[PATCH] D66131: [analyzer] Don't track the condition of foreach loops

[Kristóf Umann via Phabricator via cfe-commits]

Szelethus created this revision.
Szelethus added reviewers: NoQ, xazax.hun, baloghadamsoftware, dcoughlin, rnkovacs, Charusso.
Szelethus added a project: clang.
Herald added subscribers: cfe-commits, gamesh411, dkrupp, donat.nagy, mikhail.ramalho, a.sidorin, szepet, whisperity.

As discussed on the mailing list, notes originating from the tracking of foreach loop conditions are always meaningless.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D66131

Files:
  clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
  clang/test/Analysis/track-control-dependency-conditions.cpp


Index: clang/test/Analysis/track-control-dependency-conditions.cpp
===================================================================
--- clang/test/Analysis/track-control-dependency-conditions.cpp
+++ clang/test/Analysis/track-control-dependency-conditions.cpp
@@ -407,6 +407,40 @@
 }
 } // end of namespace condition_written_in_nested_stackframe_before_assignment
 
+namespace dont_explain_foreach_loops {
+
+struct Iterator {
+  int *pos;
+  bool operator!=(Iterator other) const {
+    return pos && other.pos && pos != other.pos;
+  }
+  int operator*();
+  Iterator operator++();
+};
+
+struct Container {
+  Iterator begin();
+  Iterator end();
+};
+
+void f(Container Cont) {
+  int flag = 0;
+  int *x = 0; // expected-note{{'x' initialized to a null pointer value}}
+  for (int i : Cont)
+    if (i) // expected-note   {{Assuming 'i' is not equal to 0}}
+           // expected-note at -1{{Taking true branch}}
+           // debug-note at -2{{Tracking condition 'i'}}
+      flag = i;
+
+  if (flag) // expected-note{{'flag' is not equal to 0}}
+            // expected-note at -1{{Taking true branch}}
+            // debug-note at -2{{Tracking condition 'flag'}}
+    *x = 5; // expected-warning{{Dereference of null pointer}}
+            // expected-note at -1{{Dereference of null pointer}}
+}
+
+} // end of namespace dont_explain_foreach_loops
+
 namespace collapse_point_not_in_condition_bool {
 
 [[noreturn]] void halt();
Index: clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
+++ clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
@@ -1830,6 +1830,11 @@
     return nullptr;
 
   if (ControlDeps.isControlDependent(OriginB, NB)) {
+    // We don't really want to explain for range loops. Evidence suggests that
+    // the only thing that leads to is the addition of calls to operator!=.
+    if (isa<CXXForRangeStmt>(NB->getTerminator()))
+      return nullptr;
+
     if (const Expr *Condition = NB->getLastCondition()) {
       // Keeping track of the already tracked conditions on a visitor level
       // isn't sufficient, because a new visitor is created for each tracked


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