[Sema] Issue a warning for integer overflow in struct initializer

Clang wasn't issuing a warning when compiling the following code:

struct s {
  unsigned x;
} s = {
  .x = 4 * 1024 * 1024 * 1024
};

rdar://problem/23399683

Differential Revision: http://reviews.llvm.org/D15097

llvm-svn: 257357

clang/lib/Sema/SemaChecking.cpp

@@ -7853,6 +7853,10 @@ void Sema::CheckBoolLikeConversion(Expr *E, SourceLocation CC) {
 void Sema::CheckForIntOverflow (Expr *E) {
   if (isa<BinaryOperator>(E->IgnoreParenCasts()))
     E->IgnoreParenCasts()->EvaluateForOverflow(Context);
+  else if (auto InitList = dyn_cast<InitListExpr>(E))
+    for (Expr *E : InitList->inits())
+      if (isa<BinaryOperator>(E->IgnoreParenCasts()))
+        E->IgnoreParenCasts()->EvaluateForOverflow(Context);
 }
 
 namespace {

clang/test/Sema/integer-overflow.c

@@ -145,3 +145,11 @@ uint64_t check_integer_overflows(int i) {
 // expected-warning@+1 2{{overflow in expression; result is 536870912 with type 'int'}}
   return ((4608 * 1024 * 1024) + ((uint64_t)(4608 * 1024 * 1024)));
 }
+
+struct s {
+  unsigned x;
+  unsigned y;
+} s = {
+  .y = 5,
+  .x = 4 * 1024 * 1024 * 1024  // expected-warning {{overflow in expression; result is 0 with type 'int'}}
+};