[clang][ItaniumMangle] Check SizeExpr for DependentSizedArrayType (PR49478)

[oToToT]

Summary

As ArrayType::ArrayType mentioned in clang/lib/AST/Type.cpp, a DependentSizedArrayType might not have size expression because it it used as the type of a dependent array of unknown bound with a dependent braced initializer.

Thus, I add a check when mangling array of that type.

This should fix https://bugs.llvm.org/show_bug.cgi?id=49478

[oToToT]

Remove redundant whitespace in comment.

[yaxunl]

clang/test/AST/ast-dump-array-json.cpp

7

I am not sure if this test tests the code you change since the mangled variable name does not encode type.

[oToToT]

clang/test/AST/ast-dump-array-json.cpp

7

I think this test my code. Or, at least, this test will trigger a runtime error in the latest clang without this patch when mangling A::Test.

Also, maybe I could try construct a test to mangle variable with element type if needed.

WDYT?

[rsmith]

clang/test/AST/ast-dump-array-json.cpp

7

I would like to see a test that verifies the A<type>_ mangling is produced.

[oToToT]

clang/test/AST/ast-dump-array-json.cpp

7

Ah, you're right! After some investigation, I found that this CHECK in the test doesn't really check my patch.
This test only ensure that clang won't get runtime error when handling this file.

However, I can't find any clever way to construct a test like this to ensure the output of CXXNameMangler::mangleType(const DependentSizedArrayType *). (It is called here only for checking ABI tags, so I guess no output will be displayed).

I will try replace this test with a unittest to check the output.

[oToToT]

Updated tests to check mangled type name.

However, I not sure whether it is proper to put the tests here.

[oToToT]

Remove redundant trailing spaces.

Sorry for not checking this at the first time I submit.

clang/lib/AST/ItaniumMangle.cpp

void CXXNameMangler::mangleType(const VariableArrayType *T) {
   // decayed vla types (size 0) will just be skipped.
   if (T->getSizeExpr())
     mangleExpression(T->getSizeExpr());
   Out << '_';
   mangleType(T->getElementType());
 }
 void CXXNameMangler::mangleType(const DependentSizedArrayType *T) {
   Out << 'A';
+  // A DependentSizedArrayType might not have size expression as below
+  // 
+  //   template<int ...N> int arr[] = {N...};
+  if (T->getSizeExpr())
     mangleExpression(T->getSizeExpr());
   Out << '_';
   mangleType(T->getElementType());
 }
 void CXXNameMangler::mangleType(const IncompleteArrayType *T) {
   Out << "A_";
   mangleType(T->getElementType());
 }
 

clang/test/AST/ast-dump-array-json.cpp

+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -ast-dump=json -ast-dump-filter Test %s | FileCheck %s
+
+template<unsigned... N> struct A { static const int Test[]; };
+template<unsigned... N> const int A<N...>::Test[] = { N... };
+
+// CHECK: "mangledName": "_ZN1A4TestE",
+// CHECK: "mangledName": "_ZN1A4TestE",