Rollup merge of rust-lang#124458 - VladimirMakaev:lldb-enum-formatter…

…, r=Mark-Simulacrum

Implement lldb formattter for "clang encoded" enums (LLDB 18.1+)

## Summary:

fixes rust-lang#79530

I landed a fix last year to enable `DW_TAG_variant_part` encoding in LLDBs (https://reviews.llvm.org/D149213). This PR is a corresponding fix in synthetic formatters to decode that information.

This is in no way perfect implementation but at least it improves the status quo. But most types of enums will be visible and debuggable in some way.

I've also updated most of the existing tests that touch enums and re-enabled test cases based on LLDB for enums.

## Test Plan:
ran tests `./x test tests/debuginfo/`. Also tested manually in LLDB CLI and LLDB VSCode

## Other Thoughs:
A better approach would probably be adopting [formatters from codelldb](https://github.com/vadimcn/codelldb/blob/master/formatters/rust.py). There is some neat hack that hooks up summary provider via synthetic provider which can ultimately fix more display issues for Rust types and enums too. But getting it to work well might take more time that I have right now.

src/etc/lldb_lookup.py

@@ -86,7 +86,8 @@ def synthetic_lookup(valobj, dict):
         return synthetic_lookup(valobj.GetChildAtIndex(discriminant), dict)
     if rust_type == RustType.SINGLETON_ENUM:
         return synthetic_lookup(valobj.GetChildAtIndex(0), dict)
-
+    if rust_type == RustType.ENUM:
+        return ClangEncodedEnumProvider(valobj, dict)
     if rust_type == RustType.STD_VEC:
         return StdVecSyntheticProvider(valobj, dict)
     if rust_type == RustType.STD_VEC_DEQUE:

src/etc/lldb_providers.py

@@ -247,6 +247,58 @@ def has_children(self):
         # type: () -> bool
         return True
 
+class ClangEncodedEnumProvider:
+    """Pretty-printer for 'clang-encoded' enums support implemented in LLDB"""
+    DISCRIMINANT_MEMBER_NAME = "$discr$"
+    VALUE_MEMBER_NAME = "value"
+
+    def __init__(self, valobj, dict):
+        self.valobj = valobj
+        self.update()
+
+    def has_children(self):
+       return True
+
+    def num_children(self):
+        if self.is_default:
+            return 1
+        return 2
+
+    def get_child_index(self, name):
+        if name == ClangEncodedEnumProvider.VALUE_MEMBER_NAME:
+            return 0
+        if name == ClangEncodedEnumProvider.DISCRIMINANT_MEMBER_NAME:
+            return 1
+        return -1
+
+    def get_child_at_index(self, index):
+        if index == 0:
+            return self.variant.GetChildMemberWithName(ClangEncodedEnumProvider.VALUE_MEMBER_NAME)
+        if index == 1:
+            return self.variant.GetChildMemberWithName(
+                ClangEncodedEnumProvider.DISCRIMINANT_MEMBER_NAME)
+
+
+    def update(self):
+        all_variants = self.valobj.GetChildAtIndex(0)
+        index = self._getCurrentVariantIndex(all_variants)
+        self.variant = all_variants.GetChildAtIndex(index)
+        self.is_default = self.variant.GetIndexOfChildWithName(
+            ClangEncodedEnumProvider.DISCRIMINANT_MEMBER_NAME) == -1
+
+    def _getCurrentVariantIndex(self, all_variants):
+        default_index = 0
+        for i in range(all_variants.GetNumChildren()):
+            variant = all_variants.GetChildAtIndex(i)
+            discr = variant.GetChildMemberWithName(
+                ClangEncodedEnumProvider.DISCRIMINANT_MEMBER_NAME)
+            if discr.IsValid():
+                discr_unsigned_value = discr.GetValueAsUnsigned()
+                if variant.GetName() == f"$variant${discr_unsigned_value}":
+                    return i
+            else:
+                default_index = i
+        return default_index
 
 class TupleSyntheticProvider:
     """Pretty-printer for tuples and tuple enum variants"""

src/etc/rust_types.py

@@ -60,6 +60,7 @@ class RustType(object):
 
