diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -268,7 +268,7 @@
 
     /// Try our best to figure out if the call expression is the call of
     /// *the* library function to which this specification applies.
-    bool matchesCall(const CallExpr *CE) const;
+    bool matchesCall(const FunctionDecl *FD) const;
   };
 
   // The same function (as in, function identifier) may have different
@@ -316,7 +316,6 @@
 
 private:
   Optional<Summary> findFunctionSummary(const FunctionDecl *FD,
-                                        const CallExpr *CE,
                                         CheckerContext &C) const;
   Optional<Summary> findFunctionSummary(const CallEvent &Call,
                                         CheckerContext &C) const;
@@ -532,13 +531,13 @@
 }
 
 bool StdLibraryFunctionsChecker::Summary::matchesCall(
-    const CallExpr *CE) const {
+    const FunctionDecl *FD) const {
   // Check number of arguments:
-  if (CE->getNumArgs() != ArgTys.size())
+  if (FD->param_size() != ArgTys.size())
     return false;
 
   // Check return type if relevant:
-  if (!RetTy.isNull() && RetTy != CE->getType().getCanonicalType())
+  if (!RetTy.isNull() && RetTy != FD->getReturnType().getCanonicalType())
     return false;
 
   // Check argument types when relevant:
@@ -550,7 +549,7 @@
 
     assertTypeSuitableForSummary(FormalT);
 
-    QualType ActualT = StdLibraryFunctionsChecker::getArgType(CE, I);
+    QualType ActualT = FD->getParamDecl(I)->getType().getCanonicalType();
     assert(ActualT.isCanonical());
     if (ActualT != FormalT)
       return false;
@@ -561,12 +560,7 @@
 
 Optional<StdLibraryFunctionsChecker::Summary>
 StdLibraryFunctionsChecker::findFunctionSummary(const FunctionDecl *FD,
-                                                const CallExpr *CE,
                                                 CheckerContext &C) const {
-  // Note: we cannot always obtain FD from CE
-  // (eg. virtual call, or call by pointer).
-  assert(CE);
-
   if (!FD)
     return None;
 
@@ -590,7 +584,7 @@
   // return values.
   const Summaries &SpecVariants = FSMI->second;
   for (const Summary &Spec : SpecVariants)
-    if (Spec.matchesCall(CE))
+    if (Spec.matchesCall(FD))
       return Spec;
 
   return None;
@@ -602,10 +596,7 @@
   const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
   if (!FD)
     return None;
-  const CallExpr *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
-  if (!CE)
-    return None;
-  return findFunctionSummary(FD, CE, C);
+  return findFunctionSummary(FD, C);
 }
 
 void StdLibraryFunctionsChecker::initFunctionSummaries(
@@ -630,9 +621,15 @@
   const QualType LongTy = ACtx.LongTy;
   const QualType LongLongTy = ACtx.LongLongTy;
   const QualType SizeTy = ACtx.getSizeType();
-  const QualType VoidPtrTy = ACtx.VoidPtrTy; // void *T
+  const QualType VoidPtrTy = ACtx.VoidPtrTy; // void *
+  const QualType VoidPtrRestrictTy =
+      ACtx.getRestrictType(VoidPtrTy); // void *restrict
   const QualType ConstVoidPtrTy =
-      ACtx.getPointerType(ACtx.VoidTy.withConst()); // const void *T
+      ACtx.getPointerType(ACtx.VoidTy.withConst()); // const void *
+  const QualType ConstCharPtrTy =
+      ACtx.getPointerType(ACtx.CharTy.withConst()); // const char *
+  const QualType ConstVoidPtrRestrictTy =
+      ACtx.getRestrictType(ConstVoidPtrTy); // const void *restrict
 
   const RangeInt IntMax = BVF.getMaxValue(IntTy).getLimitedValue();
   const RangeInt LongMax = BVF.getMaxValue(LongTy).getLimitedValue();
@@ -721,7 +718,7 @@
                ReturnValueCondition(WithinRange, Range(-1, Max))});
   };
   auto Fread = [&]() {
-    return Summary(ArgTypes{VoidPtrTy, Irrelevant, SizeTy, Irrelevant},
+    return Summary(ArgTypes{VoidPtrRestrictTy, Irrelevant, SizeTy, Irrelevant},
                    RetType{SizeTy}, NoEvalCall)
         .Case({
             ReturnValueCondition(LessThanOrEq, ArgNo(2)),
@@ -729,8 +726,9 @@
         .ArgConstraint(NotNull(ArgNo(0)));
   };
   auto Fwrite = [&]() {
-    return Summary(ArgTypes{ConstVoidPtrTy, Irrelevant, SizeTy, Irrelevant},
-                   RetType{SizeTy}, NoEvalCall)
+    return Summary(
+               ArgTypes{ConstVoidPtrRestrictTy, Irrelevant, SizeTy, Irrelevant},
+               RetType{SizeTy}, NoEvalCall)
         .Case({
             ReturnValueCondition(LessThanOrEq, ArgNo(2)),
         })
@@ -960,7 +958,10 @@
                            ArgumentCondition(0U, OutOfRange, SingleValue(1)))
                        .ArgConstraint(
                            ArgumentCondition(0U, OutOfRange, SingleValue(2)))}},
-    };
+        {"__variadic", Summaries{Summary(ArgTypes{VoidPtrTy, ConstCharPtrTy},
+                                         RetType{IntTy}, EvalCallAsPure)
+                                     .ArgConstraint(NotNull(ArgNo(0)))
+                                     .ArgConstraint(NotNull(ArgNo(1)))}}};
     for (auto &E : TestFunctionSummaryMap) {
       auto InsertRes =
           FunctionSummaryMap.insert({std::string(E.getKey()), E.getValue()});
diff --git a/clang/test/Analysis/std-c-library-functions-arg-constraints.c b/clang/test/Analysis/std-c-library-functions-arg-constraints.c
--- a/clang/test/Analysis/std-c-library-functions-arg-constraints.c
+++ b/clang/test/Analysis/std-c-library-functions-arg-constraints.c
@@ -64,7 +64,7 @@
 
 typedef struct FILE FILE;
 typedef typeof(sizeof(int)) size_t;
-size_t fread(void *, size_t, size_t, FILE *);
+size_t fread(void *restrict, size_t, size_t, FILE *);
 void test_notnull_concrete(FILE *fp) {
   fread(0, sizeof(int), 10, fp); // \
   // report-warning{{Function argument constraint is not satisfied}} \
@@ -114,3 +114,11 @@
   // bugpath-note{{Assuming 'x' is < 1}} \
   // bugpath-note{{Left side of '||' is true}}
 }
+
+int __variadic(void *stream, const char *format, ...);
+void test_arg_constraint_on_variadic_fun() {
+  __variadic(0, "%d%d", 1, 2); // \
+  // report-warning{{Function argument constraint is not satisfied}} \
+  // bugpath-warning{{Function argument constraint is not satisfied}} \
+  // bugpath-note{{Function argument constraint is not satisfied}}
+}
diff --git a/clang/test/Analysis/std-c-library-functions.c b/clang/test/Analysis/std-c-library-functions.c
--- a/clang/test/Analysis/std-c-library-functions.c
+++ b/clang/test/Analysis/std-c-library-functions.c
@@ -75,7 +75,7 @@
   }
 }
 
-size_t fread(void *, size_t, size_t, FILE *);
+size_t fread(void *restrict, size_t, size_t, FILE *);
 size_t fwrite(const void *restrict, size_t, size_t, FILE *restrict);
 void test_fread_fwrite(FILE *fp, int *buf) {