[analyzer] Track malloc'd regions stored in structs.

The main blocker on this (besides the previous commit) was that
ScanReachableSymbols was not looking through LazyCompoundVals.
Once that was fixed, it's easy enough to clear out malloc data on return,
just like we do when we bind to a global region.

<rdar://problem/10872635>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161511 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 41 insertions, 43 deletions

diff --git a/lib/StaticAnalyzer/Checkers/MallocChecker.cpp b/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
index 4f19c2ee07..d384bc34f9 100644
--- a/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
@@ -1000,10 +1000,11 @@ void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
   SmallString<200> buf;
   llvm::raw_svector_ostream os(buf);
   os << "Memory is never released; potential leak";
-  if (Region) {
+  // FIXME: Make all region pretty-printing nice enough to show.
+  if (Region && isa<VarRegion>(Region)) {
     os << " of memory pointed to by '";
     Region->dumpPretty(os);
-    os <<'\'';
+    os << '\'';
   }
 
   BugReport *R = new BugReport(*BT_Leak, os.str(), N, LocUsedForUniqueing);
@@ -1117,7 +1118,8 @@ void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
     return;
 
   // Check if we are returning a symbol.
-  SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
+  ProgramStateRef State = C.getState();
+  SVal RetVal = State->getSVal(E, C.getLocationContext());
   SymbolRef Sym = RetVal.getAsSymbol();
   if (!Sym)
     // If we are returning a field of the allocated struct or an array element,
@@ -1128,16 +1130,18 @@ void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
         if (const SymbolicRegion *BMR =
               dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
           Sym = BMR->getSymbol();
-  if (!Sym)
-    return;
 
   // Check if we are returning freed memory.
-  if (checkUseAfterFree(Sym, C, E))
-    return;
+  if (Sym)
+    if (checkUseAfterFree(Sym, C, E))
+      return;
 
-  // If this function body is not inlined, check if the symbol is escaping.
-  if (C.getLocationContext()->getParent() == 0)
-    checkEscape(Sym, E, C);
+  // If this function body is not inlined, stop tracking any returned symbols.
+  if (C.getLocationContext()->getParent() == 0) {
+    State =
+      State->scanReachableSymbols<StopTrackingCallback>(RetVal).getState();
+    C.addTransition(State);
+  }
 }
 
 // TODO: Blocks should be either inlined or should call invalidate regions
@@ -1245,12 +1249,6 @@ void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
       if (StoredVal != val)
         escapes = (state == (state->bindLoc(*regionLoc, val)));
     }
-    if (!escapes) {
-      // Case 4: We do not currently model what happens when a symbol is
-      // assigned to a struct field, so be conservative here and let the symbol
-      // go. TODO: This could definitely be improved upon.
-      escapes = !isa<VarRegion>(regionLoc->getRegion());
-    }
   }
 
   // If our store can represent the binding and we aren't storing to something
diff --git a/lib/StaticAnalyzer/Core/ProgramState.cpp b/lib/StaticAnalyzer/Core/ProgramState.cpp
index 9245a70dd2..c20979bddb 100644
--- a/lib/StaticAnalyzer/Core/ProgramState.cpp
+++ b/lib/StaticAnalyzer/Core/ProgramState.cpp
@@ -542,6 +542,9 @@ bool ScanReachableSymbols::scan(SVal val) {
   if (loc::MemRegionVal *X = dyn_cast<loc::MemRegionVal>(&val))
     return scan(X->getRegion());
 
+  if (nonloc::LazyCompoundVal *X = dyn_cast<nonloc::LazyCompoundVal>(&val))
+    return scan(X->getRegion());
+
   if (nonloc::LocAsInteger *X = dyn_cast<nonloc::LocAsInteger>(&val))
     return scan(X->getLoc());
 
diff --git a/test/Analysis/malloc-annotations.c b/test/Analysis/malloc-annotations.c
index 089e53132d..1dc0f7837b 100644
--- a/test/Analysis/malloc-annotations.c
+++ b/test/Analysis/malloc-annotations.c
@@ -70,10 +70,9 @@ void af1_c() {
   myglobalpointer = my_malloc(12); // no-warning
 }
 
-// TODO: We will be able to handle this after we add support for tracking allocations stored in struct fields.
 void af1_d() {
   struct stuff mystuff;
-  mystuff.somefield = my_malloc(12); // false negative
+  mystuff.somefield = my_malloc(12); // expected-warning{{Memory is never released; potential leak}}
 }
 
 // Test that we can pass out allocated memory via pointer-to-pointer.
diff --git a/test/Analysis/malloc.c b/test/Analysis/malloc.c
index 7f5062af45..24fa30baa8 100644
--- a/test/Analysis/malloc.c
+++ b/test/Analysis/malloc.c
@@ -513,20 +513,20 @@ void testMalloc() {
   int *x = malloc(12);
   StructWithPtr St;
   St.memP = x;
-  arrOfStructs[0] = St;
+  arrOfStructs[0] = St; // no-warning
 }
 
 StructWithPtr testMalloc2() {
   int *x = malloc(12);
   StructWithPtr St;
   St.memP = x;
-  return St;
+  return St; // no-warning
 }
 
 int *testMalloc3() {
   int *x = malloc(12);
   int *y = x;
-  return y;
+  return y; // no-warning
 }
 
 void testElemRegion1() {
@@ -926,31 +926,16 @@ int cmpHeapAllocationToUnknown() {
   return 0;
 }
 
-// ----------------------------------------------------------------------------
-// False negatives.
-
-// TODO: This requires tracking symbols stored inside the structs/arrays.
-void testMalloc5() {
-  StructWithPtr St;
-  StructWithPtr *pSt = &St;
-  pSt->memP = malloc(12);
-}
-
-// TODO: This is another false negative.
-void testMallocWithParam(int **p) {
-  *p = (int*) malloc(sizeof(int));
-  *p = 0;
-}
-
-void testMallocWithParam_2(int **p) {
-  *p = (int*) malloc(sizeof(int));
-}
-
-// TODO: This should produce a warning, similar to the previous issue.
 void localArrayTest() {
   char *p = (char*)malloc(12);
   char *ArrayL[12];
-  ArrayL[0] = p;
+  ArrayL[0] = p; // expected-warning {{leak}}
+}
+
+void localStructTest() {
+  StructWithPtr St;
+  StructWithPtr *pSt = &St;
+  pSt->memP = malloc(12); // expected-warning{{Memory is never released; potential leak}}
 }
 
 // Test double assignment through integers.
@@ -1019,3 +1004,16 @@ int* reallocButNoMalloc(struct HasPtr *a, int c, int size) {
     return 0; // expected-warning{{Memory is never released; potential leak}}
   return a->p;
 }
+
+// ----------------------------------------------------------------------------
+// False negatives.
+
+// TODO: This is another false negative.
+void testMallocWithParam(int **p) {
+  *p = (int*) malloc(sizeof(int));
+  *p = 0;
+}
+
+void testMallocWithParam_2(int **p) {
+  *p = (int*) malloc(sizeof(int));
+}