Revert "[lld-macho] Add basic symbol table output"

This reverts commit a3d95a50ee.

Reverting due to UBSan failures:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/40817/steps/check-lld%20ubsan/logs/stdio

lld/MachO/SyntheticSections.cpp

@@ -9,7 +9,6 @@
 #include "SyntheticSections.h"
 #include "InputFiles.h"
 #include "OutputSegment.h"
-#include "SymbolTable.h"
 #include "Symbols.h"
 #include "Writer.h"
 
@@ -129,59 +128,6 @@ void BindingSection::writeTo(uint8_t *buf) {
   memcpy(buf, contents.data(), contents.size());
 }
 
-SymtabSection::SymtabSection(StringTableSection &stringTableSection)
-    : stringTableSection(stringTableSection) {
-  segname = segment_names::linkEdit;
-  name = section_names::symbolTable;
-}
-
-size_t SymtabSection::getSize() const {
-  return symbols.size() * sizeof(nlist_64);
-}
-
-void SymtabSection::finalizeContents() {
-  // TODO: We should filter out some symbols.
-  for (Symbol *sym : symtab->getSymbols())
-    symbols.push_back({sym, stringTableSection.addString(sym->getName())});
-}
-
-void SymtabSection::writeTo(uint8_t *buf) {
-  auto *nList = reinterpret_cast<nlist_64 *>(buf);
-  for (const SymtabEntry &entry : symbols) {
-    // TODO support other symbol types
-    // TODO populate n_desc
-    if (auto defined = dyn_cast<Defined>(entry.sym)) {
-      nList->n_strx = entry.strx;
-      nList->n_type = N_EXT | N_SECT;
-      nList->n_sect = defined->isec->sectionIndex;
-      // For the N_SECT symbol type, n_value is the address of the symbol
-      nList->n_value = defined->value + defined->isec->addr;
-    }
-
-    ++nList;
-  }
-}
-
-StringTableSection::StringTableSection() {
-  segname = segment_names::linkEdit;
-  name = section_names::stringTable;
-}
-
-uint32_t StringTableSection::addString(StringRef str) {
-  uint32_t strx = size;
-  strings.push_back(str);
-  size += str.size() + 1; // account for null terminator
-  return strx;
-}
-
-void StringTableSection::writeTo(uint8_t *buf) {
-  uint32_t off = 0;
-  for (StringRef str : strings) {
-    memcpy(buf + off, str.data(), str.size());
-    off += str.size() + 1; // account for null terminator
-  }
-}
-
 InStruct in;
 
 } // namespace macho

lld/MachO/SyntheticSections.h

@@ -23,8 +23,6 @@ namespace section_names {
 constexpr const char *pageZero = "__pagezero";
 constexpr const char *header = "__mach_header";
 constexpr const char *binding = "__binding";
-constexpr const char *symbolTable = "__symbol_table";
-constexpr const char *stringTable = "__string_table";
 
 } // namespace section_names
 
@@ -95,49 +93,6 @@ public:
   SmallVector<char, 128> contents;
 };
 
-// Stores the strings referenced by the symbol table.
-class StringTableSection : public InputSection {
-public:
-  StringTableSection();
-  // Returns the start offset of the added string.
-  uint32_t addString(StringRef);
-  size_t getSize() const override { return size; }
-  // Like other sections in __LINKEDIT, the string table section is special: its
-  // offsets are recorded in the LC_SYMTAB load command, instead of in section
-  // headers.
-  bool isHidden() const override { return true; }
-  void writeTo(uint8_t *buf) override;
-
-private:
-  // An n_strx value of 0 always indicates the empty string, so we must locate
-  // our non-empty string values at positive offsets in the string table.
-  // Therefore we insert a dummy value at position zero.
-  std::vector<StringRef> strings{"\0"};
-  size_t size = 1;
-};
-
-struct SymtabEntry {
-  Symbol *sym;
-  size_t strx;
-};
-
-class SymtabSection : public InputSection {
-public:
-  SymtabSection(StringTableSection &);
-  void finalizeContents();
-  size_t getNumSymbols() const { return symbols.size(); }
-  size_t getSize() const override;
-  // Like other sections in __LINKEDIT, the symtab section is special: its
-  // offsets are recorded in the LC_SYMTAB load command, instead of in section
-  // headers.
-  bool isHidden() const override { return true; }
-  void writeTo(uint8_t *buf) override;
-
-private:
-  StringTableSection &stringTableSection;
-  std::vector<SymtabEntry> symbols;
-};
-
 struct InStruct {
   GotSection *got = nullptr;
 };

lld/MachO/Writer.cpp

@@ -52,8 +52,6 @@ public:
   uint64_t fileOff = 0;
   MachHeaderSection *headerSection = nullptr;
   BindingSection *bindingSection = nullptr;
-  SymtabSection *symtabSection = nullptr;
-  StringTableSection *stringTableSection = nullptr;
 };
 