 ENCODED_ENUM_PREFIX = "RUST$ENCODED$ENUM$"
 ENUM_DISR_FIELD_NAME = "<<variant>>"
+ENUM_LLDB_ENCODED_VARIANTS = "$variants$"
 
 STD_TYPE_TO_REGEX = {
     RustType.STD_STRING: STD_STRING_REGEX,
@@ -96,7 +97,11 @@ def classify_struct(name, fields):
         if regex.match(name):
             return ty
 
-    if fields[0].name == ENUM_DISR_FIELD_NAME:
+    # <<variant>> is emitted by GDB while LLDB(18.1+) emits "$variants$"
+    if (
+        fields[0].name == ENUM_DISR_FIELD_NAME
+        or fields[0].name == ENUM_LLDB_ENCODED_VARIANTS
+    ):
         return RustType.ENUM
 
     if is_tuple_fields(fields):

tests/debuginfo/borrowed-enum.rs

@@ -1,6 +1,6 @@
 // Require a gdb or lldb that can read DW_TAG_variant_part.
 //@ min-gdb-version: 8.2
-//@ needs-rust-lldb
+//@ min-lldb-version: 1800
 
 //@ compile-flags:-g
 
@@ -23,10 +23,13 @@
 // lldb-command:run
 
 // lldb-command:v *the_a_ref
+// lldbg-check:(borrowed_enum::ABC) *the_a_ref = { value = { x = 0 y = 8970181431921507452 } $discr$ = 0 }
 // lldbr-check:(borrowed_enum::ABC::TheA) *the_a_ref = TheA { TheA: 0, TheB: 8970181431921507452 }
 // lldb-command:v *the_b_ref
+// lldbg-check:(borrowed_enum::ABC) *the_b_ref = { value = { 0 = 0 1 = 286331153 2 = 286331153 } $discr$ = 1 }
 // lldbr-check:(borrowed_enum::ABC::TheB) *the_b_ref = { = 0 = 286331153 = 286331153 }
 // lldb-command:v *univariant_ref
+// lldbg-check:(borrowed_enum::Univariant) *univariant_ref = { value = { 0 = 4820353753753434 } }
 // lldbr-check:(borrowed_enum::Univariant) *univariant_ref = { TheOnlyCase = { = 4820353753753434 } }
 
 #![allow(unused_variables)]

tests/debuginfo/coroutine-objects.rs

@@ -1,8 +1,9 @@
 // Require a gdb that can read DW_TAG_variant_part.
 //@ min-gdb-version: 8.2
+//@ min-lldb-version: 1800
 
-// LLDB without native Rust support cannot read DW_TAG_variant_part,
-// so it prints nothing for coroutines. But those tests are kept to
+// LLDB (18.1+) now supports DW_TAG_variant_part, but there is some bug in either compiler or LLDB
+// with memory layout of discriminant for this particular enum
 // ensure that LLDB won't crash at least (like #57822).
 
 //@ compile-flags:-g
@@ -26,16 +27,7 @@
 
 // lldb-command:run
 // lldb-command:v b
-// lldbg-check:(coroutine_objects::main::{coroutine_env#0}) b =
-// lldb-command:continue
-// lldb-command:v b
-// lldbg-check:(coroutine_objects::main::{coroutine_env#0}) b =
-// lldb-command:continue
-// lldb-command:v b
-// lldbg-check:(coroutine_objects::main::{coroutine_env#0}) b =
-// lldb-command:continue
-// lldb-command:v b
-// lldbg-check:(coroutine_objects::main::{coroutine_env#0}) b =
+// lldb-check:(coroutine_objects::main::{coroutine_env#0}) b = { value = { _ref__a = 0x[...] } $discr$ = ',' }
 
