[analyzer] Be less pessimistic about invalidation of global variables

as a result of a call.

Problem:
Global variables, which come in from system libraries should not be
invalidated by all calls. Also, non-system globals should not be
invalidated by system calls.

Solution:
The following solution to invalidation of globals seems flexible enough
for taint (does not invalidate stdin) and should not lead to too
many false positives. We split globals into 3 classes:

* immutable - values are preserved by calls (unless the specific
global is passed in as a parameter):
     A :  Most system globals and const scalars

* invalidated by functions defined in system headers:
     B: errno

* invalidated by all other functions (note, these functions may in
turn contain system calls):
     B: errno
     C: all other globals (which are not in A nor B)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147569 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 8 deletions

diff --git a/lib/StaticAnalyzer/Checkers/MallocChecker.cpp b/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
index 3c7c907a60..dcc7ab95dc 100644
--- a/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
@@ -407,8 +407,7 @@ bool MallocChecker::SummarizeRegion(raw_ostream &os,
   default: {
     const MemSpaceRegion *MS = MR->getMemorySpace();
     
-    switch (MS->getKind()) {
-    case MemRegion::StackLocalsSpaceRegionKind: {
+    if (isa<StackLocalsSpaceRegion>(MS)) {
       const VarRegion *VR = dyn_cast<VarRegion>(MR);
       const VarDecl *VD;
       if (VR)
@@ -422,7 +421,8 @@ bool MallocChecker::SummarizeRegion(raw_ostream &os,
         os << "the address of a local stack variable";
       return true;
     }
-    case MemRegion::StackArgumentsSpaceRegionKind: {
+
+    if (isa<StackArgumentsSpaceRegion>(MS)) {
       const VarRegion *VR = dyn_cast<VarRegion>(MR);
       const VarDecl *VD;
       if (VR)
@@ -436,8 +436,8 @@ bool MallocChecker::SummarizeRegion(raw_ostream &os,
         os << "the address of a parameter";
       return true;
     }
-    case MemRegion::NonStaticGlobalSpaceRegionKind:
-    case MemRegion::StaticGlobalSpaceRegionKind: {
+
+    if (isa<GlobalsSpaceRegion>(MS)) {
       const VarRegion *VR = dyn_cast<VarRegion>(MR);
       const VarDecl *VD;
       if (VR)
@@ -454,9 +454,8 @@ bool MallocChecker::SummarizeRegion(raw_ostream &os,
         os << "the address of a global variable";
       return true;
     }
-    default:
-      return false;
-    }
+
+    return false;
   }
   }
 }