[analyzer] Add support for testing the presence of weak functions.

When casting the address of a FunctionTextRegion to bool, or when adding
constraints to such an address, use a stand-in symbol to represent the
presence or absence of the function if the function is weakly linked.
This is groundwork for possible simple availability testing checks, and
can already catch mistakes involving inverted null checks for
weakly-linked functions.

Currently, the implementation reuses the "extent" symbols, originally created
for tracking the size of a malloc region. Since FunctionTextRegions cannot
be dereferenced, the extent symbol will never be used for anything else.
Still, this probably deserves a refactoring in the future.

This patch does not attempt to support testing the presence of weak
/variables/ (global variables), which would likely require much more of
a change and a generalization of "region structure metadata", like the
current "extents", vs. "region contents metadata", like CStringChecker's
"string length".

Patch by Richard <tarka.t.otter@googlemail.com>!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189492 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 45 deletions

diff --git a/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp b/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
index a06268dd33..e6653ae6e4 100644
--- a/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
+++ b/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
@@ -68,51 +68,20 @@ bool SimpleConstraintManager::canReasonAbout(SVal X) const {
 ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state,
                                                DefinedSVal Cond,
                                                bool Assumption) {
-  if (Optional<NonLoc> NV = Cond.getAs<NonLoc>())
-    return assume(state, *NV, Assumption);
-  return assume(state, Cond.castAs<Loc>(), Assumption);
-}
-
-ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state, Loc cond,
-                                               bool assumption) {
-  state = assumeAux(state, cond, assumption);
-  if (NotifyAssumeClients && SU)
-    return SU->processAssume(state, cond, assumption);
-  return state;
-}
-
-ProgramStateRef SimpleConstraintManager::assumeAux(ProgramStateRef state,
-                                                  Loc Cond, bool Assumption) {
-  switch (Cond.getSubKind()) {
-  default:
-    assert (false && "'Assume' not implemented for this Loc.");
-    return state;
-
-  case loc::MemRegionKind: {
-    // FIXME: Should this go into the storemanager?
-    const MemRegion *R = Cond.castAs<loc::MemRegionVal>().getRegion();
-
-    // FIXME: now we only find the first symbolic region.
-    if (const SymbolicRegion *SymR = R->getSymbolicBase()) {
-      const llvm::APSInt &zero = getBasicVals().getZeroWithPtrWidth();
-      if (Assumption)
-        return assumeSymNE(state, SymR->getSymbol(), zero, zero);
-      else
-        return assumeSymEQ(state, SymR->getSymbol(), zero, zero);
-    }
-
-    // FALL-THROUGH.
+  // If we have a Loc value, cast it to a bool NonLoc first.
+  if (Optional<Loc> LV = Cond.getAs<Loc>()) {
+    SValBuilder &SVB = state->getStateManager().getSValBuilder();
+    QualType T;
+    const MemRegion *MR = LV->getAsRegion();
+    if (const TypedRegion *TR = dyn_cast_or_null<TypedRegion>(MR))
+      T = TR->getLocationType();
+    else
+      T = SVB.getContext().VoidPtrTy;
+
+    Cond = SVB.evalCast(*LV, SVB.getContext().BoolTy, T).castAs<DefinedSVal>();
   }
 
-  case loc::GotoLabelKind:
-    return Assumption ? state : NULL;
-
-  case loc::ConcreteIntKind: {
-    bool b = Cond.castAs<loc::ConcreteInt>().getValue() != 0;
-    bool isFeasible = b ? Assumption : !Assumption;
-    return isFeasible ? state : NULL;
-  }
-  } // end switch
+  return assume(state, Cond.castAs<NonLoc>(), Assumption);
 }
 
 ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state,
@@ -216,8 +185,8 @@ ProgramStateRef SimpleConstraintManager::assumeAux(ProgramStateRef state,
   }
 
   case nonloc::LocAsIntegerKind:
-    return assumeAux(state, Cond.castAs<nonloc::LocAsInteger>().getLoc(),
-                     Assumption);
+    return assume(state, Cond.castAs<nonloc::LocAsInteger>().getLoc(),
+                  Assumption);
   } // end switch
 }