diff options
| -rw-r--r-- | src/reflect/scala/reflect/internal/Definitions.scala | 22 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/internal/Mirrors.scala | 13 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/internal/Scopes.scala | 6 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/internal/StdNames.scala | 2 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/internal/Symbols.scala | 9 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/runtime/JavaMirrors.scala | 31 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/runtime/JavaUniverse.scala | 61 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/runtime/SymbolLoaders.scala | 36 |
8 files changed, 146 insertions, 34 deletions
diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala index 99aad4f057..e8fea43758 100644 --- a/src/reflect/scala/reflect/internal/Definitions.scala +++ b/src/reflect/scala/reflect/internal/Definitions.scala @@ -1180,10 +1180,17 @@ trait Definitions extends api.StandardDefinitions { } lazy val AnnotationDefaultAttr: ClassSymbol = { - val attr = enterNewClass(RuntimePackageClass, tpnme.AnnotationDefaultATTR, List(AnnotationClass.tpe)) - // This attribute needs a constructor so that modifiers in parsed Java code make sense - attr.info.decls enter attr.newClassConstructor(NoPosition) - attr + val sym = RuntimePackageClass.newClassSymbol(tpnme.AnnotationDefaultATTR, NoPosition, 0L) + sym setInfo ClassInfoType(List(AnnotationClass.tpe), newScope, sym) + RuntimePackageClass.info.decls.toList.filter(_.name == sym.name) match { + case existing :: _ => + existing.asInstanceOf[ClassSymbol] + case _ => + RuntimePackageClass.info.decls enter sym + // This attribute needs a constructor so that modifiers in parsed Java code make sense + sym.info.decls enter sym.newClassConstructor(NoPosition) + sym + } } private def fatalMissingSymbol(owner: Symbol, name: Name, what: String = "member") = { @@ -1388,10 +1395,13 @@ trait Definitions extends api.StandardDefinitions { else flatNameString(etp.typeSymbol, '.') } + // documented in JavaUniverse.init def init() { if (isInitialized) return - // force initialization of every symbol that is synthesized or hijacked by the compiler - val _ = symbolsNotPresentInBytecode + ObjectClass.initialize + ScalaPackageClass.initialize + val forced1 = symbolsNotPresentInBytecode + val forced2 = NoSymbol isInitialized = true } //init diff --git a/src/reflect/scala/reflect/internal/Mirrors.scala b/src/reflect/scala/reflect/internal/Mirrors.scala index 4c2995b676..e122fa498b 100644 --- a/src/reflect/scala/reflect/internal/Mirrors.scala +++ b/src/reflect/scala/reflect/internal/Mirrors.scala @@ -250,6 +250,19 @@ trait Mirrors extends api.Mirrors { RootClass.info.decls enter EmptyPackage RootClass.info.decls enter RootPackage + if (rootOwner != NoSymbol) { + // synthetic core classes are only present in root mirrors + // because Definitions.scala, which initializes and enters them, only affects rootMirror + // therefore we need to enter them manually for non-root mirrors + definitions.syntheticCoreClasses foreach (theirSym => { + val theirOwner = theirSym.owner + assert(theirOwner.isPackageClass, s"theirSym = $theirSym, theirOwner = $theirOwner") + val ourOwner = staticPackage(theirOwner.fullName).moduleClass + val ourSym = theirSym // just copy the symbol into our branch of the symbol table + ourOwner.info.decls enterIfNew ourSym + }) + } + initialized = true } } diff --git a/src/reflect/scala/reflect/internal/Scopes.scala b/src/reflect/scala/reflect/internal/Scopes.scala index 1060b3a99c..b7a1681838 100644 --- a/src/reflect/scala/reflect/internal/Scopes.scala +++ b/src/reflect/scala/reflect/internal/Scopes.scala @@ -139,6 +139,12 @@ trait Scopes extends api.Scopes { self: SymbolTable => enter(sym) } + def enterIfNew[T <: Symbol](sym: T): T = { + val existing = lookupEntry(sym.name) + if (existing == null) enter(sym) + else existing.sym.asInstanceOf[T] + } + private def createHash() { hashtable = new Array[ScopeEntry](HASHSIZE) enterAllInHash(elems) diff --git a/src/reflect/scala/reflect/internal/StdNames.scala b/src/reflect/scala/reflect/internal/StdNames.scala index af26253802..c39efa26fa 100644 --- a/src/reflect/scala/reflect/internal/StdNames.scala +++ b/src/reflect/scala/reflect/internal/StdNames.scala @@ -273,6 +273,8 @@ trait StdNames { final val SourceFileATTR: NameType = "SourceFile" final val SyntheticATTR: NameType = "Synthetic" + final val scala_ : NameType = "scala" + def dropSingletonName(name: Name): TypeName = (name dropRight SINGLETON_SUFFIX.length).toTypeName def singletonName(name: Name): TypeName = (name append SINGLETON_SUFFIX).toTypeName def implClassName(name: Name): TypeName = (name append IMPL_CLASS_SUFFIX).toTypeName diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala index 868913c82f..858d6cf618 100644 --- a/src/reflect/scala/reflect/internal/Symbols.scala +++ b/src/reflect/scala/reflect/internal/Symbols.scala @@ -3341,10 +3341,11 @@ trait Symbols extends api.Symbols { self: SymbolTable => def name = nme.NO_NAME override def name_=(n: Name) = abort("Cannot set NoSymbol's name to " + n) - synchronized { - setInfo(NoType) - privateWithin = this - } + // Syncnote: no need to synchronize this, because NoSymbol's initialization is triggered by JavaUniverse.init + // which is called in universe's constructor - something that's inherently single-threaded + setInfo(NoType) + privateWithin = this + override def info_=(info: Type) = { infos = TypeHistory(1, NoType, null) unlock() diff --git a/src/reflect/scala/reflect/runtime/JavaMirrors.scala b/src/reflect/scala/reflect/runtime/JavaMirrors.scala index 2cdacde900..487da2eb4b 100644 --- a/src/reflect/scala/reflect/runtime/JavaMirrors.scala +++ b/src/reflect/scala/reflect/runtime/JavaMirrors.scala @@ -44,16 +44,6 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni trait JavaClassCompleter extends FlagAssigningCompleter - def init() = { - definitions.AnyValClass // force it. - - // establish root association to avoid cyclic dependency errors later - rootMirror.classToScala(classOf[java.lang.Object]).initialize - - // println("initializing definitions") - definitions.init() - } - def runtimeMirror(cl: ClassLoader): Mirror = mirrors get cl match { case Some(WeakReference(m)) => m case _ => createMirror(rootMirror.RootClass, cl) @@ -1280,11 +1270,6 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni case _ => abort(s"${sym}.enclosingRootClass = ${sym.enclosingRootClass}, which is not a RootSymbol") } - private lazy val syntheticCoreClasses: Map[(String, Name), Symbol] = { - def mapEntry(sym: Symbol): ((String, Name), Symbol) = (sym.owner.fullName, sym.name) -> sym - Map() ++ (definitions.syntheticCoreClasses map mapEntry) - } - /** 1. If `owner` is a package class (but not the empty package) and `name` is a term name, make a new package * <owner>.<name>, otherwise return NoSymbol. * Exception: If owner is root and a java class with given name exists, create symbol in empty package instead @@ -1301,13 +1286,15 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni if (name.isTermName && !owner.isEmptyPackageClass) return mirror.makeScalaPackage( if (owner.isRootSymbol) name.toString else owner.fullName+"."+name) - syntheticCoreClasses get ((owner.fullName, name)) foreach { tsym => - // synthetic core classes are only present in root mirrors - // because Definitions.scala, which initializes and enters them, only affects rootMirror - // therefore we need to enter them manually for non-root mirrors - if (mirror ne thisUniverse.rootMirror) owner.info.decls enter tsym - return tsym - } + if (name == tpnme.AnyRef && owner.owner.isRoot && owner.name == tpnme.scala_) + // when we synthesize the scala.AnyRef symbol, we need to add it to the scope of the scala package + // the problem is that adding to the scope implies doing something like `owner.info.decls enter anyRef` + // which entails running a completer for the scala package + // which will try to unpickle the stuff in scala/package.class + // which will