https://github.com/Michael137 created
https://github.com/llvm/llvm-project/pull/145328
`DWARFFormValue::ExtractValue` has nothing to extract for
`DW_FORM_implicit_const` since the value is stored in the abbreviation.
`DWARFFormValue` expects the user to have set the value of the implicit_const.
This patch does so in `GetAttributeValue`.
>From 77e83f6b3257c9cd387b773dc86c4ca8e23051b5 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuc...@gmail.com>
Date: Mon, 23 Jun 2025 14:19:16 +0100
Subject: [PATCH] [lldb][DWARF] Support retrieving DW_FORM_implicit_const value
with DWARFDebugInfoEntry::GetAttributeValue
`DWARFFormValue::ExtractValue` has nothing to extract for
`DW_FORM_implicit_const` since the value is stored in the abbreviation.
`DWARFFormValue` expects the user to have set the value of the
implicit_const. This patch does so in `GetAttributeValue`.
---
.../SymbolFile/DWARF/DWARFDebugInfoEntry.cpp | 3 +
.../SymbolFile/DWARF/DWARFDIETest.cpp | 58 +++++++++++++++++++
2 files changed, 61 insertions(+)
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp
b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp
index 8217c85f86014..13b68e747b1ce 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp
@@ -403,6 +403,9 @@ dw_offset_t DWARFDebugInfoEntry::GetAttributeValue(
const dw_offset_t attr_offset = offset;
form_value.SetUnit(cu);
form_value.SetForm(abbrevDecl->getFormByIndex(idx));
+ if (abbrevDecl->getAttrIsImplicitConstByIndex(idx))
+ form_value.SetValue(abbrevDecl->getAttrImplicitConstValueByIndex(idx));
+
if (form_value.ExtractValue(data, &offset)) {
if (end_attr_offset_ptr)
*end_attr_offset_ptr = offset;
diff --git a/lldb/unittests/SymbolFile/DWARF/DWARFDIETest.cpp
b/lldb/unittests/SymbolFile/DWARF/DWARFDIETest.cpp
index 3f61d1607073c..0da26d99ad383 100644
--- a/lldb/unittests/SymbolFile/DWARF/DWARFDIETest.cpp
+++ b/lldb/unittests/SymbolFile/DWARF/DWARFDIETest.cpp
@@ -395,6 +395,64 @@ TEST(DWARFDIETest, GetContextInFunction) {
testing::ElementsAre(make_struct("struct_t")));
}
+TEST(DWARFDIETest, GetAttributeValue_ImplicitConst) {
+ // Make sure we can correctly retrieve the value of an attribute
+ // that has a DW_FORM_implicit_const form.
+
+ const char *yamldata = R"(
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_EXEC
+ Machine: EM_386
+DWARF:
+ debug_str:
+ - ''
+ debug_abbrev:
+ - ID: 0
+ Table:
+ - Code: 0x1
+ Tag: DW_TAG_compile_unit
+ Children: DW_CHILDREN_yes
+ - Code: 0x2
+ Tag: DW_TAG_subprogram
+ Children: DW_CHILDREN_no
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_string
+ - Attribute: DW_AT_object_pointer
+ Form: DW_FORM_implicit_const
+ Value: 5
+ debug_info:
+ - Version: 5
+ UnitType: DW_UT_compile
+ AddrSize: 8
+ Entries:
+ - AbbrCode: 0x1
+ - AbbrCode: 0x2
+ Values:
+ - Value: 0xDEADBEEFDEADBEEF
+ CStr: func
+ - AbbrCode: 0x0)";
+
+ YAMLModuleTester t(yamldata);
+ auto *symbol_file =
+ llvm::cast<SymbolFileDWARF>(t.GetModule()->GetSymbolFile());
+ DWARFUnit *unit = symbol_file->DebugInfo().GetUnitAtIndex(0);
+ ASSERT_TRUE(unit);
+
+ DWARFDIE subprogram = unit->DIE().GetFirstChild();
+ ASSERT_TRUE(subprogram);
+ dw_offset_t end_attr_offset;
+ DWARFFormValue form_value;
+ dw_offset_t offset = subprogram.GetDIE()->GetAttributeValue(
+ unit, DW_AT_object_pointer, form_value, &end_attr_offset);
+ EXPECT_EQ(form_value.Unsigned(), 5U);
+ EXPECT_GT(offset, 0U);
+ EXPECT_GT(end_attr_offset, 0U);
+}
+
struct GetAttributesTestFixture : public testing::TestWithParam<dw_attr_t> {};
TEST_P(GetAttributesTestFixture, TestGetAttributes_IterationOrder) {
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