Commit da0089c9 authored by Alan Zhao's avatar Alan Zhao
Browse files

[clang] Fix default initializers being ignored when initializing templated aggregate types 

Previously, when checking whether an in-class initializer exists when
performing parenthesized aggregate initialization, Clang checks that the
output of FieldDecl::getInClassInitializer() is non-null. This is
incorrect; if the field is part of a templated type, then
getInClassInitializer() will return nullptr if we haven't called
Sem::BuildCXXDefaultInitExpr(...) before, even if
FieldDecl::hasInClassInitializer() returns true. The end result is that
Clang incorrectly ignores the in class initializer and
value-initializes the field. The fix therefore is to instead call
FieldDecl::hasInClassInitializer(), which is what we do for braced init
lists [0].

Before this patch, Clang does correctly recognize the in-class field
initializer in certain cases. This is Sema::BuildCXXDefaultInitExpr(...)
populates the in class initializer of the corresponding FieldDecl
object. Therefore, if that method was previously called with the same
FieldDecl object, as can happen with a decltype(...) or a braced list
initialization, FieldDecl::getInClassInitializer() will return a
non-null expression, and the field becomes properly initialized.

Fixes 62266

[0]: https://github.com/llvm/llvm-project/blob/be5f35e24f4c15caf3c4aeccddc54c52560c28a0/clang/lib/Sema/SemaInit.cpp#L685

Reviewed By: shafik

Differential Revision: https://reviews.llvm.org/D149389
parent ce357fd4

clang/docs/ReleaseNotes.rst

+3 −0
Original line number Diff line number Diff line
@@ -373,6 +373,9 @@ Bug Fixes to C++ Support 
- Fix bug in the computation of the ``__has_unique_object_representations``

  builtin for types with unnamed bitfields.

  (`#61336 <https://github.com/llvm/llvm-project/issues/61336>`_)

- Fix default member initializers sometimes being ignored when performing

  parenthesized aggregate initialization of templated types.

  (`#62266 <https://github.com/llvm/llvm-project/issues/62266>`_)



Bug Fixes to AST Handling

^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaInit.cpp

+9 −7
Original line number Diff line number Diff line
@@ -5377,14 +5377,16 @@ static void TryOrBuildParenListInitialization( 
          //   The remaining elements are initialized with their default member

          //   initializers, if any

          auto *FD = cast<FieldDecl>(SubEntity.getDecl());

          if (Expr *ICE = FD->getInClassInitializer(); ICE && !VerifyOnly) {

          if (FD->hasInClassInitializer()) {

            if (!VerifyOnly) {

              ExprResult DIE = S.BuildCXXDefaultInitExpr(FD->getLocation(), FD);

              if (DIE.isInvalid())

                return false;

              S.checkInitializerLifetime(SubEntity, DIE.get());

              InitExprs.push_back(DIE.get());

            }

            continue;

          };

          }

        }

        // Remaining class elements without default member initializers and

        // array elements are value initialized:

clang/test/CodeGen/paren-list-agg-init.cpp

+23 −0
Original line number Diff line number Diff line
@@ -90,6 +90,15 @@ namespace gh61145 { 
  };

}



namespace gh62266 {

  // CHECK-DAG: [[STRUCT_H:%.*H.*]] = type { i32, i32 }

  template <int J>

  struct H {

    int i;

    int j = J;

  };

}



// CHECK-DAG: [[A1:@.*a1.*]] = internal constant [[STRUCT_A]] { i8 3, double 2.000000e+00 }, align 8

constexpr A a1(3.1, 2.0);

// CHECK-DAG: [[A2:@.*a2.*]] = internal constant [[STRUCT_A]] { i8 99, double 0.000000e+00 }, align 8
@@ -421,3 +430,17 @@ namespace gh61145 { 
    make2<0>();

  }

}



namespace gh62266 {

  // CHECK: define {{.*}} void {{.*foo20.*}}

  // CHECK-NEXT: entry:

  // CHECK-NEXT: [[H:%.*h.*]] = alloca [[STRUCT_H]], align 4

  // CHECK-NEXT: [[I:%.*i.*]] = getelementptr inbounds [[STRUCT_H]], ptr [[H]], i32 0, i32 0

  // CHECK-NEXT: store i32 1, ptr [[I]], align 4

  // CHECK-NEXT: [[J:%.*j.*]] = getelementptr inbounds [[STRUCT_H]], ptr [[H]], i32 0, i32 1

  // CHECK-NEXT: store i32 2, ptr [[J]], align 4

  // CHECK-NEXT: ret void

  void foo20() {

    H<2> h(1);

  }

}