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[lld-macho] Show source information for undefined references 

The error used to look like this:

  ld64.lld: error: undefined symbol: _foo
  >>> referenced by /path/to/bar.o:(symbol _baz+0x4)

If DWARF line information is available, we now show where in the source
the references are coming from:

  ld64.lld: error: unreferenced symbol: _foo
  >>> referenced by: bar.cpp:42 (/path/to/bar.cpp:42)
  >>>                /path/to/bar.o:(symbol _baz+0x4)

Differential Revision: https://reviews.llvm.org/D128184
This commit is contained in:
Daniel Bertalan 2022-06-20 18:49:42 -04:00 committed by Nico Weber
parent 5ba0a9571b
commit cd7624f153
11 changed files with 334 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
lld/ELF/InputFiles.cpp
View File

@ -224,11 +224,11 @@ template <class ELFT>
static std::string getSrcMsgAux(ObjFile<ELFT> &file, const Symbol &sym,
InputSectionBase &sec, uint64_t offset) {
// In DWARF, functions and variables are stored to different places.
// First, lookup a function for a given offset.
// First, look up a function for a given offset.
if (Optional<DILineInfo> info = file.getDILineInfo(&sec, offset))
return createFileLineMsg(info->FileName, info->Line);
// If it failed, lookup again as a variable.
// If it failed, look up again as a variable.
if (Optional<std::pair<std::string, unsigned>> fileLine =
file.getVariableLoc(sym.getName()))
return createFileLineMsg(fileLine->first, fileLine->second);

11
lld/MachO/Dwarf.cpp
View File

@ -20,15 +20,16 @@ using namespace llvm;
std::unique_ptr<DwarfObject> DwarfObject::create(ObjFile *obj) {
auto dObj = std::make_unique<DwarfObject>();
bool hasDwarfInfo = false;
// LLD only needs to extract the source file path from the debug info, so we
// initialize DwarfObject with just the sections necessary to get that path.
// The debugger will locate the debug info via the object file paths that we
// emit in our STABS symbols, so we don't need to process & emit them
// ourselves.
// LLD only needs to extract the source file path and line numbers from the
// debug info, so we initialize DwarfObject with just the sections necessary
// to get that path. The debugger will locate the debug info via the object
// file paths that we emit in our STABS symbols, so we don't need to process &
// emit them ourselves.
for (const InputSection *isec : obj->debugSections) {
if (StringRef *s =
StringSwitch<StringRef *>(isec->getName())
.Case(section_names::debugInfo, &dObj->infoSection.Data)
.Case(section_names::debugLine, &dObj->lineSection.Data)
.Case(section_names::debugAbbrev, &dObj->abbrevSection)
.Case(section_names::debugStr, &dObj->strSection)
.Default(nullptr)) {

5
lld/MachO/Dwarf.h
View File

@ -37,12 +37,17 @@ public:
llvm::StringRef getAbbrevSection() const override { return abbrevSection; }
llvm::StringRef getStrSection() const override { return strSection; }
llvm::DWARFSection const &getLineSection() const override {
return lineSection;
}
// Returns an instance of DwarfObject if the given object file has the
// relevant DWARF debug sections.
static std::unique_ptr<DwarfObject> create(ObjFile *);
private:
llvm::DWARFSection infoSection;
llvm::DWARFSection lineSection;
llvm::StringRef abbrevSection;
llvm::StringRef strSection;
};

27
lld/MachO/InputFiles.cpp
View File

@ -998,6 +998,8 @@ void ObjFile::parseDebugInfo() {
if (!dObj)
return;
// We do not re-use the context from getDwarf() here as that function
// constructs an expensive DWARFCache object.
auto *ctx = make<DWARFContext>(
std::move(dObj), "",
[&](Error err) {
@ -1373,6 +1375,31 @@ void ObjFile::registerEhFrames(Section &ehFrameSection) {
}
}
std::string ObjFile::sourceFile() const {
SmallString<261> dir(compileUnit->getCompilationDir());
StringRef sep = sys::path::get_separator();
// We don't use `path::append` here because we want an empty `dir` to result
// in an absolute path. `append` would give us a relative path for that case.
if (!dir.endswith(sep))
dir += sep;
return (dir + compileUnit->getUnitDIE().getShortName()).str();
}
lld::DWARFCache *ObjFile::getDwarf() {
llvm::call_once(initDwarf, [this]() {
auto dwObj = DwarfObject::create(this);
if (!dwObj)
return;
dwarfCache = std::make_unique<DWARFCache>(std::make_unique<DWARFContext>(
std::move(dwObj), "",
[&](Error err) { warn(getName() + ": " + toString(std::move(err))); },
[&](Error warning) {
warn(getName() + ": " + toString(std::move(warning)));
}));
});
return dwarfCache.get();
}
// The path can point to either a dylib or a .tbd file.
static DylibFile *loadDylib(StringRef path, DylibFile *umbrella) {
Optional<MemoryBufferRef> mbref = readFile(path);

