Index: cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
===================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
@@ -120,6 +120,7 @@
   void evalStdCopy(CheckerContext &C, const CallExpr *CE) const;
   void evalStdCopyBackward(CheckerContext &C, const CallExpr *CE) const;
   void evalStdCopyCommon(CheckerContext &C, const CallExpr *CE) const;
+  void evalMemset(CheckerContext &C, const CallExpr *CE) const;
 
   // Utility methods
   std::pair<ProgramStateRef , ProgramStateRef >
@@ -1999,6 +2000,54 @@
   C.addTransition(State);
 }
 
+void CStringChecker::evalMemset(CheckerContext &C, const CallExpr *CE) const {
+  if (CE->getNumArgs() != 3)
+    return;
+
+  CurrentFunctionDescription = "memory set function";
+
+  const Expr *Mem = CE->getArg(0);
+  const Expr *Size = CE->getArg(2);
+  ProgramStateRef State = C.getState();
+
+  // See if the size argument is zero.
+  const LocationContext *LCtx = C.getLocationContext();
+  SVal SizeVal = State->getSVal(Size, LCtx);
+  QualType SizeTy = Size->getType();
+
+  ProgramStateRef StateZeroSize, StateNonZeroSize;
+  std::tie(StateZeroSize, StateNonZeroSize) =
+    assumeZero(C, State, SizeVal, SizeTy);
+
+  // Get the value of the memory area.
+  SVal MemVal = State->getSVal(Mem, LCtx);
+
+  // If the size is zero, there won't be any actual memory access, so
+  // just bind the return value to the Mem buffer and return.
+  if (StateZeroSize && !StateNonZeroSize) {
+    StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, MemVal);
+    C.addTransition(StateZeroSize);
+    return;
+  }
+
+  // Ensure the memory area is not null.
+  // If it is NULL there will be a NULL pointer dereference.
+  State = checkNonNull(C, StateNonZeroSize, Mem, MemVal);
+  if (!State)
+    return;
+
+  State = CheckBufferAccess(C, State, Size, Mem);
+  if (!State)
+    return;
+  State = InvalidateBuffer(C, State, Mem, C.getSVal(Mem),
+                           /*IsSourceBuffer*/false, Size);
+  if (!State)
+    return;
+
+  State = State->BindExpr(CE, LCtx, MemVal);
+  C.addTransition(State);
+}
+
 static bool isCPPStdLibraryFunction(const FunctionDecl *FD, StringRef Name) {
   IdentifierInfo *II = FD->getIdentifier();
   if (!II)
@@ -2032,6 +2081,8 @@
     evalFunction =  &CStringChecker::evalMemcmp;
   else if (C.isCLibraryFunction(FDecl, "memmove"))
     evalFunction =  &CStringChecker::evalMemmove;
+  else if (C.isCLibraryFunction(FDecl, "memset"))
+    evalFunction =  &CStringChecker::evalMemset;
   else if (C.isCLibraryFunction(FDecl, "strcpy"))
     evalFunction =  &CStringChecker::evalStrcpy;
   else if (C.isCLibraryFunction(FDecl, "strncpy"))
Index: cfe/trunk/test/Analysis/null-deref-ps-region.c
===================================================================
--- cfe/trunk/test/Analysis/null-deref-ps-region.c
+++ cfe/trunk/test/Analysis/null-deref-ps-region.c
@@ -1,6 +1,11 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core -std=gnu99 -analyzer-store=region -verify %s
-// expected-no-diagnostics
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core,unix,alpha.unix -std=gnu99 -analyzer-store=region -verify %s
 
+#include "Inputs/system-header-simulator.h"
+
+typedef __typeof(sizeof(int)) size_t;
+void *memset(void *__s, int __c, size_t __n);
+void *malloc(size_t __size);
+void free(void *__ptr);
 
 // The store for 'a[1]' should not be removed mistakenly. SymbolicRegions may
 // also be live roots.
@@ -13,3 +18,55 @@
     i = *p; // no-warning
   }
 }
+
+void foo() {
+  int *x = malloc(sizeof(int));
+  memset(x, 0, sizeof(int));
+  int n = 1 / *x; // FIXME: no-warning
+  free(x);
+}
+
+void bar() {
+  int *x = malloc(sizeof(int));
+  memset(x, 0, 1);
+  int n = 1 / *x; // no-warning
+  free(x);
+}
+
+void testConcreteNull() {
+  int *x = 0;
+  memset(x, 0, 1); // expected-warning {{Null pointer argument in call to memory set function}}
+}
+
+void testStackArray() {
+  char buf[13];
+  memset(buf, 0, 1); // no-warning
+}
+
+void testHeapSymbol() {
+  char *buf = (char *)malloc(13);
+  memset(buf, 0, 1); // no-warning
+  free(buf);
+}
+
+void testStackArrayOutOfBound() {
+  char buf[1];
+  memset(buf, 0, 1024); // expected-warning {{Memory set function accesses out-of-bound array element}}
+}
+
+void testHeapSymbolOutOfBound() {
+  char *buf = (char *)malloc(1);
+  memset(buf, 0, 1024); // expected-warning {{Memory set function accesses out-of-bound array element}}
+  free(buf);
+}
+
+void testStackArraySameSize() {
+  char buf[1];
+  memset(buf, 0, sizeof(buf)); // no-warning
+}
+
+void testHeapSymbolSameSize() {
+  char *buf = (char *)malloc(1);
+  memset(buf, 0, 1); // no-warning
+  free(buf);
+}