[analyzer] Protect against dereferencing a null pointer

The check (inside StackHintGeneratorForSymbol::getMessage)
if (!N)
    return getMessageForSymbolNotFound()
is moved to the beginning of the function.

Differential revision: https://reviews.llvm.org/D42388

Test plan: make check-all

llvm-svn: 323146

1 files changed, 3 insertions, 3 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/PathDiagnostic.cpp b/clang/lib/StaticAnalyzer/Core/PathDiagnostic.cpp
index b03517c02a8..fd3de613840 100644
--- a/clang/lib/StaticAnalyzer/Core/PathDiagnostic.cpp
+++ b/clang/lib/StaticAnalyzer/Core/PathDiagnostic.cpp
@@ -1185,6 +1185,9 @@ void PathDiagnostic::FullProfile(llvm::FoldingSetNodeID &ID) const {
 StackHintGenerator::~StackHintGenerator() {}
 
 std::string StackHintGeneratorForSymbol::getMessage(const ExplodedNode *N){
+  if (!N)
+    return getMessageForSymbolNotFound();
+
   ProgramPoint P = N->getLocation();
   CallExitEnd CExit = P.castAs<CallExitEnd>();
 
@@ -1194,9 +1197,6 @@ std::string StackHintGeneratorForSymbol::getMessage(const ExplodedNode *N){
   if (!CE)
     return "";
 
-  if (!N)
-    return getMessageForSymbolNotFound();
-
   // Check if one of the parameters are set to the interesting symbol.
   unsigned ArgIndex = 0;
   for (CallExpr::const_arg_iterator I = CE->arg_begin(),