 // LC_DYLD_INFO_ONLY stores the offsets of symbol import/export information.
@@ -165,23 +163,13 @@ class LCMain : public LoadCommand {
 
 class LCSymtab : public LoadCommand {
 public:
-  LCSymtab(SymtabSection *symtabSection, StringTableSection *stringTableSection)
-      : symtabSection(symtabSection), stringTableSection(stringTableSection) {}
-
   uint32_t getSize() const override { return sizeof(symtab_command); }
 
   void writeTo(uint8_t *buf) const override {
     auto *c = reinterpret_cast<symtab_command *>(buf);
     c->cmd = LC_SYMTAB;
     c->cmdsize = getSize();
-    c->symoff = symtabSection->getFileOffset();
-    c->nsyms = symtabSection->getNumSymbols();
-    c->stroff = stringTableSection->getFileOffset();
-    c->strsize = stringTableSection->getFileSize();
   }
-
-  SymtabSection *symtabSection = nullptr;
-  StringTableSection *stringTableSection = nullptr;
 };
 
 class LCLoadDylib : public LoadCommand {
@@ -250,12 +238,7 @@ public:
         {defaultPosition, {}},
         // Make sure __LINKEDIT is the last segment (i.e. all its hidden
         // sections must be ordered after other sections).
-        {segment_names::linkEdit,
-         {
-             section_names::binding,
-             section_names::symbolTable,
-             section_names::stringTable,
-         }},
+        {segment_names::linkEdit, {section_names::binding}},
     };
 
     for (uint32_t i = 0, n = ordering.size(); i < n; ++i) {
@@ -311,8 +294,7 @@ void Writer::scanRelocations() {
 void Writer::createLoadCommands() {
   headerSection->addLoadCommand(make<LCDyldInfo>(bindingSection));
   headerSection->addLoadCommand(make<LCLoadDylinker>());
-  headerSection->addLoadCommand(
-      make<LCSymtab>(symtabSection, stringTableSection));
+  headerSection->addLoadCommand(make<LCSymtab>());
   headerSection->addLoadCommand(make<LCDysymtab>());
   headerSection->addLoadCommand(make<LCMain>());
 
@@ -341,8 +323,6 @@ void Writer::createLoadCommands() {
 void Writer::createHiddenSections() {
   headerSection = createInputSection<MachHeaderSection>();
   bindingSection = createInputSection<BindingSection>();
-  stringTableSection = createInputSection<StringTableSection>();
-  symtabSection = createInputSection<SymtabSection>(*stringTableSection);
   createInputSection<PageZeroSection>();
 }
 
@@ -425,7 +405,6 @@ void Writer::run() {
 
   // Fill __LINKEDIT contents.
   bindingSection->finalizeContents();
-  symtabSection->finalizeContents();
 
   // Now that __LINKEDIT is filled out, do a proper calculation of its
   // addresses and offsets. We don't have to recalculate the other segments

lld/test/MachO/symtab.s

@@ -1,54 +0,0 @@
-# REQUIRES: x86
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
-# RUN: lld -flavor darwinnew -o %t %t.o
-# RUN: llvm-readobj -symbols %t | FileCheck %s
-
-# CHECK:      Symbols [
-# CHECK-NEXT:   Symbol {
-# CHECK-NEXT:     Name: _main
-# CHECK-NEXT:     Extern
-# CHECK-NEXT:     Type: Section (0xE)
-# CHECK-NEXT:     Section: __text (0x1)
-# CHECK-NEXT:     RefType:
-# CHECK-NEXT:     Flags [ (0x0)
-# CHECK-NEXT:     ]
-# CHECK-NEXT:     Value:
-# CHECK-NEXT:   }
-# CHECK-NEXT:   Symbol {
-# CHECK-NEXT:     Name: bar
-# CHECK-NEXT:     Extern
-# CHECK-NEXT:     Type: Section (0xE)
-# CHECK-NEXT:     Section: __text (0x1)
-# CHECK-NEXT:     RefType:
-# CHECK-NEXT:     Flags [ (0x0)
-# CHECK-NEXT:     ]
-# CHECK-NEXT:     Value:
-# CHECK-NEXT:   }
-# CHECK-NEXT:   Symbol {
-# CHECK-NEXT:     Name: foo
-# CHECK-NEXT:     Extern
-# CHECK-NEXT:     Type: Section (0xE)
-# CHECK-NEXT:     Section: __data
-# CHECK-NEXT:     RefType:
-# CHECK-NEXT:     Flags [ (0x0)
-# CHECK-NEXT:     ]
-# CHECK-NEXT:     Value:
-# CHECK-NEXT:   }
-# CHECK-NEXT: ]
-
-.data
-.global foo
-foo:
-  .asciz "Hello world!\n"
-
-.text
-.global bar
-.global _main
-
-_main:
-  mov $0, %rax
-  ret
-
-bar:
-  mov $2, %rax
-  ret