build/clang-plugin/RecurseGuard.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef RecurseGuard_h__
   6 #define RecurseGuard_h__
   7
   8 #include "Utils.h"
   9
  10 // This class acts as a tracker for avoiding infinite recursion when traversing
  11 // chains in CFGs etc.
  12 //
  13 // Constructing a RecurseGuard sets up a shared backing store which tracks the
  14 // currently observed objects. Whenever recursing, use RecurseGuard.recurse(T)
  15 // to construct another RecurseGuard with the same backing store.
  16 //
  17 // The RecurseGuard object will unregister its object when it is destroyed, and
  18 // has a method `isRepeat()` which will return `true` if the item was already
  19 // seen.
  20 template <typename T> class RecurseGuard {
  21 public:
  22   RecurseGuard(T Thing) : Thing(Thing), Set(new DenseSet<T>()), Repeat(false) {
  23     Set->insert(Thing);
  24   }
  25   RecurseGuard(T Thing, std::shared_ptr<DenseSet<T>> &Set)
  26       : Thing(Thing), Set(Set), Repeat(false) {
  27     Repeat = !Set->insert(Thing).second;
  28   }
  29   RecurseGuard(const RecurseGuard &) = delete;
  30   RecurseGuard(RecurseGuard &&Other)
  31       : Thing(Other.Thing), Set(Other.Set), Repeat(Other.Repeat) {
  32     Other.Repeat = true;
  33   }
  34   ~RecurseGuard() {
  35     if (!Repeat) {
  36       Set->erase(Thing);
  37     }
  38   }
  39
  40   bool isRepeat() { return Repeat; }
  41
  42   T get() { return Thing; }
  43
  44   operator T() { return Thing; }
  45
  46   T operator->() { return Thing; }
  47
  48   RecurseGuard recurse(T NewThing) { return RecurseGuard(NewThing, Set); }
  49
  50 private:
  51   T Thing;
  52   std::shared_ptr<DenseSet<T>> Set;
  53   bool Repeat;
  54 };
  55
  56 #endif // RecurseGuard_h__