1a5..add2c5ffe6 100644 --- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala +++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala @@ -30,17 +30,17 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { def genSynchronized(tree: Apply, expectedType: BType): BType = { val Apply(fun, args) = tree - val monitor = locals.makeLocal(ObjectReference, "monitor") + val monitor = locals.makeLocal(ObjectRef, "monitor") val monCleanup = new asm.Label // if the synchronized block returns a result, store it in a local variable. // Just leaving it on the stack is not valid in MSIL (stack is cleaned when leaving try-blocks). val hasResult = (expectedType != UNIT) - val monitorResult: Symbol = if (hasResult) locals.makeLocal(tpeTK(args.head), "monitorResult") else null; + val monitorResult: Symbol = if (hasResult) locals.makeLocal(tpeTK(args.head), "monitorResult") else null /* ------ (1) pushing and entering the monitor, also keeping a reference to it in a local var. ------ */ genLoadQualifier(fun) - bc dup ObjectReference + bc dup ObjectRef locals.store(monitor) emit(asm.Opcodes.MONITORENTER) @@ -73,9 +73,11 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { /* ------ (4) exception-handler version of monitor-exit code. * Reached upon abrupt termination of (2). * Protected by whatever protects the whole synchronized expression. + * null => "any" exception in bytecode, like we emit for finally. + * Important not to use j/l/Throwable which dooms the method to a life of interpretation! (SD-233) * ------ */ - protect(startProtected, endProtected, currProgramPoint(), ThrowableReference) + protect(startProtected, endProtected, currProgramPoint(), null) locals.load(monitor) emit(asm.Opcodes.MONITOREXIT) emit(asm.Opcodes.ATHROW) @@ -184,7 +186,7 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { for (CaseDef(pat, _, caseBody) <- catches) yield { pat match { case Typed(Ident(nme.WILDCARD), tpt) => NamelessEH(tpeTK(tpt).asClassBType, caseBody) - case Ident(nme.WILDCARD) => NamelessEH(ThrowableReference, caseBody) + case Ident(nme.WILDCARD) => NamelessEH(jlThrowableRef, caseBody) case Bind(_, _) => BoundEH (pat.symbol, caseBody) } } @@ -213,7 +215,7 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { * please notice `tmp` has type tree.tpe, while `earlyReturnVar` has the method return type. * Because those two types can be different, dedicated vars are needed. */ - val tmp = if (guardResult) locals.makeLocal(tpeTK(tree), "tmp") else null; + val tmp = if (guardResult) locals.makeLocal(tpeTK(tree), "tmp") else null /* * upon early return from the try-body or one of its EHs (but not the EH-version of the finally-clause) @@ -236,6 +238,34 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { val endTryBody = currProgramPoint() bc goTo postHandlers + /** + * A return within a `try` or `catch` block where a `finally` is present ("early return") + * emits a store of the result to a local, jump to a "cleanup" version of the `finally` block, + * and sets `shouldEmitCleanup = true` (see [[PlainBodyBuilder.genReturn]]). + * + * If the try-catch is nested, outer `finally` blocks need to be emitted in a cleanup version + * as well, so the `shouldEmitCleanup` variable remains `true` until the outermost `finally`. + * Nested cleanup `finally` blocks jump to the next enclosing one. For the outermost, we emit + * a read of the local variable, a return, and we set `shouldEmitCleanup = false` (see + * [[pendingCleanups]]). + * + * Now, assume we have + * + * try { return 1 } finally { + * try { println() } finally { println() } + * } + * + * Here, the outer `finally` needs a cleanup version, but the inner one does not. The method + * here makes sure that `shouldEmitCleanup` is only propagated outwards, not inwards to + * nested `finally` blocks. + */ + def withFreshCleanupScope(body: => Unit) = { + val savedShouldEmitCleanup = shouldEmitCleanup + shouldEmitCleanup = false + body + shouldEmitCleanup = savedShouldEmitCleanup || shouldEmitCleanup + } + /* ------ (2) One EH for each case-clause (this does not include the EH-version of the finally-clause) * An EH in (2) is reached upon abrupt termination of (1). * An EH in (2) is protected by: @@ -244,8 +274,7 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { * ------ */ - for (ch <- caseHandlers) { - + for (ch <- caseHandlers) withFreshCleanupScope { // (2.a) emit case clause proper val startHandler = currProgramPoint() var endHandler: asm.Label = null @@ -275,9 +304,13 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { protect(startTryBody, endTryBody, startHandler, excType) // (2.c) emit jump to the program point where the finally-clause-for-normal-exit starts, or in effect `after` if no finally-clause was given. bc goTo postHandlers - } + // Need to save the state of `shouldEmitCleanup` at this point: while emitting the first + // version of the `finally` block below, the variable may become true. But this does not mean + // that we need a cleanup version for the current block, only for the enclosing ones. + val currentFinallyBlockNeedsCleanup = shouldEmitCleanup + /* ------ (3.A) The exception-handler-version of the finally-clause. * Reached upon abrupt termination of (1) or one of the EHs in (2). * Protected only by whatever protects the whole try-catch-finally expression. @@ -286,11 +319,11 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { // a note on terminology: this is not "postHandlers", despite appearances. // "postHandlers" as in the source-code view. And from that perspective, both (3.A) and (3.B) are invisible implementation artifacts. - if (hasFinally) { + if (hasFinally) withFreshCleanupScope { nopIfNeeded(startTryBody) val finalHandler = currProgramPoint() // version of the finally-clause reached via unhandled exception. protect(startTryBody, finalHandler, finalHandler, null) - val Local(eTK, _, eIdx, _) = locals(locals.makeLocal(ThrowableReference, "exc")) + val Local(eTK, _, eIdx, _) = locals(locals.makeLocal(jlThrowableRef, "exc")) bc.store(eIdx, eTK) emitFinalizer(finalizer, null, isDuplicate = true) bc.load(eIdx, eTK) @@ -314,14 +347,11 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { // this is not "postHandlers" either. // `shouldEmitCleanup` can be set, and at the same time this try expression may lack a finally-clause. // In other words, all combinations of (hasFinally, shouldEmitCleanup) are valid. - if (hasFinally && shouldEmitCleanup) { - val savedInsideCleanup = insideCleanupBlock - insideCleanupBlock = true + if (hasFinally && currentFinallyBlockNeedsCleanup) { markProgramPoint(finCleanup) // regarding return value, the protocol is: in place of a `return-stmt`, a sequence of `adapt, store, jump` are inserted. emitFinalizer(finalizer, null, isDuplicate = true) pendingCleanups() - insideCleanupBlock = savedInsideCleanup } /* ------ (4) finally-clause-for-normal-nonEarlyReturn-exit |