r356049 - [Analyzer] Skip symbolic regions based on conjured symbols in comparison of the containers of iterators

[Adam Balogh via cfe-commits]

Author: baloghadamsoftware
Date: Wed Mar 13 06:55:11 2019
New Revision: 356049

URL: http://llvm.org/viewvc/llvm-project?rev=356049&view=rev
Log:
[Analyzer] Skip symbolic regions based on conjured symbols in comparison of the containers of iterators

Checking whether two regions are the same is a partially decidable problem:
either we know for sure that they are the same or we cannot decide. A typical
case for this are the symbolic regions based on conjured symbols. Two
different conjured symbols are either the same or they are different. Since
we cannot decide this and want to reduce false positives as much as possible
we exclude these regions whenever checking whether two containers are the
same at iterator mismatch check.

Differential Revision: https://reviews.llvm.org/D53754


Modified:
    cfe/trunk/lib/StaticAnalyzer/Checkers/IteratorChecker.cpp
    cfe/trunk/test/Analysis/mismatched-iterator.cpp

Modified: cfe/trunk/lib/StaticAnalyzer/Checkers/IteratorChecker.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/IteratorChecker.cpp?rev=356049&r1=356048&r2=356049&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/IteratorChecker.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/IteratorChecker.cpp Wed Mar 13 06:55:11 2019
@@ -1098,14 +1098,34 @@ void IteratorChecker::verifyMatch(Checke
   // Verify match between a container and the container of an iterator
   Cont = Cont->getMostDerivedObjectRegion();
 
+  if (const auto *ContSym = Cont->getSymbolicBase()) {
+    if (isa<SymbolConjured>(ContSym->getSymbol()))
+      return;
+  }
+
   auto State = C.getState();
   const auto *Pos = getIteratorPosition(State, Iter);
-  if (Pos && Pos->getContainer() != Cont) {
+  if (!Pos)
+    return;
+
+  const auto *IterCont = Pos->getContainer();
+
+  // Skip symbolic regions based on conjured symbols. Two conjured symbols
+  // may or may not be the same. For example, the same function can return
+  // the same or a different container but we get different conjured symbols
+  // for each call. This may cause false positives so omit them from the check.
+  if (const auto *ContSym = IterCont->getSymbolicBase()) {
+    if (isa<SymbolConjured>(ContSym->getSymbol()))
+      return;
+  }
+
+  if (IterCont != Cont) {
     auto *N = C.generateNonFatalErrorNode(State);
     if (!N) {
       return;
     }
-    reportMismatchedBug("Container accessed using foreign iterator argument.", Iter, Cont, C, N);
+    reportMismatchedBug("Container accessed using foreign iterator argument.",
+                        Iter, Cont, C, N);
   }
 }
 
@@ -1114,8 +1134,31 @@ void IteratorChecker::verifyMatch(Checke
   // Verify match between the containers of two iterators
   auto State = C.getState();
   const auto *Pos1 = getIteratorPosition(State, Iter1);
+  if (!Pos1)
+    return;
+
+  const auto *IterCont1 = Pos1->getContainer();
+
+  // Skip symbolic regions based on conjured symbols. Two conjured symbols
+  // may or may not be the same. For example, the same function can return
+  // the same or a different container but we get different conjured symbols
+  // for each call. This may cause false positives so omit them from the check.
+  if (const auto *ContSym = IterCont1->getSymbolicBase()) {
+    if (isa<SymbolConjured>(ContSym->getSymbol()))
+      return;
+  }
+
   const auto *Pos2 = getIteratorPosition(State, Iter2);
-  if (Pos1 && Pos2 && Pos1->getContainer() != Pos2->getContainer()) {
+  if (!Pos2)
+    return;
+
+  const auto *IterCont2 = Pos2->getContainer();
+  if (const auto *ContSym = IterCont2->getSymbolicBase()) {
+    if (isa<SymbolConjured>(ContSym->getSymbol()))
+      return;
+  }
+
+  if (IterCont1 != IterCont2) {
     auto *N = C.generateNonFatalErrorNode(State);
     if (!N)
       return;

Modified: cfe/trunk/test/Analysis/mismatched-iterator.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/mismatched-iterator.cpp?rev=356049&r1=356048&r2=356049&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/mismatched-iterator.cpp (original)
+++ cfe/trunk/test/Analysis/mismatched-iterator.cpp Wed Mar 13 06:55:11 2019
@@ -189,3 +189,17 @@ void bad_comparison(std::vector<int> &v1
     *v1.cbegin();
   }
 }
+
+std::vector<int> &return_vector_ref();
+
+void ignore_conjured1() {
+  std::vector<int> &v1 = return_vector_ref(), &v2 = return_vector_ref();
+
+  v2.erase(v1.cbegin()); // no-warning
+}
+
+void ignore_conjured2() {
+  std::vector<int> &v1 = return_vector_ref(), &v2 = return_vector_ref();
+
+  if (v1.cbegin() == v2.cbegin()) {} //no-warning
+}