Re: [PATCH] c++: ICE with scoped enum in switch condition [PR114451]

[Jason Merrill <jason@redhat.com>]

On 3/29/24 18:31, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13?

OK.

> -- >8 --
> Here we ICE when gimplifying
> 
>    enum class Type { Pawn };
>    struct Piece {
>      Type type : 4;
>    };
>    void foo() {
>      switch (Piece().type)
>        case Type::Pawn:;
>    }
> 
> because we ended up with TYPE_PRECISION (cond) < TYPE_PRECISION (case).
> That's because the case expr type here is the unlowered type Type,
> whereas the conditional's type is the lowered <unnamed-signed:4>.  This
> is not supposed to happen: see the comment in pop_switch around the
> is_bitfield_expr_with_lowered_type check.
> 
> But here we did not revert to the lowered SWITCH_STMT_TYPE, because
> the conditional contains a TARGET_EXPR, which has side-effects, which
> means that finish_switch_cond -> maybe_cleanup_point_expr wraps it
> in a CLEANUP_POINT_EXPR.  And is_bitfield_expr_with_lowered_type does
> not see through those.
> 
> 	PR c++/103825
> 
> gcc/cp/ChangeLog:
> 
> 	* typeck.cc (is_bitfield_expr_with_lowered_type): Handle
> 	CLEANUP_POINT_EXPR.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/enum44.C: New test.
> ---
>   gcc/cp/typeck.cc                    |  1 +
>   gcc/testsuite/g++.dg/cpp0x/enum44.C | 30 +++++++++++++++++++++++++++++
>   2 files changed, 31 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/enum44.C
> 
> diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
> index f5a0a2273be..9a096b51d55 100644
> --- a/gcc/cp/typeck.cc
> +++ b/gcc/cp/typeck.cc
> @@ -2400,6 +2400,7 @@ is_bitfield_expr_with_lowered_type (const_tree exp)
>       case NEGATE_EXPR:
>       case NON_LVALUE_EXPR:
>       case BIT_NOT_EXPR:
> +    case CLEANUP_POINT_EXPR:
>         return is_bitfield_expr_with_lowered_type (TREE_OPERAND (exp, 0));
>   
>       case COMPONENT_REF:
> diff --git a/gcc/testsuite/g++.dg/cpp0x/enum44.C b/gcc/testsuite/g++.dg/cpp0x/enum44.C
> new file mode 100644
> index 00000000000..92408c92217
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/enum44.C
> @@ -0,0 +1,30 @@
> +// PR c++/103825
> +// { dg-do compile { target c++11 } }
> +
> +enum class Type { Pawn };
> +struct Piece {
> +  Type type : 4;
> +};
> +
> +void
> +foo ()
> +{
> +  switch (Piece().type)
> +    case Type::Pawn:;
> +
> +  auto x = Piece().type;
> +  switch (x)
> +    case Type::Pawn:;
> +}
> +
> +enum class En {A};
> +struct St {En field :1;};
> +
> +void
> +bar ()
> +{
> +  volatile St s = {En::A};
> +  switch(s.field) {
> +    case En::A : break;
> +  }
> +}
> 
> base-commit: 4c18ace1cb69a31af4ac719850a66de79ed12e93