Index: docs/ReleaseNotes.rst
===================================================================
--- docs/ReleaseNotes.rst
+++ docs/ReleaseNotes.rst
@@ -57,6 +57,8 @@
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+- Add ``-Wincomplete-array-initializer-list`` warning to detect missing
+  elements in initializer lists assigned to array types.
 
 Non-comprehensive list of changes in this release
 -------------------------------------------------
Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -732,6 +732,7 @@
 def Uninitialized  : DiagGroup<"uninitialized", [UninitializedSometimes,
                                                  UninitializedStaticSelfInit,
                                                  UninitializedConstReference]>;
+def IncompleteArrayInitializerList : DiagGroup<"incomplete-array-initializer-list">;
 def IgnoredPragmaIntrinsic : DiagGroup<"ignored-pragma-intrinsic">;
 // #pragma optimize is often used to avoid to work around MSVC codegen bugs or
 // to disable inlining. It's not completely clear what alternative to suggest
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2213,6 +2213,9 @@
   "reference %0 is not yet bound to a value when used within its own"
   " initialization">,
   InGroup<Uninitialized>;
+def warn_incomplete_array_initializer_list : Warning<
+  "incomplete array initializer list">,
+  InGroup<IncompleteArrayInitializerList>, DefaultIgnore;
 def warn_uninit_var : Warning<
   "variable %0 is uninitialized when %select{used here|captured by block}1">,
   InGroup<Uninitialized>, DefaultIgnore;
Index: lib/Sema/SemaInit.cpp
===================================================================
--- lib/Sema/SemaInit.cpp
+++ lib/Sema/SemaInit.cpp
@@ -980,6 +980,21 @@
     if (RequiresSecondPass && !hadError)
       FillInEmptyInitializations(Entity, FullyStructuredList,
                                  RequiresSecondPass, nullptr, 0);
+
+    if (T->isArrayType() && VerifyOnly) {
+      const auto *CAType = dyn_cast<ConstantArrayType>(T);
+      if (CAType && FullyStructuredList->getNumInits() <
+                        CAType->getSize().getZExtValue()) {
+        S.Diag(IL->getBeginLoc(), diag::warn_incomplete_array_initializer_list)
+            << IL->getSourceRange();
+      } else {
+        auto inits = FullyStructuredList->inits();
+        if (llvm::find(inits, nullptr) != inits.end())
+          S.Diag(IL->getBeginLoc(),
+                 diag::warn_incomplete_array_initializer_list)
+              << IL->getSourceRange();
+      }
+    }
   }
   if (hadError && FullyStructuredList)
     FullyStructuredList->markError();
Index: test/Sema/warn-incomplete-initializer-list.c
===================================================================
--- /dev/null
+++ test/Sema/warn-incomplete-initializer-list.c
@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -fsyntax-only -Wincomplete-initializer-list -verify -std=c99 %s
+
+// missing array initializer in between
+enum {
+	FOO1_A,
+	FOO1_MISSING,
+	FOO1_B,
+	FOO1_COUNT
+};
+const char *foo1[] = { // expected-warning{{incomplete initializer list}}
+	[FOO1_A] = "a",
+	[FOO1_B] = "b",
+};
+
+// missing array initializer at end
+enum {
+	FOO2_A,
+	FOO2_B,
+	FOO2_MISSING,
+	FOO2_COUNT
+};
+const char *foo2[FOO2_COUNT] = { //expected-warning{{incomplete initializer list}}
+	[FOO2_A] = "a",
+	[FOO2_B] = "b",
+};
+
+// complete array initializer
+int foo3[4] = { 1, 1, 1, 1 };
+
+// missing struct initializer in between
+struct {
+	int a, b, c, d;
+} bar1 = {
+	.a = 1,
+	.b = 1,
+	.d = 1
+};
+
+// missing struct initializer at end
+struct {
+	int a, b, c, d;
+} bar2 = {
+	.a = 1,
+	.b = 1,
+	.c = 1
+};
+
+// complete struct initializer
+struct {
+	int a, b, c, d;
+} bar3 = { 1, 1, 1, 1 };