C#: Make CFG library shared

Author: hvitved

csharp/ql/lib/semmle/code/csharp/Caching.qll

@@ -18,7 +18,7 @@ module Stages {
 
     cached
     private predicate forceCachingInSameStageRev() {
-      exists(SplitImpl si)
+      exists(Split s)
       or
       exists(SuccessorType st)
       or

csharp/ql/lib/semmle/code/csharp/controlflow/ControlFlowGraph.qll

@@ -183,7 +183,7 @@ module ControlFlow {
     }
 
     /** Gets a successor node of a given type, if any. */
-    Node getASuccessorByType(SuccessorType t) { result = getASuccessorByType(this, t) }
+    Node getASuccessorByType(SuccessorType t) { result = getASuccessor(this, t) }
 
     /** Gets an immediate successor, if any. */
     Node getASuccessor() { result = getASuccessorByType(_) }
@@ -255,9 +255,15 @@ module ControlFlow {
 
       override Callable getEnclosingCallable() { result = this.getCallable() }
 
-      override Location getLocation() { result = getCallable().getLocation() }
+      private Assignable getAssignable() { this = TEntryNode(result) }
+
+      override Location getLocation() {
+        result in [this.getCallable().getLocation(), this.getAssignable().getLocation()]
+      }
 
-      override string toString() { result = "enter " + getCallable().toString() }
+      override string toString() {
+        result = "enter " + [this.getCallable().toString(), this.getAssignable().toString()]
+      }
     }
 
     /** A node for a callable exit point, annotated with the type of exit. */
@@ -314,7 +320,7 @@ module ControlFlow {
      * different splits for the element.
      */
     class ElementNode extends Node, TElementNode {
-      private Splitting::Splits splits;
+      private Splits splits;
       private ControlFlowElement cfe;
 
       ElementNode() { this = TElementNode(cfe, splits) }

csharp/ql/lib/semmle/code/csharp/controlflow/internal/ControlFlowGraphImpl.qll

@@ -43,13 +43,22 @@
  */
 
 import csharp
-private import semmle.code.csharp.controlflow.ControlFlowGraph::ControlFlow
 private import Completion
-private import SuccessorType
-private import SuccessorTypes
 private import Splitting
 private import semmle.code.csharp.ExprOrStmtParent
 private import semmle.code.csharp.commons.Compilation
+import ControlFlowGraphImplShared
+
+/** An element that defines a new CFG scope. */
+class CfgScope extends Element, @top_level_exprorstmt_parent {
+  CfgScope() {
+    this instanceof Callable
+    or
+    // For now, static initializer values have their own scope. Eventually, they
+    // should be treated like instance initializers.
+    this.(Assignable).(Modifiable).isStatic()
+  }
+}
 
 /**
  * A compilation.
@@ -71,16 +80,11 @@ CompilationExt getCompilation(SourceFile f) {
   result = TBuildless()
 }
 
-/** An element that defines a new CFG scope. */
-class CfgScope extends Element, @top_level_exprorstmt_parent {
-  CfgScope() { not this instanceof Attribute }
-}
-
 module ControlFlowTree {
   class Range_ = @callable or @control_flow_element;
 
   class Range extends Element, Range_ {
-    Range() { this = getAChild*(any(CfgScope scope)) }
+    Range() { this = getAChild*(any(@top_level_exprorstmt_parent p | not p instanceof Attribute)) }
   }
 
   Element getAChild(Element p) {
@@ -93,61 +97,6 @@ module ControlFlowTree {
   predicate idOf(Range_ x, int y) = equivalenceRelation(id/2)(x, y)
 }
 
