diff options
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs | 36 |
1 files changed, 33 insertions, 3 deletions
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs index 0f512fcaaaf..1d81d880b8d 100644 --- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs +++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs @@ -1534,6 +1534,19 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> { .. } => { let tag_info = if fallback { + // For MSVC, we generate a union of structs for each variant with an explicit + // discriminant field roughly equivalent to the following C: + // ```c + // union _enum<{name}> { + // struct {variant 0 name} { + // tag$ variant$; + // <variant 0 fields> + // } Variant0; + // <other variant structs> + // } + // ``` + // The natvis in `intrinsic.nativs` then matches on `this.Variant0.variant$` to + // determine which variant is active and then displays it. Some(DirectTag { tag_field: Field::from(tag_field), tag_type_metadata: self.tag_type_metadata.unwrap(), @@ -1613,6 +1626,25 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> { // For MSVC, we will generate a union of two structs, one for the dataful variant and one that just points to // the discriminant field. We also create an enum that contains tag values for the non-dataful variants and // make the discriminant field that type. We then use natvis to render the enum type correctly in Windbg/VS. + // This will generate debuginfo roughly equivalent to the following C: + // ```c + // union _enum<{name}, {min niche}, {max niche}, {dataful variant name} { + // struct dataful_variant { + // <fields in dataful variant> + // }, + // struct discriminant$ { + // enum tag$ { + // <non-dataful variants> + // } discriminant; + // } + // } + // ``` + // The natvis in `intrinsic.natvis` matches on the type name `_enum<*, *, *, *>` + // and evaluates `this.discriminant$.discriminant`. If the value is between + // the min niche and max niche, then the enum is in the dataful variant and + // `this.dataful_variant` is rendered. Otherwise, the enum is in one of the + // non-dataful variants. In that case, we just need to render the name of the + // `this.discriminant$.discriminant` enum. if fallback { let unique_type_id = debug_context(cx) .type_map @@ -1938,9 +1970,7 @@ fn describe_enum_variant( // We have the layout of an enum variant, we need the layout of the outer enum let enum_layout = cx.layout_of(layout.ty); let offset = enum_layout.fields.offset(tag_field.as_usize()); - let tag_name = - if cx.tcx.sess.target.is_like_msvc { "variant$" } else { "RUST$ENUM$DISR" }; - let args = (tag_name.to_owned(), enum_layout.field(cx, tag_field.as_usize()).ty); + let args = ("variant$".to_owned(), enum_layout.field(cx, tag_field.as_usize()).ty); (Some(offset), Some(args)) } _ => (None, None), |