[Lldb-commits] [lldb] Fix a bug where an error was emitted for GCC union types. (PR #159401)
Greg Clayton via lldb-commits
lldb-commits at lists.llvm.org
Wed Sep 17 10:05:26 PDT 2025
https://github.com/clayborg created https://github.com/llvm/llvm-project/pull/159401
GCC doesn't add DW_AT_data_member_location attributes to the DW_TAG_member children of DW_TAG_union_type types. An error was being emitted incorrectly for these cases fr om the DWARFASTParserClang. This fixes that issue and adds a test.
>From 5971113fea4e156885cc4ccb5e132c7ba1b65235 Mon Sep 17 00:00:00 2001
From: Greg Clayton <clayborg at gmail.com>
Date: Wed, 17 Sep 2025 10:04:07 -0700
Subject: [PATCH] Fix a bug where an error was emitted for GCC union types.
GCC doesn't add DW_AT_data_member_location attributes to the DW_TAG_member children of DW_TAG_union_type types. An error was being emitted incorrectly for these cases fr
om the DWARFASTParserClang. This fixes that issue and adds a test.
---
.../SymbolFile/DWARF/DWARFASTParserClang.cpp | 6 +-
.../DWARF/union-types-no-member-location.yaml | 182 ++++++++++++++++++
2 files changed, 187 insertions(+), 1 deletion(-)
create mode 100644 lldb/test/Shell/SymbolFile/DWARF/union-types-no-member-location.yaml
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index 5ffb4423969ca..f1e73d73a733b 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -3142,7 +3142,11 @@ void DWARFASTParserClang::ParseSingleMember(
uint64_t parent_byte_size =
parent_die.GetAttributeValueAsUnsigned(DW_AT_byte_size, UINT64_MAX);
- if (attrs.member_byte_offset >= parent_byte_size) {
+ // If the attrs.member_byte_offset is still set to UINT32_MAX this means
+ // that the DW_TAG_member didn't have a DW_AT_data_member_location, so
+ // don't emit an error if this is the case.
+ if (attrs.member_byte_offset != UINT32_MAX &&
+ attrs.member_byte_offset >= parent_byte_size) {
if (member_array_size != 1 &&
(member_array_size != 0 ||
attrs.member_byte_offset > parent_byte_size)) {
diff --git a/lldb/test/Shell/SymbolFile/DWARF/union-types-no-member-location.yaml b/lldb/test/Shell/SymbolFile/DWARF/union-types-no-member-location.yaml
new file mode 100644
index 0000000000000..e2d32bb47bf59
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/union-types-no-member-location.yaml
@@ -0,0 +1,182 @@
+# This test produces DWARF that contains a union type whose DW_TAG_member does
+# not have a DW_AT_data_member_location set to zero. This is how GCC emits
+# debug information for unions. There was code in the DWARFASTParserClang that
+# was emitting an invalid error in this case. This test verifies that this
+# error does not get emitted.
+#
+# 0x0000000b: DW_TAG_compile_unit
+# DW_AT_name ("main.cpp")
+# DW_AT_language (DW_LANG_C)
+#
+# 0x00000011: DW_TAG_base_type
+# DW_AT_name ("int")
+# DW_AT_encoding (DW_ATE_signed_char)
+# DW_AT_byte_size (0x04)
+#
+# 0x00000018: DW_TAG_base_type
+# DW_AT_name ("__ARRAY_SIZE_TYPE__")
+# DW_AT_encoding (DW_ATE_unsigned)
+# DW_AT_byte_size (0x08)
+#
+# 0x0000001f: DW_TAG_array_type
+# DW_AT_type (0x00000011 "int")
+#
+# 0x00000024: DW_TAG_subrange_type
+# DW_AT_type (0x00000018 "__ARRAY_SIZE_TYPE__")
+# DW_AT_count (0x20)
+#
+# 0x0000002a: NULL
+#
+# 0x0000002b: DW_TAG_union_type
+# DW_AT_name ("UnionType")