-abstract private class ControlFlowTree extends ControlFlowTree::Range {
-  /**
-   * Holds if `first` is the first element executed within this control
-   * flow element.
-   */
-  pragma[nomagic]
-  abstract predicate first(ControlFlowElement first);
-
-  /**
-   * Holds if `last` with completion `c` is a potential last element executed
-   * within this control flow element.
-   */
-  pragma[nomagic]
-  abstract predicate last(ControlFlowElement last, Completion c);
-
-  /** Holds if abnormal execution of `child` should propagate upwards. */
-  abstract predicate propagatesAbnormal(ControlFlowElement child);
-
-  /**
-   * Holds if `succ` is a control flow successor for `pred`, given that `pred`
-   * finishes with completion `c`.
-   */
-  pragma[nomagic]
-  abstract predicate succ(ControlFlowElement pred, ControlFlowElement succ, Completion c);
-}
-
-/**
- * Holds if `first` is the first element executed within control flow
- * element `cft`.
- */
-predicate first(ControlFlowTree cft, ControlFlowElement first) { cft.first(first) }
-
-/**
- * Holds if `last` with completion `c` is a potential last element executed
- * within control flow element `cft`.
- */
-predicate last(ControlFlowTree cft, ControlFlowElement last, Completion c) {
-  cft.last(last, c)
-  or
-  exists(ControlFlowElement cfe |
-    cft.propagatesAbnormal(cfe) and
-    last(cfe, last, c) and
-    not c instanceof NormalCompletion
-  )
-}
-
-/**
- * Holds if `succ` is a control flow successor for `pred`, given that `pred`
- * finishes with completion `c`.
- */
-pragma[nomagic]
-predicate succ(ControlFlowElement pred, ControlFlowElement succ, Completion c) {
-  any(ControlFlowTree cft).succ(pred, succ, c)
-}
-
 /** Holds if `first` is first executed when entering `scope`. */
 predicate scopeFirst(CfgScope scope, ControlFlowElement first) {
   scope =
@@ -161,8 +110,7 @@ predicate scopeFirst(CfgScope scope, ControlFlowElement first) {
     )
   or
   expr_parent_top_level_adjusted(any(Expr e | first(e, first)), _, scope) and
-  not scope instanceof Callable and
-  not scope instanceof InitializerSplitting::InitializedInstanceMember
+  not scope instanceof Callable
 }
 
 /** Holds if `scope` is exited when `last` finishes with completion `c`. */
@@ -204,53 +152,6 @@ private class ConstructorTree extends ControlFlowTree, Constructor {
   }
 }
 
-/**
- * A control flow element where the children are evaluated following a
- * standard left-to-right evaluation. The actual evaluation order is
- * determined by the predicate `getChildElement()`.
- */
-abstract private class StandardElement extends ControlFlowTree {
-  /** Gets the `i`th child element, in order of evaluation, starting from 0. */
-  abstract ControlFlowElement getChildElement(int i);
-
-  /** Gets the first child element of this element. */
-  final ControlFlowElement getFirstChild() { result = this.getChildElement(0) }
-
-  /** Holds if this element has no children. */
-  final predicate isLeafElement() { not exists(this.getFirstChild()) }
-
-  /** Gets the last child element of this element. */
-  final ControlFlowTree getLastChild() {
-    exists(int last |
-      result = this.getChildElement(last) and
-      not exists(this.getChildElement(last + 1))
-    )
-  }
-
-  final override predicate propagatesAbnormal(ControlFlowElement child) {
-    child = this.getChildElement(_)
-  }
-
-  override predicate succ(ControlFlowElement pred, ControlFlowElement succ, Completion c) {
-    exists(int i |
-      last(this.getChildElement(i), pred, c) and
-      first(this.getChildElement(i + 1), succ) and
-      c instanceof NormalCompletion
-    )
-  }
-}
-
-abstract private class PreOrderTree extends ControlFlowTree {
-  final override predicate first(ControlFlowElement first) { first = this }
-}
-
-abstract private class PostOrderTree extends ControlFlowTree {
-  override predicate last(ControlFlowElement last, Completion c) {
-    last = this and
-    c.isValidFor(last)
-  }
-}
-
 abstract private class SwitchTree extends ControlFlowTree, Switch {
   override predicate propagatesAbnormal(ControlFlowElement child) { child = this.getExpr() }
 
@@ -368,7 +269,7 @@ module Expressions {
     )
   }
 
-  private class StandardExpr extends StandardElement, PostOrderTree, Expr {
+  private class StandardExpr extends StandardPostOrderTree, Expr {
     StandardExpr() {
       // The following expressions need special treatment
       not this instanceof LogicalNotExpr and
@@ -396,21 +297,6 @@ module Expressions {
     }
 
     final override ControlFlowElement getChildElement(int i) { result = getExprChild(this, i) }
-
-    final override predicate first(ControlFlowElement first) {
-      first(this.getFirstChild(), first)
-      or
-      not exists(this.getFirstChild()) and
-      first = this
-    }
-
-    final override predicate succ(ControlFlowElement pred, ControlFlowElement succ, Completion c) {
-      StandardElement.super.succ(pred, succ, c)
-      or
-      last(this.getLastChild(), pred, c) and
-      succ = this and
-      c instanceof NormalCompletion
-    }
   }
 