 // === CDB TESTS ===================================================================================
 

tests/debuginfo/enum-thinlto.rs

@@ -1,6 +1,6 @@
 // Require a gdb that can read DW_TAG_variant_part.
 //@ min-gdb-version: 8.2
-
+//@ min-lldb-version: 1800
 //@ compile-flags:-g -Z thinlto
 
 // === GDB TESTS ===================================================================================
@@ -15,7 +15,7 @@
 // lldb-command:run
 
 // lldb-command:v *abc
-// lldbg-check:(enum_thinlto::ABC) *abc =
+// lldbg-check:(enum_thinlto::ABC) *abc = { value = { x = 0 y = 8970181431921507452 } $discr$ = 0 }
 // lldbr-check:(enum_thinlto::ABC) *abc = (x = 0, y = 8970181431921507452)
 
 #![allow(unused_variables)]

tests/debuginfo/issue-57822.rs

@@ -3,7 +3,7 @@
 
 // Require a gdb that can read DW_TAG_variant_part.
 //@ min-gdb-version: 8.2
-
+//@ min-lldb-version: 1800
 //@ compile-flags:-g
 
 // === GDB TESTS ===================================================================================
@@ -24,7 +24,7 @@
 // lldbg-check:(issue_57822::main::{closure_env#1}) g = { f = { x = 1 } }
 
 // lldb-command:v b
-// lldbg-check:(issue_57822::main::{coroutine_env#3}) b =
+// lldbg-check:(issue_57822::main::{coroutine_env#3}) b = { value = { a = { value = { y = 2 } $discr$ = '\x02' } } $discr$ = '\x02' }
 
 #![feature(omit_gdb_pretty_printer_section, coroutines, coroutine_trait, stmt_expr_attributes)]
 #![omit_gdb_pretty_printer_section]