9
lld/MachO/InputFiles.h
View File

@ -12,6 +12,7 @@
#include "MachOStructs.h"
#include "Target.h"
#include "lld/Common/DWARF.h"
#include "lld/Common/LLVM.h"
#include "lld/Common/Memory.h"
#include "llvm/ADT/CachedHashString.h"
@ -21,6 +22,7 @@
#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
#include "llvm/Object/Archive.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Threading.h"
#include "llvm/TextAPI/TextAPIReader.h"
#include <vector>
@ -159,7 +161,13 @@ public:
static bool classof(const InputFile *f) { return f->kind() == ObjKind; }
std::string sourceFile() const;
// Parses line table information for diagnostics. compileUnit should be used
// for other purposes.
lld::DWARFCache *getDwarf();
llvm::DWARFUnit *compileUnit = nullptr;
std::unique_ptr<lld::DWARFCache> dwarfCache;
Section *addrSigSection = nullptr;
const uint32_t modTime;
std::vector<ConcatInputSection *> debugSections;
@ -167,6 +175,7 @@ public:
llvm::DenseMap<ConcatInputSection *, FDE> fdes;
private:
llvm::once_flag initDwarf;
template <class LP> void parseLazy();
template <class SectionHeader> void parseSections(ArrayRef<SectionHeader>);
template <class LP>

64
lld/MachO/InputSection.cpp
View File

@ -55,17 +55,21 @@ static uint64_t resolveSymbolVA(const Symbol *sym, uint8_t type) {
return sym->getVA();
}
const Defined *InputSection::getContainingSymbol(uint64_t off) const {
auto *nextSym = llvm::upper_bound(
symbols, off, [](uint64_t a, const Defined *b) { return a < b->value; });
if (nextSym == symbols.begin())
return nullptr;
return *std::prev(nextSym);
}
std::string InputSection::getLocation(uint64_t off) const {
// First, try to find a symbol that's near the offset. Use it as a reference
// point.
auto *nextSym = llvm::upper_bound(
symbols, off, [](uint64_t a, const Defined *b) { return a < b->value; });
if (nextSym != symbols.begin()) {
auto &sym = *std::prev(nextSym);
if (auto *sym = getContainingSymbol(off))
return (toString(getFile()) + ":(symbol " + sym->getName() + "+0x" +
Twine::utohexstr(off - sym->value) + ")")
.str();
}
// If that fails, use the section itself as a reference point.
for (const Subsection &subsec : section.subsections) {
@ -74,11 +78,61 @@ std::string InputSection::getLocation(uint64_t off) const {
break;
}
}
return (toString(getFile()) + ":(" + getName() + "+0x" +
Twine::utohexstr(off) + ")")
.str();
}
std::string InputSection::getSourceLocation(uint64_t off) const {
auto *obj = dyn_cast<ObjFile>(getFile());
if (!obj)
return {};
DWARFCache *dwarf = obj->getDwarf();
if (!dwarf)
return std::string();
for (const Subsection &subsec : section.subsections) {
if (subsec.isec == this) {
off += subsec.offset;
break;
}
}
auto createMsg = [&](StringRef path, unsigned line) {
std::string filename = sys::path::filename(path).str();
std::string lineStr = (":" + Twine(line)).str();
if (filename == path)
return filename + lineStr;
return (filename + lineStr + " (" + path + lineStr + ")").str();
};
// First, look up a function for a given offset.
if (Optional<DILineInfo> li = dwarf->getDILineInfo(
section.addr + off, object::SectionedAddress::UndefSection))
return createMsg(li->FileName, li->Line);
// If it failed, look up again as a variable.
if (const Defined *sym = getContainingSymbol(off)) {
// Symbols are generally prefixed with an underscore, which is not included
// in the debug information.
StringRef symName = sym->getName();
if (!symName.empty() && symName[0] == '_')
symName = symName.substr(1);
if (Optional<std::pair<std::string, unsigned>> fileLine =
dwarf->getVariableLoc(symName))
return createMsg(fileLine->first, fileLine->second);
}
// Try to get the source file's name from the DWARF information.
if (obj->compileUnit)
return obj->sourceFile();
return {};
}
void ConcatInputSection::foldIdentical(ConcatInputSection *copy) {
align = std::max(align, copy->align);
copy->live = false;

