Index: lib/StaticAnalyzer/Checkers/CStringChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/CStringChecker.cpp
+++ 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 +2000,63 @@
   C.addTransition(State);
 }
 
+void CStringChecker::evalMemset(CheckerContext &C, const CallExpr *CE) const {
+  if (CE->getNumArgs() < 3)
+    return;
+
+  CurrentFunctionDescription = "memory set function";
+
+  const Expr *S = 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 pointed to by S.
+  SVal sVal = state->getSVal(S, LCtx);
+
+  // If the size is zero, there won't be any actual memory access, so           
+  // just bind the return value to the destination buffer and return.
+  if (stateZeroSize && !stateNonZeroSize) {
+    stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, sVal);
+    C.addTransition(stateZeroSize);
+    return;
+  }
+
+  // If the size can be nonzero, we have to check the other arguments.
+  if (stateNonZeroSize) {
+    state = stateNonZeroSize;
+
+    // Ensure the memory area pointed to by s is not null. 
+    // If it is NULL there will be a NULL pointer dereference.
+    state = checkNonNull(C, state, S, sVal);
+    if (!state)
+      return;
+
+    // Ensure the accesses are valid.
+    state = CheckBufferAccess(C, state, Size, S);
+    if (!state)
+      return;
+
+    // Return the memory area pointed to by s buffer.
+    state = state->BindExpr(CE, LCtx, sVal);
+
+    // Invalidate the memory area pointed to by s (regular invalidation without 
+    // pointer-escaping the address of the top-level region). 
+    state = InvalidateBuffer(C, state, S, C.getSVal(S),
+                             /*IsSourceBuffer*/false, Size);
+
+    C.addTransition(state);
+  }
+}
+
 static bool isCPPStdLibraryFunction(const FunctionDecl *FD, StringRef Name) {
   IdentifierInfo *II = FD->getIdentifier();
   if (!II)
@@ -2032,6 +2090,8 @@
     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: test/Analysis/null-deref-ps-region.c
===================================================================
--- test/Analysis/null-deref-ps-region.c
+++ test/Analysis/null-deref-ps-region.c
@@ -1,6 +1,9 @@
-// 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);
 
 // The store for 'a[1]' should not be removed mistakenly. SymbolicRegions may
 // also be live roots.
@@ -13,3 +16,18 @@
     i = *p; // no-warning
   }
 }
+
+void f531() {
+  int *x = 0;
+  memset(x, 0, 1); // expected-warning {{Null pointer argument in call to memory set function}}
+}
+
+void f66() {
+  char buf[1];
+  memset(buf, 0, 1024); // expected-warning {{Memory set function accesses out-of-bound array element}}
+}
+
+void f77() {
+  char buf[1];
+  memset(buf, 0, sizeof(buf)); // no-warning
+}