[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)

llvm-svn: 147569

1 files changed, 6 insertions, 4 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
index 4134b352bed..99752e5408d 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
@@ -294,15 +294,17 @@ void ExprEngine::VisitCXXNewExpr(const CXXNewExpr *CNE, ExplodedNode *Pred,
     if (ObjTy->isRecordType()) {
       regionsToInvalidate.push_back(EleReg);
       // Invalidate the regions.
+      // TODO: Pass the call to new information as the last argument, to limit
+      // the globals which will get invalidated.
       state = state->invalidateRegions(regionsToInvalidate,
-                                       CNE, blockCount, 0,
-                                       /* invalidateGlobals = */ true);
+                                       CNE, blockCount, 0, 0);
       
     } else {
       // Invalidate the regions.
+      // TODO: Pass the call to new information as the last argument, to limit
+      // the globals which will get invalidated.
       state = state->invalidateRegions(regionsToInvalidate,
-                                       CNE, blockCount, 0,
-                                       /* invalidateGlobals = */ true);
+                                       CNE, blockCount, 0, 0);
 
       if (CNE->hasInitializer()) {
         SVal V = state->getSVal(*CNE->constructor_arg_begin());