7
lld/MachO/InputSection.h
View File

@ -50,7 +50,11 @@ public:
// The offset from the beginning of the file.
uint64_t getVA(uint64_t off) const;
// Return a user-friendly string for use in diagnostics.
// Format: /path/to/object.o:(symbol _func+0x123)
std::string getLocation(uint64_t off) const;
// Return the source line corresponding to an address, or the empty string.
// Format: Source.cpp:123 (/path/to/Source.cpp:123)
std::string getSourceLocation(uint64_t off) const;
// Whether the data at \p off in this InputSection is live.
virtual bool isLive(uint64_t off) const = 0;
virtual void markLive(uint64_t off) = 0;
@ -85,6 +89,8 @@ public:
protected:
const Section &section;
const Defined *getContainingSymbol(uint64_t off) const;
};
// ConcatInputSections are combined into (Concat)OutputSections through simple
@ -292,6 +298,7 @@ constexpr const char compactUnwind[] = "__compact_unwind";
constexpr const char data[] = "__data";
constexpr const char debugAbbrev[] = "__debug_abbrev";
constexpr const char debugInfo[] = "__debug_info";
constexpr const char debugLine[] = "__debug_line";
constexpr const char debugStr[] = "__debug_str";
constexpr const char ehFrame[] = "__eh_frame";
constexpr const char gccExceptTab[] = "__gcc_except_tab";

7
lld/MachO/SymbolTable.cpp
View File

@ -381,8 +381,11 @@ void macho::reportPendingUndefinedSymbols() {
locations.codeReferences) {
if (i >= maxUndefinedReferences)
break;
// TODO: Get source file/line from debug information.
message += "\n>>> referenced by " + loc.isec->getLocation(loc.offset);
message += "\n>>> referenced by ";
std::string src = loc.isec->getSourceLocation(loc.offset);
if (!src.empty())
message += src + "\n>>> ";
message += loc.isec->getLocation(loc.offset);
++i;
}

13
lld/MachO/SyntheticSections.cpp
View File

@ -834,16 +834,9 @@ SymtabSection::SymtabSection(StringTableSection &stringTableSection)
: LinkEditSection(segment_names::linkEdit, section_names::symbolTable),
stringTableSection(stringTableSection) {}
void SymtabSection::emitBeginSourceStab(DWARFUnit *compileUnit) {
void SymtabSection::emitBeginSourceStab(StringRef sourceFile) {
StabsEntry stab(N_SO);
SmallString<261> dir(compileUnit->getCompilationDir());
StringRef sep = sys::path::get_separator();
// We don't use `path::append` here because we want an empty `dir` to result
// in an absolute path. `append` would give us a relative path for that case.
if (!dir.endswith(sep))
dir += sep;
stab.strx = stringTableSection.addString(
saver().save(dir + compileUnit->getUnitDIE().getShortName()));
stab.strx = stringTableSection.addString(saver().save(sourceFile));
stabs.emplace_back(std::move(stab));
}
@ -938,7 +931,7 @@ void SymtabSection::emitStabs() {
emitEndSourceStab();
lastFile = file;
emitBeginSourceStab(file->compileUnit);
emitBeginSourceStab(file->sourceFile());
emitObjectFileStab(file);
}

2
lld/MachO/SyntheticSections.h
View File

@ -435,7 +435,7 @@ public:
uint32_t getNumUndefinedSymbols() const { return undefinedSymbols.size(); }
private:
void emitBeginSourceStab(llvm::DWARFUnit *compileUnit);
void emitBeginSourceStab(StringRef);
void emitEndSourceStab();
void emitObjectFileStab(ObjFile *);
void emitEndFunStab(Defined *);