tests/debuginfo/msvc-pretty-enums.rs

@@ -1,5 +1,84 @@
-//@ only-cdb
+//@ min-lldb-version: 1800
+//@ ignore-gdb
 //@ compile-flags:-g
+
+// === LLDB TESTS ==================================================================================
+
+// lldb-command:run
+// lldb-command:v a
+// lldbg-check:(core::option::Option<msvc_pretty_enums::CStyleEnum>) a = { value = { 0 = Low } }
+
+// lldb-command:v b
+// lldbg-check:(core::option::Option<msvc_pretty_enums::CStyleEnum>) b = { value = $discr$ = '\x01' }
+
+// lldb-command:v c
+// lldbg-check:(msvc_pretty_enums::NicheLayoutEnum) c = { value = $discr$ = '\x11' }
+
+// lldb-command:v d
+// lldbg-check:(msvc_pretty_enums::NicheLayoutEnum) d = { value = { my_data = High } }
+
+// lldb-command:v e
+// lldbg-check:(msvc_pretty_enums::NicheLayoutEnum) e = { value = $discr$ = '\x13' }
+
+// lldb-command:v h
+// lldbg-check:(core::option::Option<u32>) h = { value = { 0 = 12 } $discr$ = 1 }
+
+// lldb-command:v i
+// lldbg-check:(core::option::Option<u32>) i = { value = $discr$ = 0 }
+
+// lldb-command:v j
+// lldbg-check:(msvc_pretty_enums::CStyleEnum) j = High
+
+// lldb-command:v k
+// lldbg-check:(core::option::Option<alloc::string::String>) k = { value = { 0 = "IAMA optional string!" { vec = size=21 { [0] = 'I' [1] = 'A' [2] = 'M' [3] = 'A' [4] = ' ' [5] = 'o' [6] = 'p' [7] = 't' [8] = 'i' [9] = 'o' [10] = 'n' [11] = 'a' [12] = 'l' [13] = ' ' [14] = 's' [15] = 't' [16] = 'r' [17] = 'i' [18] = 'n' [19] = 'g' [20] = '!' } } } }
+
+// lldb-command:v l
+// lldbg-check:(core::result::Result<u32, msvc_pretty_enums::Empty>) l = { value = { 0 = {} } }
+
+// lldb-command:v niche128_some
+// lldbg-check:(core::option::Option<core::num::nonzero::NonZero<i128>>) niche128_some = { value = $discr$ = 123456 }
+
+// lldb-command:v niche128_none
+// lldbg-check:(core::option::Option<core::num::nonzero::NonZero<i128>>) niche128_none = { value = $discr$ = 0 }
+
+// lldb-command:v wrapping_niche128_untagged
+// lldbg-check:(msvc_pretty_enums::Wrapping128Niche) wrapping_niche128_untagged = { value = { 0 = { 0 = 340282366920938463463374607431768211454 } } }
+
+// lldb-command:v wrapping_niche128_none1
+// lldbg-check:(msvc_pretty_enums::Wrapping128Niche) wrapping_niche128_none1 = { value = { 0 = { 0 = 2 } } }
+
+// lldb-command:v direct_tag_128_a
+// lldbg-check:(msvc_pretty_enums::DirectTag128) direct_tag_128_a = { value = { 0 = 42 } $discr$ = 0 }
+
+// lldb-command:v direct_tag_128_b
+// lldbg-check:(msvc_pretty_enums::DirectTag128) direct_tag_128_b = { value = { 0 = 137 } $discr$ = 1 }
+
+// &u32 is incorrectly formatted and LLDB thinks it's a char* so skipping niche_w_fields_1_some
+
+// lldb-command:v niche_w_fields_1_none
+// lldbg-check:(msvc_pretty_enums::NicheLayoutWithFields1) niche_w_fields_1_none = { value = { 0 = 99 } $discr$ = 1 }
+
+// lldb-command:v niche_w_fields_2_some
+// lldbg-check:(msvc_pretty_enums::NicheLayoutWithFields2) niche_w_fields_2_some = { value = { 0 = 800 { __0 = { 0 = 800 } } 1 = 900 } $discr$ = 0 }
+
+// lldb-command:v niche_w_fields_3_some
+// lldbg-check:(msvc_pretty_enums::NicheLayoutWithFields3) niche_w_fields_3_some = { value = { 0 = '\x89' 1 = true } }
+
+// lldb-command:v niche_w_fields_3_niche3
+// lldbg-check:(msvc_pretty_enums::NicheLayoutWithFields3) niche_w_fields_3_niche3 = { value = { 0 = '"' } $discr$ = '\x04' }
+
+// lldb-command:v arbitrary_discr1
+// lldbg-check:(msvc_pretty_enums::ArbitraryDiscr) arbitrary_discr1 = { value = { 0 = 1234 } $discr$ = 1000 }
+
+// lldb-command:v arbitrary_discr2
+// lldbg-check:(msvc_pretty_enums::ArbitraryDiscr) arbitrary_discr2 = { value = { 0 = 5678 } $discr$ = 5000000 }
+
+// === CDB TESTS ==================================================================================
+// cdb-command: g
+//
+// cdb-command: dx a
+// cdb-check:a                : Some [Type: enum2$<core::option::Option<msvc_pretty_enums::CStyleEnum> >]
+// cdb-check:    [+0x000] __0              : Low (0x2) [Type: msvc_pretty_enums::CStyleEnum]
 //
 // cdb-command: g
 //

tests/debuginfo/struct-style-enum.rs

@@ -1,7 +1,6 @@
 // Require a gdb or lldb that can read DW_TAG_variant_part.
 //@ min-gdb-version: 8.2
-//@ needs-rust-lldb
-
+//@ min-lldb-version: 1800
 //@ compile-flags:-g
 
 // === GDB TESTS ===================================================================================
@@ -27,15 +26,19 @@
 // lldb-command:run
 
 // lldb-command:v case1
+// lldbg-check:(struct_style_enum::Regular) case1 = { value = { a = 0 b = 31868 c = 31868 d = 31868 e = 31868 } $discr$ = 0 }
 // lldbr-check:(struct_style_enum::Regular::Case1) case1 = { a = 0 b = 31868 c = 31868 d = 31868 e = 31868 }
 
