Don't crash generating debug info for VLA in function prototype.

[efriedma]

Summary

Fixes regression from r279445.

[dblaikie]

lib/CodeGen/CGDebugInfo.cpp

2183–2185

You could declare a variable in the new/first if so you don't have to query for the exprsize a second time.

Or you could roll the first if into the second if you want to reduce indentation of the assignment.

Neither's something I find necessary, though - just some thoughts.

lib/CodeGen/CGDebugInfo.cpp

while ((Ty = dyn_cast<ArrayType>(EltTy))) {
     //
     //   struct foo {
     //     int x[0];
     //   };
     int64_t Count = -1; // Count == -1 is an unbounded array.
     if (const auto *CAT = dyn_cast<ConstantArrayType>(Ty))
       Count = CAT->getSize().getZExtValue();
     else if (const auto *VAT = dyn_cast<VariableArrayType>(Ty)) {
+      if (VAT->getSizeExpr()) {
         llvm::APSInt V;
         if (VAT->getSizeExpr()->EvaluateAsInt(V, CGM.getContext()))
           Count = V.getExtValue();
       }
+    }
 
     // FIXME: Verify this is right for VLAs.
     Subscripts.push_back(DBuilder.getOrCreateSubrange(0, Count));
     EltTy = Ty->getElementType();
   }
 
   llvm::DINodeArray SubscriptArray = DBuilder.getOrCreateArray(Subscripts);
 

test/CodeGenCXX/debug-info-vla.cpp

-// RUN: %clang -target x86_64-unknown-unknown -fverbose-asm -g -O0 -S -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang -target x86_64-unknown-unknown -fverbose-asm -g -O0 -S -emit-llvm %s -o - -std=c++11 | FileCheck %s
 
 
 void f(int m) {
   int x[3][m];
 }
 
+int (*fp)(int[][*]) = nullptr;
+
+// CHECK: !DICompositeType(tag: DW_TAG_array_type,
+// CHECK-NOT:                               size:
+// CHECK-SAME:                              align: 32
+// CHECK-SAME:                              elements: [[ELEM_TYPE:![0-9]+]]
+// CHECK: [[ELEM_TYPE]] = !{[[NOCOUNT:.*]]}
+// CHECK: [[NOCOUNT]] = !DISubrange(count: -1)
+//
 // CHECK: !DICompositeType(tag: DW_TAG_array_type,
 // CHECK-NOT:                               size:
 // CHECK-SAME:                              align: 32
 // CHECK-SAME:                              elements: [[ELEM_TYPE:![0-9]+]]
-// CHECK: [[ELEM_TYPE]] = !{[[SUB1:.*]], [[SUB2:.*]]}
-// CHECK: [[SUB1]] = !DISubrange(count: 3)
-// CHECK: [[SUB2]] = !DISubrange(count: -1)
+// CHECK: [[ELEM_TYPE]] = !{[[THREE:.*]], [[NOCOUNT]]}
+// CHECK: [[THREE]] = !DISubrange(count: 3)