210
lld/test/MachO/invalid/undef-debug.s Normal file
View File

@ -0,0 +1,210 @@
# REQUIRES: aarch64
# RUN: llvm-mc -filetype=obj -triple=arm64-apple-macos %s -o %t.o
# RUN: not %lld -arch arm64 %t.o -o /dev/null 2>&1 | FileCheck %s
# CHECK: undefined symbol: _undef
# CHECK-NEXT: >>> referenced by test.c:3
# CHECK-NEXT: >>> {{.*}}.o:(symbol _main+0x0)
# CHECK-NEXT: >>> referenced by test.c:2
# CHECK-NEXT >>> {{.*}}.o:(symbol _ptr+0x0)
## This is the output of `clang -g2 -O2 -fdebug-compilation-dir=. -fno-ident` called on the following file, with the
## Apple DWARF tables removed:
##
## int undef();
## int (*ptr)() = &undef;
## int main() { return undef(); };
.section __TEXT,__text,regular,pure_instructions
.build_version macos, 12, 0 sdk_version 13, 0
.file 1 "." "test.c"
.globl _main ; -- Begin function main
.p2align 2
_main: ; @main
Lfunc_begin0:
.loc 1 3 0 ; test.c:3:0
.cfi_startproc
; %bb.0:
.loc 1 3 21 prologue_end ; test.c:3:21
b _undef
Ltmp0:
Lfunc_end0:
.cfi_endproc
; -- End function
.section __DATA,__data
.globl _ptr ; @ptr
.p2align 3
_ptr:
.quad _undef
.section __DWARF,__debug_abbrev,regular,debug
Lsection_abbrev:
.byte 1 ; Abbreviation Code
.byte 17 ; DW_TAG_compile_unit
.byte 1 ; DW_CHILDREN_yes
.byte 37 ; DW_AT_producer
.byte 14 ; DW_FORM_strp
.byte 19 ; DW_AT_language
.byte 5 ; DW_FORM_data2
.byte 3 ; DW_AT_name
.byte 14 ; DW_FORM_strp
.ascii "\202|" ; DW_AT_LLVM_sysroot
.byte 14 ; DW_FORM_strp
.ascii "\357\177" ; DW_AT_APPLE_sdk
.byte 14 ; DW_FORM_strp
.byte 16 ; DW_AT_stmt_list
.byte 23 ; DW_FORM_sec_offset
.byte 27 ; DW_AT_comp_dir
.byte 14 ; DW_FORM_strp
.ascii "\341\177" ; DW_AT_APPLE_optimized
.byte 25 ; DW_FORM_flag_present
.byte 17 ; DW_AT_low_pc
.byte 1 ; DW_FORM_addr
.byte 18 ; DW_AT_high_pc
.byte 6 ; DW_FORM_data4
.byte 0 ; EOM(1)
.byte 0 ; EOM(2)
.byte 2 ; Abbreviation Code
.byte 52 ; DW_TAG_variable
.byte 0 ; DW_CHILDREN_no
.byte 3 ; DW_AT_name
.byte 14 ; DW_FORM_strp
.byte 73 ; DW_AT_type
.byte 19 ; DW_FORM_ref4
.byte 63 ; DW_AT_external
.byte 25 ; DW_FORM_flag_present
.byte 58 ; DW_AT_decl_file
.byte 11 ; DW_FORM_data1
.byte 59 ; DW_AT_decl_line
.byte 11 ; DW_FORM_data1
.byte 2 ; DW_AT_location
.byte 24 ; DW_FORM_exprloc
.byte 0 ; EOM(1)
.byte 0 ; EOM(2)
.byte 3 ; Abbreviation Code
.byte 15 ; DW_TAG_pointer_type
.byte 0 ; DW_CHILDREN_no
.byte 73 ; DW_AT_type
.byte 19 ; DW_FORM_ref4
.byte 0 ; EOM(1)
.byte 0 ; EOM(2)
.byte 4 ; Abbreviation Code
.byte 21 ; DW_TAG_subroutine_type
.byte 1 ; DW_CHILDREN_yes
.byte 73 ; DW_AT_type
.byte 19 ; DW_FORM_ref4
.byte 0 ; EOM(1)
.byte 0 ; EOM(2)
.byte 5 ; Abbreviation Code
.byte 24 ; DW_TAG_unspecified_parameters
.byte 0 ; DW_CHILDREN_no
.byte 0 ; EOM(1)
.byte 0 ; EOM(2)
.byte 6 ; Abbreviation Code
.byte 36 ; DW_TAG_base_type
.byte 0 ; DW_CHILDREN_no
.byte 3 ; DW_AT_name
.byte 14 ; DW_FORM_strp
.byte 62 ; DW_AT_encoding
.byte 11 ; DW_FORM_data1
.byte 11 ; DW_AT_byte_size