transitively load scala.AnyRef + // which doesn't exist yet, because it hasn't been added to the scope yet + // this missing hook ties the knot without introducing synchronization problems like before + return definitions.AnyRefClass } info("*** missing: "+name+"/"+name.isTermName+"/"+owner+"/"+owner.hasPackageFlag+"/"+owner.info.decls.getClass) super.missingHook(owner, name) diff --git a/src/reflect/scala/reflect/runtime/JavaUniverse.scala b/src/reflect/scala/reflect/runtime/JavaUniverse.scala index 06a7db6289..8f1c1967e0 100644 --- a/src/reflect/scala/reflect/runtime/JavaUniverse.scala +++ b/src/reflect/scala/reflect/runtime/JavaUniverse.scala @@ -27,4 +27,65 @@ class JavaUniverse extends internal.SymbolTable with ReflectSetup with runtime.S } with internal.TreeInfo init() + + // ======= Initialization of runtime reflection ======= + // + // This doc describes the carefully laid out sequence of actions used to initialize reflective universes. + // + // Before reading the text below, read up the section Mirrors in the reflection pre-SIP + // https://docs.google.com/document/d/1nAwSw4TmMplsIlzh2shYLUJ5mVh3wndDa1Zm1H6an9A/edit. + // Take an especially good look at Figure 2, because it illustrates fundamental principles underlying runtime reflection: + // 1) For each universe we have one mirror per classloader + // 2) Package symbols are per-mirror + // 3) Other symbols are per-universe, which means that a symbol (e.g. Seq on the picture) might be shared between multiple owners + // + // Main challenges that runtime reflection presents wrt initialization are: + // 1) Extravagant completion scheme that enters package members on-demand rather than a result of scanning a directory with class files. + // (That's a direct consequence of the fact that in general case we can't enumerate all classes in a classloader). + // 2) Presence of synthetic symbols that aren't loaded by normal means (from classfiles) but are synthesized on-the-fly, + // and the necessity to propagate these synthetic symbols from rootMirror to other mirrors, + // complicated by the fact that such symbols depend on normal symbols (e.g. AnyRef depends on Object). + // 3) Necessity to remain thread-safe, which limits our options related to lazy initialization + // (E.g. we cannot use missingHook to enter synthetic symbols, because that's thread-unsafe). + // + // Directly addressing the challenge #3, we create all synthetic symbols fully in advance during init(). + // However, it's not that simple as just calling definitions.symbolsNotPresentInBytecode. + // Before doing that, we need to first initialize ObjectClass, then ScalaPackageClass, and only then deal with synthetics. + // Below you can find a detailed explanation for that. + // + // ### Why ScalaPackageClass? ### + // + // Forcing ScalaPackageClass first thing during startup is important, because syntheticCoreClasses such as AnyRefClass + // need to be entered into ScalaPackageClass, which entails calling ScalaPackageClass.info.decls.enter. + // If ScalaPackageClass isn't initialized by that moment, the following will happen for runtime reflection: + // 1) Initialization of ScalaPackageClass will trigger unpickling. + // 2) Unpickling will need to load some auxiliary types such as, for example, String. + // 3) To load String, runtime reflection will call mirrorDefining(classOf[String]). + // 4) This, in turn, will call runtimeMirror(classOf[String].getClassLoader). + // 5) For some classloader configurations, the resulting mirror will be different from rootMirror. + // 6) In that case, initialization of the resulting mirror will try to import definitions.syntheticCoreClasses into the mirror. + // 7) This will force all the lazy vals corresponding to syntheticCoreClasses. + // 8) By that time, the completer of ScalaPackageClass will have already called setInfo on ScalaPackageClass, so there won't be any stack overflow. + // + // So far so good, no crashes, no problems, right? Not quite. + // If forcing of ScalaPackageClass was called by a syntheticCoreClasses lazy val, + // then this lazy val will be entered twice: once during step 7 and once when returning from the original call. + // To avoid this we need to initialize ScalaPackageClass prior to other synthetics. + // + // ### Why ObjectClass? ### + // + // 1) As explained in JavaMirrors.missingHook, initialization of ScalaPackageClass critically depends on AnyRefClass. + // 2) AnyRefClass is defined as "lazy val AnyRefClass = newAlias(ScalaPackageClass, tpnme.AnyRef, ObjectTpe)", + // which means that initialization of AnyRefClass depends on ObjectClass. + // 3) ObjectClass is defined as "lazy val ObjectClass = getRequiredClass(sn.Object.toString)", + // which means that under some classloader configurations (see JavaMirrors.missingHook for more details) + // dereferencing ObjectClass might trigger an avalanche of initializations calling back into AnyRefClass + // while another AnyRefClass initializer is still on stack. + // 4) That will lead to AnyRefClass being entered two times (once when the recursive call returns and once when the original one returns) + // 5) That will crash PackageScope.enter that helpfully detects double-enters. + // + // Therefore, before initializing ScalaPackageClass, we must pre-initialize ObjectClass + def init() { + definitions.init() + } } diff --git a/src/reflect/scala/reflect/runtime/SymbolLoaders.scala b/src/reflect/scala/reflect/runtime/SymbolLoaders.scala index 3e149c1fe0..706572ba2b 100644 --- a/src/reflect/scala/reflect/runtime/SymbolLoaders.scala +++ b/src/reflect/scala/reflect/runtime/SymbolLoaders.scala @@ -70,6 +70,25 @@ private[reflect] trait SymbolLoaders { self: SymbolTable => class PackageScope(pkgClass: Symbol) extends Scope(initFingerPrints = -1L) // disable fingerprinting as we do not know entries beforehand with SynchronizedScope { assert(pkgClass.isType) + + // materializing multiple copies of the same symbol in PackageScope is a very popular bug + // this override does its best to guard against it + override def enter[T <: Symbol](sym: T): T = { + // workaround for SI-7728 + if (isCompilerUniverse) super.enter(sym) + else { + val existing = super.lookupEntry(sym.name) + assert(existing == null || existing.sym.isMethod, s"pkgClass = $pkgClass, sym = $sym, existing = $existing") + super.enter(sym) + } + } + + override def enterIfNew[T <: Symbol](sym: T): T = { + val existing = super.lookupEntry(sym.name) + if (existing == null) enter(sym) + else existing.sym.asInstanceOf[T] + } + // disable fingerprinting as we do not know entries beforehand private val negatives = mutable.Set[Name]() // Syncnote: Performance only, so need not be protected. override def lookupEntry(name: Name): ScopeEntry = { @@ -95,8 +114,21 @@ private[reflect] trait SymbolLoaders { self: SymbolTable => val module = origOwner.info decl name.toTermName assert(clazz != NoSymbol) assert(module != NoSymbol) - pkgClass.info.decls enter clazz - pkgClass.info.decls enter module + // currentMirror.mirrorDefining(cls) might side effect by entering symbols into pkgClass.info.decls + // therefore, even though in the beginning of this method, super.lookupEntry(name) returned null + // entering clazz/module now will result in a double-enter assertion in PackageScope.enter + // here's how it might happen + // 1) we are the rootMirror + // 2) cls.getClassLoader is different from our classloader + // 3) mirrorDefining(cls) looks up a mirror corresponding to that classloader and cannot find it + // 4) mirrorDefining creates a new mirror + // 5) that triggers Mirror.init() of the new mirror + // 6) that triggers definitions.syntheticCoreClasses + // 7) that might materialize symbols and enter them into our scope (because syntheticCoreClasses live in rootMirror) + // 8) now we come back here and try to enter one of the now entered symbols => BAM! + // therefore we use enterIfNew rather than just enter + enterIfNew(clazz) + enterIfNew(module) (clazz, module) } debugInfo(s"created $module/${module.moduleClass} in $pkgClass") |