   /**
@@ -1095,7 +981,7 @@ private class PropertyPatternExprExprTree extends PostOrderTree, PropertyPattern
 }
 
 module Statements {
-  private class StandardStmt extends StandardElement, PreOrderTree, Stmt {
+  private class StandardStmt extends StandardPreOrderTree, Stmt {
     StandardStmt() {
       // The following statements need special treatment
       not this instanceof IfStmt and
@@ -1140,22 +1026,6 @@ module Statements {
       result =
         rank[i + 1](ControlFlowElement cfe, int j | cfe = this.getChildElement0(j) | cfe order by j)
     }
-
-    final override predicate last(ControlFlowElement last, Completion c) {
-      last(this.getLastChild(), last, c)
-      or
-      this.isLeafElement() and
-      last = this and
-      c.isValidFor(this)
-    }
-
-    final override predicate succ(ControlFlowElement pred, ControlFlowElement succ, Completion c) {
-      StandardElement.super.succ(pred, succ, c)
-      or
-      pred = this and
-      first(this.getFirstChild(), succ) and
-      c instanceof SimpleCompletion
-    }
   }
 
   private class IfStmtTree extends PreOrderTree, IfStmt {
@@ -1779,88 +1649,6 @@ module Statements {
   }
 }
 
-cached
-private module Cached {
-  private import semmle.code.csharp.Caching
-
-  private predicate isAbnormalExitType(SuccessorType t) {
-    t instanceof ExceptionSuccessor or t instanceof ExitSuccessor
-  }
-
-  /**
-   * Internal representation of control flow nodes in the control flow graph.
-   * The control flow graph is pruned for unreachable nodes.
-   */
-  cached
-  newtype TNode =
-    TEntryNode(Callable c) {
-      Stages::ControlFlowStage::forceCachingInSameStage() and
-      succEntrySplits(c, _, _, _)
-    } or
-    TAnnotatedExitNode(Callable c, boolean normal) {
-      exists(Reachability::SameSplitsBlock b, SuccessorType t | b.isReachable(_) |
-        succExitSplits(b.getAnElement(), _, c, t) and
-        if isAbnormalExitType(t) then normal = false else normal = true
-      )
-    } or
-    TExitNode(Callable c) {
-      exists(Reachability::SameSplitsBlock b | b.isReachable(_) |
-        succExitSplits(b.getAnElement(), _, c, _)
-      )
-    } or
-    TElementNode(ControlFlowElement cfe, Splits splits) {
-      exists(Reachability::SameSplitsBlock b | b.isReachable(splits) | cfe = b.getAnElement())
-    }
-
-  /** Gets a successor node of a given flow type, if any. */
-  cached
-  Node getASuccessorByType(Node pred, SuccessorType t) {
-    // Callable entry node -> callable body
-    exists(ControlFlowElement succElement, Splits succSplits |
-      result = TElementNode(succElement, succSplits)
-    |
-      succEntrySplits(pred.(Nodes::EntryNode).getCallable(), succElement, succSplits, t)
-    )
-    or
-    exists(ControlFlowElement predElement, Splits predSplits |
-      pred = TElementNode(predElement, predSplits)
-    |
-      // Element node -> callable exit (annotated)
-      result =
-        any(Nodes::AnnotatedExitNode exit |
-          succExitSplits(predElement, predSplits, exit.getCallable(), t) and
-          if isAbnormalExitType(t) then not exit.isNormal() else exit.isNormal()
-        )
-      or
-      // Element node -> element node
-      exists(ControlFlowElement succElement, Splits succSplits, Completion c |
-        result = TElementNode(succElement, succSplits)
-      |
-        succSplits(predElement, predSplits, succElement, succSplits, c) and
-        t = c.getAMatchingSuccessorType()
-      )
-    )
-    or
-    // Callable exit (annotated) -> callable exit
-    pred.(Nodes::AnnotatedExitNode).getCallable() = result.(Nodes::ExitNode).getCallable() and
-    t instanceof SuccessorTypes::NormalSuccessor
-  }
-
-  /**
-   * Gets a first control flow element executed within `cfe`.
-   */
-  cached
-  ControlFlowElement getAControlFlowEntryNode(ControlFlowElement cfe) { first(cfe, result) }
-
-  /**
-   * Gets a potential last control flow element executed within `cfe`.
-   */
-  cached
-  ControlFlowElement getAControlFlowExitNode(ControlFlowElement cfe) { last(cfe, result, _) }
-}
-
-import Cached
-
 /** A control flow element that is split into multiple control flow nodes. */
 class SplitControlFlowElement extends ControlFlowElement {
   SplitControlFlowElement() { strictcount(this.getAControlFlowNode()) > 1 }