 // lldb-command:v case2
+// lldbg-check:(struct_style_enum::Regular) case2 = { value = { a = 0 b = 286331153 c = 286331153 } $discr$ = 1 }
 // lldbr-check:(struct_style_enum::Regular::Case2) case2 = Case2 { Case1: 0, Case2: 286331153, Case3: 286331153 }
 
 // lldb-command:v case3
+// lldbg-check:(struct_style_enum::Regular) case3 = { value = { a = 0 b = 6438275382588823897 } $discr$ = 2 }
 // lldbr-check:(struct_style_enum::Regular::Case3) case3 = Case3 { Case1: 0, Case2: 6438275382588823897 }
 
 // lldb-command:v univariant
+// lldbg-check:(struct_style_enum::Univariant) univariant = { value = { a = -1 } }
 // lldbr-check:(struct_style_enum::Univariant) univariant = Univariant { TheOnlyCase: TheOnlyCase { a: -1 } }
 
 #![allow(unused_variables)]

tests/debuginfo/tuple-style-enum.rs

@@ -1,6 +1,6 @@
 // Require a gdb or lldb that can read DW_TAG_variant_part.
 //@ min-gdb-version: 8.2
-//@ needs-rust-lldb
+//@ min-lldb-version: 1800
 
 //@ compile-flags:-g
 
@@ -27,15 +27,19 @@
 // lldb-command:run
 
 // lldb-command:v case1
+// lldbg-check:(tuple_style_enum::Regular) case1 = { value = { 0 = 0 1 = 31868 2 = 31868 3 = 31868 4 = 31868 } $discr$ = 0 }
 // lldbr-check:(tuple_style_enum::Regular::Case1) case1 = { = 0 = 31868 = 31868 = 31868 = 31868 }
 
 // lldb-command:v case2
+// lldbg-check:(tuple_style_enum::Regular) case2 = { value = { 0 = 0 1 = 286331153 2 = 286331153 } $discr$ = 1 }
 // lldbr-check:(tuple_style_enum::Regular::Case2) case2 = Case2 { Case1: 0, Case2: 286331153, Case3: 286331153 }
 
 // lldb-command:v case3
+// lldbg-check:(tuple_style_enum::Regular) case3 = { value = { 0 = 0 1 = 6438275382588823897 } $discr$ = 2 }
 // lldbr-check:(tuple_style_enum::Regular::Case3) case3 = Case3 { Case1: 0, Case2: 6438275382588823897 }
 
 // lldb-command:v univariant
+// lldbg-check:(tuple_style_enum::Univariant) univariant = { value = { 0 = -1 } }
 // lldbr-check:(tuple_style_enum::Univariant) univariant = { TheOnlyCase = { = -1 } }
 
 #![allow(unused_variables)]

tests/debuginfo/unique-enum.rs

@@ -1,6 +1,6 @@
 // Require a gdb or lldb that can read DW_TAG_variant_part.
 //@ min-gdb-version: 8.2
-//@ needs-rust-lldb
+//@ min-lldb-version: 1800
 
 //@ compile-flags:-g
 
@@ -23,12 +23,15 @@
 // lldb-command:run
 
 // lldb-command:v *the_a
+// lldbg-check:(unique_enum::ABC) *the_a = { value = { x = 0 y = 8970181431921507452 } $discr$ = 0 }
 // lldbr-check:(unique_enum::ABC::TheA) *the_a = TheA { TheA: 0, TheB: 8970181431921507452 }
 
 // lldb-command:v *the_b
+// lldbg-check:(unique_enum::ABC) *the_b = { value = { 0 = 0 1 = 286331153 2 = 286331153 } $discr$ = 1 }
 // lldbr-check:(unique_enum::ABC::TheB) *the_b = { = 0 = 286331153 = 286331153 }
 
 // lldb-command:v *univariant
+// lldbg-check:(unique_enum::Univariant) *univariant = { value = { 0 = 123234 } }
 // lldbr-check:(unique_enum::Univariant) *univariant = { TheOnlyCase = { = 123234 } }
 
 #![allow(unused_variables)]