Fix a bug where an error was emitted for GCC union types. #159401
Merged
+187
−1
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
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.
|
@llvm/pr-subscribers-lldb Author: Greg Clayton (clayborg) ChangesGCC 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. Full diff: https://github.com/llvm/llvm-project/pull/159401.diff 2 Files Affected:
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
+...
|
|
LGTM, but maybe wait a few days for one of the actually active contributors before merging |
Michael137
reviewed
Sep 22, 2025
| // 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 && |
There was a problem hiding this comment.
LGTM
Though there's a couple of follow-ups i think we could do:
- Would be nice if
member_byte_offsetwas an optional - Why is Clang emitting
DW_AT_data_member_locationfor union members? Aren't they always0x0anyway. I assume that's why GCC chooses to omit them. Would be nice for Clang and GCC to align on this. - The history of this codeblock is quite interesting. It seems to work around a Clang debug-info generation bug from before 2012 (around Clang-4). Looks like what we're trying to do here is to fixup the array type from
arr[1]toarr[0]. I'm not even sure if this still works (there are no tests, prior to the one you added).
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/163/builds/27072 Here is the relevant piece of the build log for the reference |
|
The following buildbots are broken afer this patch: Please revert or fix ASAP. |
|
I think this is just a platform dependent formatting thing that means we don't have the |
DavidSpickett
added a commit
that referenced
this pull request
Sep 25, 2025
Fixes #159401 On Windows there is no hex prefix, I suspect because somewhere we print a pointer. I'd prefer to fix that itself but can't get to a Windows machine at the moment. It's not important to the purpose of the test anyway.
mahesh-attarde
pushed a commit
to mahesh-attarde/llvm-project
that referenced
this pull request
Oct 3, 2025
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.
mahesh-attarde
pushed a commit
to mahesh-attarde/llvm-project
that referenced
this pull request
Oct 3, 2025
Fixes llvm#159401 On Windows there is no hex prefix, I suspect because somewhere we print a pointer. I'd prefer to fix that itself but can't get to a Windows machine at the moment. It's not important to the purpose of the test anyway.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
7 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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.