.byte 11 ; DW_FORM_data1
.byte 0 ; EOM(1)
.byte 0 ; EOM(2)
.byte 7 ; Abbreviation Code
.byte 46 ; DW_TAG_subprogram
.byte 0 ; DW_CHILDREN_no
.byte 17 ; DW_AT_low_pc
.byte 1 ; DW_FORM_addr
.byte 18 ; DW_AT_high_pc
.byte 6 ; DW_FORM_data4
.ascii "\347\177" ; DW_AT_APPLE_omit_frame_ptr
.byte 25 ; DW_FORM_flag_present
.byte 64 ; DW_AT_frame_base
.byte 24 ; DW_FORM_exprloc
.byte 3 ; DW_AT_name
.byte 14 ; DW_FORM_strp
.byte 58 ; DW_AT_decl_file
.byte 11 ; DW_FORM_data1
.byte 59 ; DW_AT_decl_line
.byte 11 ; DW_FORM_data1
.byte 73 ; DW_AT_type
.byte 19 ; DW_FORM_ref4
.byte 63 ; DW_AT_external
.byte 25 ; DW_FORM_flag_present
.ascii "\341\177" ; DW_AT_APPLE_optimized
.byte 25 ; DW_FORM_flag_present
.byte 0 ; EOM(1)
.byte 0 ; EOM(2)
.byte 0 ; EOM(3)
.section __DWARF,__debug_info,regular,debug
Lsection_info:
Lcu_begin0:
.set Lset0, Ldebug_info_end0-Ldebug_info_start0 ; Length of Unit
.long Lset0
Ldebug_info_start0:
.short 4 ; DWARF version number
.set Lset1, Lsection_abbrev-Lsection_abbrev ; Offset Into Abbrev. Section
.long Lset1
.byte 8 ; Address Size (in bytes)
.byte 1 ; Abbrev [1] 0xb:0x69 DW_TAG_compile_unit
.long 0 ; DW_AT_producer
.short 12 ; DW_AT_language
.long 1 ; DW_AT_name
.long 8 ; DW_AT_LLVM_sysroot
.long 60 ; DW_AT_APPLE_sdk
.set Lset2, Lline_table_start0-Lsection_line ; DW_AT_stmt_list
.long Lset2
.long 71 ; DW_AT_comp_dir
; DW_AT_APPLE_optimized
.quad Lfunc_begin0 ; DW_AT_low_pc
.set Lset3, Lfunc_end0-Lfunc_begin0 ; DW_AT_high_pc
.long Lset3
.byte 2 ; Abbrev [2] 0x32:0x15 DW_TAG_variable
.long 73 ; DW_AT_name
.long 71 ; DW_AT_type
; DW_AT_external
.byte 1 ; DW_AT_decl_file
.byte 2 ; DW_AT_decl_line
.byte 9 ; DW_AT_location
.byte 3
.quad _ptr
.byte 3 ; Abbrev [3] 0x47:0x5 DW_TAG_pointer_type
.long 76 ; DW_AT_type
.byte 4 ; Abbrev [4] 0x4c:0x7 DW_TAG_subroutine_type
.long 83 ; DW_AT_type
.byte 5 ; Abbrev [5] 0x51:0x1 DW_TAG_unspecified_parameters
.byte 0 ; End Of Children Mark
.byte 6 ; Abbrev [6] 0x53:0x7 DW_TAG_base_type
.long 77 ; DW_AT_name
.byte 5 ; DW_AT_encoding
.byte 4 ; DW_AT_byte_size
.byte 7 ; Abbrev [7] 0x5a:0x19 DW_TAG_subprogram
.quad Lfunc_begin0 ; DW_AT_low_pc
.set Lset4, Lfunc_end0-Lfunc_begin0 ; DW_AT_high_pc
.long Lset4
; DW_AT_APPLE_omit_frame_ptr
.byte 1 ; DW_AT_frame_base
.byte 111
.long 81 ; DW_AT_name
.byte 1 ; DW_AT_decl_file
.byte 3 ; DW_AT_decl_line
.long 83 ; DW_AT_type
; DW_AT_external
; DW_AT_APPLE_optimized
.byte 0 ; End Of Children Mark
Ldebug_info_end0:
.section __DWARF,__debug_str,regular,debug
Linfo_string:
.byte 0 ; string offset=0
.asciz "test.c" ; string offset=1
.asciz "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk" ; string offset=8
.asciz "MacOSX.sdk" ; string offset=60
.asciz "." ; string offset=71
.asciz "ptr" ; string offset=73
.asciz "int" ; string offset=77
.asciz "main" ; string offset=81
.section __DWARF,__debug_line,regular,debug
Lsection_line:
Lline_table_start0: