/*******************************************************************************
* Copyright (c) 2000, 2010 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jdt.internal.compiler.flow;
import org.eclipse.jdt.internal.compiler.lookup.FieldBinding;
import org.eclipse.jdt.internal.compiler.lookup.LocalVariableBinding;
public abstract class FlowInfo {
public int tagBits; // REACHABLE by default
public final static int REACHABLE= 0;
public final static int UNREACHABLE= 1;
public final static int NULL_FLAG_MASK= 2;
public final static int UNKNOWN= 0;
public final static int NULL= 1;
public final static int NON_NULL= -1;
public static final UnconditionalFlowInfo DEAD_END; // Represents a dead branch status of initialization
static {
DEAD_END= new UnconditionalFlowInfo();
DEAD_END.tagBits= UNREACHABLE;
}
/**
* Add other inits to this flow info, then return this. The operation semantics are to match as
* closely as possible the application to this flow info of all the operations that resulted
* into otherInits.
*
* @param otherInits other inits to add to this
* @return this, modified according to otherInits information
*/
abstract public FlowInfo addInitializationsFrom(FlowInfo otherInits);
/**
* Compose other inits over this flow info, then return this. The operation semantics are to
* wave into this flow info the consequences of a possible path into the operations that
* resulted into otherInits. The fact that this path may be left unexecuted under peculiar
* conditions results into less specific results than {@link #addInitializationsFrom(FlowInfo)
* addInitializationsFrom}.
*
* @param otherInits other inits to compose over this
* @return this, modified according to otherInits information
*/
abstract public FlowInfo addPotentialInitializationsFrom(FlowInfo otherInits);
public FlowInfo asNegatedCondition() {
return this;
}
public static FlowInfo conditional(FlowInfo initsWhenTrue, FlowInfo initsWhenFalse) {
if (initsWhenTrue == initsWhenFalse)
return initsWhenTrue;
// if (initsWhenTrue.equals(initsWhenFalse)) return initsWhenTrue; -- could optimize if #equals is defined
return new ConditionalFlowInfo(initsWhenTrue, initsWhenFalse);
}
/**
* Check whether a given local variable is known to be unable to gain a definite non null or
* definite null status by the use of an enclosing flow info. The semantics are that if the
* current flow info marks the variable as potentially unknown or else as being both potentially
* null and potentially non null, then it won't ever be promoted as definitely null or
* definitely non null. (It could still get promoted to definite unknown).
*
* @param local the variable to check
* @return true iff this flow info prevents local from being promoted to definite non null or
* definite null against an enclosing flow info
*/
public boolean cannotBeDefinitelyNullOrNonNull(LocalVariableBinding local) {
return isPotentiallyUnknown(local) ||
isPotentiallyNonNull(local) && isPotentiallyNull(local);
}
/**
* Check whether a given local variable is known to be non null, either because it is definitely
* non null, or because is has been tested against non null.
*
* @param local the variable to ckeck
* @return true iff local cannot be null for this flow info
*/
public boolean cannotBeNull(LocalVariableBinding local) {
return isDefinitelyNonNull(local) || isProtectedNonNull(local);
}
/**
* Check whether a given local variable is known to be null, either because it is definitely
* null, or because is has been tested against null.
*
* @param local the variable to ckeck
* @return true iff local can only be null for this flow info
*/
public boolean canOnlyBeNull(LocalVariableBinding local) {
return isDefinitelyNull(local) || isProtectedNull(local);
}
/**
* Return a deep copy of the current instance.
*
* @return a deep copy of this flow info
*/
abstract public FlowInfo copy();
public static UnconditionalFlowInfo initial(int maxFieldCount) {
UnconditionalFlowInfo info= new UnconditionalFlowInfo();
info.maxFieldCount= maxFieldCount;
return info;
}
/**
* Return the flow info that would result from the path associated to the value false for the
* condition expression that generated this flow info. May be this flow info if it is not an
* instance of {@link ConditionalFlowInfo}. May have a side effect on subparts of this flow info
* (subtrees get merged).
*
* @return the flow info associated to the false branch of the condition that generated this
* flow info
*/
abstract public FlowInfo initsWhenFalse();
/**
* Return the flow info that would result from the path associated to the value true for the
* condition expression that generated this flow info. May be this flow info if it is not an
* instance of {@link ConditionalFlowInfo}. May have a side effect on subparts of this flow info
* (subtrees get merged).
*
* @return the flow info associated to the true branch of the condition that generated this flow
* info
*/
abstract public FlowInfo initsWhenTrue();
/**
* Check status of definite assignment for a field.
*/
abstract public boolean isDefinitelyAssigned(FieldBinding field);
/**
* Check status of definite assignment for a local.
*/
public abstract boolean isDefinitelyAssigned(LocalVariableBinding local);
/**
* Check status of definite non-null value for a given local variable.
*
* @param local the variable to ckeck
* @return true iff local is definitely non null for this flow info
*/
public abstract boolean isDefinitelyNonNull(LocalVariableBinding local);
/**
* Check status of definite null value for a given local variable.
*
* @param local the variable to ckeck
* @return true iff local is definitely null for this flow info
*/
public abstract boolean isDefinitelyNull(LocalVariableBinding local);
/**
* Check status of definite unknown value for a given local variable.
*
* @param local the variable to ckeck
* @return true iff local is definitely unknown for this flow info
*/
public abstract boolean isDefinitelyUnknown(LocalVariableBinding local);
/**
* Check status of potential assignment for a field.
*/
abstract public boolean isPotentiallyAssigned(FieldBinding field);
/**
* Check status of potential assignment for a local variable.
*/
abstract public boolean isPotentiallyAssigned(LocalVariableBinding field);
/**
* Check status of potential null assignment for a local. Return true if there is a reasonable
* expectation that the variable be non null at this point.
*
* @param local LocalVariableBinding - the binding for the checked local
* @return true if there is a reasonable expectation that local be non null at this point
*/
public abstract boolean isPotentiallyNonNull(LocalVariableBinding local);
/**
* Check status of potential null assignment for a local. Return true if there is a reasonable
* expectation that the variable be null at this point. This includes the protected null case,
* so as to augment diagnostics, but does not really check that someone deliberately assigned to
* null on any specific path
*
* @param local LocalVariableBinding - the binding for the checked local
* @return true if there is a reasonable expectation that local be null at this point
*/
public abstract boolean isPotentiallyNull(LocalVariableBinding local);
/**
* Return true if the given local may have been assigned to an unknown value.
*
* @param local the local to check
* @return true if the given local may have been assigned to an unknown value
*/
public abstract boolean isPotentiallyUnknown(LocalVariableBinding local);
/**
* Return true if the given local is protected by a test against a non null value.
*
* @param local the local to check
* @return true if the given local is protected by a test against a non null
*/
public abstract boolean isProtectedNonNull(LocalVariableBinding local);
/**
* Return true if the given local is protected by a test against null.
*
* @param local the local to check
* @return true if the given local is protected by a test against null
*/
public abstract boolean isProtectedNull(LocalVariableBinding local);
/**
* Record that a local variable got checked to be non null.
*
* @param local the checked local variable
*/
abstract public void markAsComparedEqualToNonNull(LocalVariableBinding local);
/**
* Record that a local variable got checked to be null.
*
* @param local the checked local variable
*/
abstract public void markAsComparedEqualToNull(LocalVariableBinding local);
/**
* Record a field got definitely assigned.
*/
abstract public void markAsDefinitelyAssigned(FieldBinding field);
/**
* Record a local got definitely assigned to a non-null value.
*/
abstract public void markAsDefinitelyNonNull(LocalVariableBinding local);
/**
* Record a local got definitely assigned to null.
*/
abstract public void markAsDefinitelyNull(LocalVariableBinding local);
/**
* Record a local got definitely assigned.
*/
abstract public void markAsDefinitelyAssigned(LocalVariableBinding local);
/**
* Record a local got definitely assigned to an unknown value.
*/
abstract public void markAsDefinitelyUnknown(LocalVariableBinding local);
/**
* Merge branches using optimized boolean conditions
*/
public static UnconditionalFlowInfo mergedOptimizedBranches(
FlowInfo initsWhenTrue, boolean isOptimizedTrue,
FlowInfo initsWhenFalse, boolean isOptimizedFalse,
boolean allowFakeDeadBranch) {
UnconditionalFlowInfo mergedInfo;
if (isOptimizedTrue) {
if (initsWhenTrue == FlowInfo.DEAD_END && allowFakeDeadBranch) {
mergedInfo= initsWhenFalse.setReachMode(FlowInfo.UNREACHABLE).
unconditionalInits();
} else {
mergedInfo=
initsWhenTrue.addPotentialInitializationsFrom(initsWhenFalse.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
}
} else if (isOptimizedFalse) {
if (initsWhenFalse == FlowInfo.DEAD_END && allowFakeDeadBranch) {
mergedInfo= initsWhenTrue.setReachMode(FlowInfo.UNREACHABLE).
unconditionalInits();
} else {
mergedInfo=
initsWhenFalse.addPotentialInitializationsFrom(initsWhenTrue.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
}
} else {
mergedInfo= initsWhenTrue.
mergedWith(initsWhenFalse.unconditionalInits());
}
return mergedInfo;
}
/**
* Merge if-else branches using optimized boolean conditions
*/
public static UnconditionalFlowInfo mergedOptimizedBranchesIfElse(
FlowInfo initsWhenTrue, boolean isOptimizedTrue,
FlowInfo initsWhenFalse, boolean isOptimizedFalse,
boolean allowFakeDeadBranch, FlowInfo flowInfo) {
UnconditionalFlowInfo mergedInfo;
if (isOptimizedTrue) {
if (initsWhenTrue == FlowInfo.DEAD_END && allowFakeDeadBranch) {
mergedInfo= initsWhenFalse.setReachMode(FlowInfo.UNREACHABLE).
unconditionalInits();
} else {
mergedInfo=
initsWhenTrue.addPotentialInitializationsFrom(initsWhenFalse.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
}
} else if (isOptimizedFalse) {
if (initsWhenFalse == FlowInfo.DEAD_END && allowFakeDeadBranch) {
mergedInfo= initsWhenTrue.setReachMode(FlowInfo.UNREACHABLE).
unconditionalInits();
} else {
mergedInfo=
initsWhenFalse.addPotentialInitializationsFrom(initsWhenTrue.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
}
} else if ((flowInfo.tagBits & FlowInfo.UNREACHABLE) == 0 &&
(initsWhenFalse.tagBits & FlowInfo.UNREACHABLE) != 0 &&
initsWhenTrue != FlowInfo.DEAD_END &&
initsWhenFalse != FlowInfo.DEAD_END) {
// Done when the then branch will always be executed but the condition does not have a boolean
// true or false (i.e if(true), etc) for sure
// We don't do this if both if and else branches themselves are in an unreachable code
// or if any of them is a DEAD_END (e.g. contains 'return' or 'throws')
mergedInfo=
initsWhenTrue.addPotentialInitializationsFrom(initsWhenFalse.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
// if a variable is only initialized in one branch and not initialized in the other,
// then we need to cast a doubt on its initialization in the merged info
mergedInfo.definiteInits&= initsWhenFalse.unconditionalCopy().definiteInits;
} else if ((flowInfo.tagBits & FlowInfo.UNREACHABLE) == 0 &&
(initsWhenTrue.tagBits & FlowInfo.UNREACHABLE) != 0 && initsWhenTrue != FlowInfo.DEAD_END
&& initsWhenFalse != FlowInfo.DEAD_END) {
// Done when the else branch will always be executed but the condition does not have a boolean
// true or false (i.e if(true), etc) for sure
// We don't do this if both if and else branches themselves are in an unreachable code
// or if any of them is a DEAD_END (e.g. contains 'return' or 'throws')
mergedInfo=
initsWhenFalse.addPotentialInitializationsFrom(initsWhenTrue.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
// if a variable is only initialized in one branch and not initialized in the other,
// then we need to cast a doubt on its initialization in the merged info
mergedInfo.definiteInits&= initsWhenTrue.unconditionalCopy().definiteInits;
} else {
mergedInfo= initsWhenTrue.
mergedWith(initsWhenFalse.unconditionalInits());
}
return mergedInfo;
}
/**
* Return REACHABLE if this flow info is reachable, UNREACHABLE else.
*
* @return REACHABLE if this flow info is reachable, UNREACHABLE else
*/
public int reachMode() {
return this.tagBits & UNREACHABLE;
}
/**
* Return a flow info that carries the same information as the result of
* {@link #initsWhenTrue() initsWhenTrue}, but warrantied to be different from this.<br>
* Caveat: side effects on the result may affect components of this.
*
* @return the result of initsWhenTrue or a copy of it
*/
abstract public FlowInfo safeInitsWhenTrue();
/**
* Set this flow info reach mode and return this.
*
* @param reachMode one of {@link #REACHABLE REACHABLE} or {@link #UNREACHABLE UNREACHABLE}
* @return this, with the reach mode set to reachMode
*/
abstract public FlowInfo setReachMode(int reachMode);
/**
* Return the intersection of this and otherInits, that is one of:
* <ul>
* <li>the receiver updated in the following way:
* <ul>
* <li>intersection of definitely assigned variables,
* <li>union of potentially assigned variables,
* <li>similar operations for null,
* </ul>
* <li>or the receiver or otherInits if the other one is non reachable.
* </ul>
* otherInits is not affected, and is not returned either (no need to protect the result).
*
* @param otherInits the flow info to merge with this
* @return the intersection of this and otherInits.
*/
abstract public UnconditionalFlowInfo mergedWith(
UnconditionalFlowInfo otherInits);
/**
* Return a copy of this unconditional flow info, deprived from its null info. {@link #DEAD_END
* DEAD_END} is returned unmodified.
*
* @return a copy of this unconditional flow info deprived from its null info
*/
abstract public UnconditionalFlowInfo nullInfoLessUnconditionalCopy();
public String toString() {
if (this == DEAD_END) {
return "FlowInfo.DEAD_END"; //$NON-NLS-1$
}
return super.toString();
}
/**
* Return a new flow info that holds the same information as this would after a call to
* unconditionalInits, but leaving this info unaffected. Moreover, the result can be modified
* without affecting this.
*
* @return a new flow info carrying this unconditional flow info
*/
abstract public UnconditionalFlowInfo unconditionalCopy();
/**
* Return a new flow info that holds the same information as this would after a call to
* {@link #unconditionalInits() unconditionalInits} followed by the erasure of fields specific
* information, but leaving this flow info unaffected.
*
* @return a new flow info carrying the unconditional flow info for local variables
*/
abstract public UnconditionalFlowInfo unconditionalFieldLessCopy();
/**
* Return a flow info that merges the possible paths of execution described by this flow info.
* In case of an unconditional flow info, return this. In case of a conditional flow info, merge
* branches recursively. Caveat: this may be affected, and modifying the result may affect this.
*
* @return a flow info that merges the possible paths of execution described by this
*/
abstract public UnconditionalFlowInfo unconditionalInits();
/**
* Return a new flow info that holds the same information as this would after a call to
* {@link #unconditionalInits() unconditionalInits}, but leaving this info unaffected. Side
* effects on the result might affect this though (consider it as read only).
*
* @return a flow info carrying this unconditional flow info
*/
abstract public UnconditionalFlowInfo unconditionalInitsWithoutSideEffect();
/**
* Tell the flowInfo that a local variable got marked as non null or null due to comparison with
* null inside an assert expression. This is to prevent over-aggressive code generation for
* subsequent if statements where this variable is being checked against null
*/
// https://bugs.eclipse.org/bugs/show_bug.cgi?id=303448
abstract public void markedAsNullOrNonNullInAssertExpression(LocalVariableBinding local);
/**
* Returns true if the local variable being checked for was marked as null or not null inside an
* assert expression due to comparison against null.
*/
//https://bugs.eclipse.org/bugs/show_bug.cgi?id=303448
abstract public boolean isMarkedAsNullOrNonNullInAssertExpression(LocalVariableBinding local);
}