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llvm-gsymutil now handles empty linkage names correctly. (#68931)
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Previous to this fix, if we had a DW_TAG_subprogram that had a
DW_AT_linkage_name that was empty, it would attempt to use this name
which would cause an error to be emitted when saving the gsym file to
disk:

error: DWARF conversion failed: : attempted to encode invalid
FunctionInfo object

This patch fixes this issue and adds a unit test case.
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@clayborg
clayborg committed Oct 16, 2023
1 parent 910a4bf commit 78be6b2
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Showing 2 changed files with 157 additions and 5 deletions.
10 changes: 5 additions & 5 deletions llvm/lib/DebugInfo/GSYM/DwarfTransformer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -132,11 +132,11 @@ static DWARFDie GetParentDeclContextDIE(DWARFDie &Die) {
static std::optional<uint32_t>
getQualifiedNameIndex(DWARFDie &Die, uint64_t Language, GsymCreator &Gsym) {
// If the dwarf has mangled name, use mangled name
if (auto LinkageName =
dwarf::toString(Die.findRecursively({dwarf::DW_AT_MIPS_linkage_name,
dwarf::DW_AT_linkage_name}),
nullptr))
return Gsym.insertString(LinkageName, /* Copy */ false);
if (auto LinkageName = Die.getLinkageName()) {
// We have seen cases were linkage name is actually empty.
if (strlen(LinkageName) > 0)
return Gsym.insertString(LinkageName, /* Copy */ false);
}

StringRef ShortName(Die.getName(DINameKind::ShortName));
if (ShortName.empty())
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152 changes: 152 additions & 0 deletions llvm/unittests/DebugInfo/GSYM/GSYMTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4005,3 +4005,155 @@ TEST(GSYMTest, TestEmptyRangeWarnings) {
// Make sure we don't see spurious errors in the output:
EXPECT_TRUE(errors.find("error:") == std::string::npos);
}


TEST(GSYMTest, TestEmptyLinkageName) {
// This example has a single compile unit that has a DW_TAG_subprogram that
// has a function that has an empty linkage name and a valid normal name.
// Previously this would cause an encoding error:
//
// DWARF conversion failed: attempted to encode invalid FunctionInfo object
//
// This was because we would get a valid but empty linkage name and we would
// try to use this in the GSYM FunctionInfo and that would cause the error
// as the name was empty.
//
// 0x0000000b: DW_TAG_compile_unit
// DW_AT_name ("/tmp/main.cpp")
// DW_AT_language (DW_LANG_C)
// DW_AT_stmt_list (0x00000000)
//
// 0x00000015: DW_TAG_subprogram
// DW_AT_name ("foo")
// DW_AT_linkage_name ("")
// DW_AT_low_pc (0x0000000000001000)
// DW_AT_high_pc (0x0000000000001050)
//
// 0x0000002e: NULL


StringRef yamldata = R"(
debug_str:
- ''
- '/tmp/main.cpp'
- foo
- ''
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
- Attribute: DW_AT_stmt_list
Form: DW_FORM_sec_offset
- Code: 0x2
Tag: DW_TAG_subprogram
Children: DW_CHILDREN_no
Attributes:
- Attribute: DW_AT_name
Form: DW_FORM_strp
- Attribute: DW_AT_linkage_name
Form: DW_FORM_strp
- Attribute: DW_AT_low_pc
Form: DW_FORM_addr
- Attribute: DW_AT_high_pc
Form: DW_FORM_addr
debug_info:
- Length: 0x2B
Version: 4
AbbrevTableID: 0
AbbrOffset: 0x0
AddrSize: 8
Entries:
- AbbrCode: 0x1
Values:
- Value: 0x1
- Value: 0x2
- Value: 0x0
- AbbrCode: 0x2
Values:
- Value: 0xF
- Value: 0x13
- Value: 0x1000
- Value: 0x1050
- AbbrCode: 0x0
debug_line:
- Length: 68
Version: 2
PrologueLength: 36
MinInstLength: 1
DefaultIsStmt: 1
LineBase: 251
LineRange: 14
OpcodeBase: 13
StandardOpcodeLengths: [ 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1 ]
IncludeDirs:
- '/tmp'
Files:
- Name: main.cpp
DirIdx: 1
ModTime: 0
Length: 0
Opcodes:
- Opcode: DW_LNS_extended_op
ExtLen: 9
SubOpcode: DW_LNE_set_address
Data: 4096
- Opcode: DW_LNS_advance_line
SData: 9
Data: 0
- Opcode: DW_LNS_copy
Data: 0
- Opcode: DW_LNS_advance_pc
Data: 256
- Opcode: DW_LNS_advance_line
SData: 1
Data: 0
- Opcode: DW_LNS_copy
Data: 0
- Opcode: DW_LNS_advance_pc
Data: 256
- Opcode: DW_LNS_extended_op
ExtLen: 1
SubOpcode: DW_LNE_end_sequence
Data: 0
)";
auto ErrOrSections = DWARFYAML::emitDebugSections(yamldata);
ASSERT_THAT_EXPECTED(ErrOrSections, Succeeded());
std::unique_ptr<DWARFContext> DwarfContext =
DWARFContext::create(*ErrOrSections, 8);
ASSERT_TRUE(DwarfContext.get() != nullptr);
std::string errors;
raw_string_ostream OS(errors);
GsymCreator GC;
DwarfTransformer DT(*DwarfContext, GC);
const uint32_t ThreadCount = 1;
ASSERT_THAT_ERROR(DT.convert(ThreadCount, &OS), Succeeded());
ASSERT_THAT_ERROR(GC.finalize(OS), Succeeded());
OS.flush();
SmallString<512> Str;
raw_svector_ostream OutStrm(Str);
const auto ByteOrder = llvm::endianness::native;
FileWriter FW(OutStrm, ByteOrder);
ASSERT_THAT_ERROR(GC.encode(FW), Succeeded());
Expected<GsymReader> GR = GsymReader::copyBuffer(OutStrm.str());
ASSERT_THAT_EXPECTED(GR, Succeeded());
// There should be one function in our GSYM.
EXPECT_EQ(GR->getNumAddresses(), 1u);
// Verify "foo" is present and has a line table and no inline info.
auto ExpFI = GR->getFunctionInfo(0x1000);
ASSERT_THAT_EXPECTED(ExpFI, Succeeded());
ASSERT_EQ(ExpFI->Range, AddressRange(0x1000, 0x1050));
EXPECT_TRUE(ExpFI->OptLineTable.has_value());
EXPECT_FALSE(ExpFI->Inline.has_value());
StringRef FuncName = GR->getString(ExpFI->Name);
EXPECT_EQ(FuncName, "foo");

// Make sure we don't see spurious errors in the output:
EXPECT_TRUE(errors.find("error:") == std::string::npos);
}

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