+# DW_AT_byte_size (0x20)
+#
+# 0x00000031: DW_TAG_member
+# DW_AT_name ("array")
+# DW_AT_type (0x0000001f "int[32]")
+#
+# 0x0000003a: NULL
+#
+# 0x0000003b: DW_TAG_subprogram
+# DW_AT_low_pc (0x0000000000001000)
+# DW_AT_high_pc (0x0000000000001050)
+# DW_AT_name ("foo")
+# DW_AT_type (0x00000031 "array")
+#
+# 0x00000054: NULL
+
+# RUN: yaml2obj %s > %t
+# RUN: lldb-test symbols --name=UnionType --find=type %t > %t.stdout
+# RUN: cat %t.stdout | FileCheck --check-prefix=STDOUT %s
+# RUN: lldb-test symbols --name=UnionType --find=type %t 2> %t.stderr
+# RUN: cat %t.stderr | FileCheck --check-prefix=STDERR %s
+
+# STDOUT: Found 1 types:
+# STDOUT: 0x{{[0-9a-fA-F]+}}: Type{0x0000002b} , name = "UnionType", size = 32, compiler_type = 0x{{[0-9a-fA-F]+}} union UnionType {
+
+# STDERR-NOT: error: union-types-no-member-location.yaml.tmp 0x00000031: DW_TAG_member 'array' refers to type 0x000000000000001f which extends beyond the bounds of 0x0000002b
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_EXEC
+ Machine: EM_X86_64
+DWARF:
+ debug_str:
+ - ''
+ - main.cpp
+ - int
+ - __ARRAY_SIZE_TYPE__
+ - UnionType
+ - array
+ debug_abbrev:
+ - ID: 0
+ Table:
+ - Code: 0x1
+ Tag: DW_TAG_compile_unit
+ Children: DW_CHILDREN_yes
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_strp
+ - Attribute: DW_AT_language
+ Form: DW_FORM_udata
+ - Code: 0x2
+ Tag: DW_TAG_base_type
+ Children: DW_CHILDREN_no
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_strp
+ - Attribute: DW_AT_encoding
+ Form: DW_FORM_data1
+ - Attribute: DW_AT_byte_size
+ Form: DW_FORM_data1
+ - Code: 0x3
+ Tag: DW_TAG_array_type
+ Children: DW_CHILDREN_yes
+ Attributes:
+ - Attribute: DW_AT_type
+ Form: DW_FORM_ref4
+ - Code: 0x4
+ Tag: DW_TAG_subrange_type
+ Children: DW_CHILDREN_no
+ Attributes:
+ - Attribute: DW_AT_type
+ Form: DW_FORM_ref4
+ - Attribute: DW_AT_count
+ Form: DW_FORM_data1
+ - Code: 0x5
+ Tag: DW_TAG_union_type
+ Children: DW_CHILDREN_yes
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_strp
+ - Attribute: DW_AT_byte_size
+ Form: DW_FORM_data1
+ - Code: 0x6
+ Tag: DW_TAG_member
+ Children: DW_CHILDREN_no
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_strp
+ - Attribute: DW_AT_type
+ Form: DW_FORM_ref4
+ - Code: 0x7
+ Tag: DW_TAG_subprogram
+ Children: DW_CHILDREN_no
+ Attributes:
+ - Attribute: DW_AT_low_pc
+ Form: DW_FORM_addr
+ - Attribute: DW_AT_high_pc
+ Form: DW_FORM_addr
+ - Attribute: DW_AT_name
+ Form: DW_FORM_string
+ - Attribute: DW_AT_type
+ Form: DW_FORM_ref4
+ debug_info:
+ - Length: 0x51
+ Version: 4
+ AbbrevTableID: 0
+ AbbrOffset: 0x0
+ AddrSize: 8
+ Entries:
+ - AbbrCode: 0x1
+ Values:
+ - Value: 0x1
+ - Value: 0x2
+ - AbbrCode: 0x2
+ Values:
+ - Value: 0xA
+ - Value: 0x6
+ - Value: 0x4
+ - AbbrCode: 0x2
+ Values:
+ - Value: 0xE
+ - Value: 0x7
+ - Value: 0x8
+ - AbbrCode: 0x3
+ Values:
+ - Value: 0x11
+ - AbbrCode: 0x4
+ Values:
+ - Value: 0x18
+ - Value: 0x20
+ - AbbrCode: 0x0
+ - AbbrCode: 0x5
+ Values:
+ - Value: 0x22
+ - Value: 0x20
+ - AbbrCode: 0x6
+ Values:
+ - Value: 0x2C
+ - Value: 0x1F
+ - AbbrCode: 0x0
+ - AbbrCode: 0x7
+ Values:
+ - Value: 0x1000
+ - Value: 0x1050
+ - Value: 0xDEADBEEFDEADBEEF
+ CStr: foo
+ - Value: 0x31
+ - AbbrCode: 0x0
+...
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