commit 317b5582b813c51d1fb6723fd44b227b7f274bc7
Author: Hans Wennborg <hans@hanshq.net>
Date:   Fri Oct 7 13:37:28 2022 +0200

    Revert "[lld/mac] Port typo correction for undefined symbols from ELF port"
    
    This caused crashes/assert failures for some Chromium developers, see comment
    on the code review.
    
    > Ports:
    > - core feature: https://reviews.llvm.org/D67039
    > - case mismatch: https://reviews.llvm.org/D70506
    > - extern "C" suggestions: https://reviews.llvm.org/D69592,
    >   https://reviews.llvm.org/D69650
    >
    > Does not port https://reviews.llvm.org/D71735 since I believe that that doesn't
    > apply to lld/Mach-O.
    >
    > Differential Revision: https://reviews.llvm.org/D135038
    
    This reverts commit 8c45e80298f4e3eb6d9cfbafcb099bc087e4668e.

diff --git a/lld/MachO/SymbolTable.cpp b/lld/MachO/SymbolTable.cpp
index ccb1d51bdbe4..5173fa069e22 100644
--- a/lld/MachO/SymbolTable.cpp
+++ b/lld/MachO/SymbolTable.cpp
@@ -392,138 +392,8 @@ void macho::reportPendingDuplicateSymbols() {
   }
 }
 
-// Check whether the definition name def is a mangled function name that matches
-// the reference name ref.
-static bool canSuggestExternCForCXX(StringRef ref, StringRef def) {
-  llvm::ItaniumPartialDemangler d;
-  std::string name = def.str();
-  if (d.partialDemangle(name.c_str()))
-    return false;
-  char *buf = d.getFunctionName(nullptr, nullptr);
-  if (!buf)
-    return false;
-  bool ret = ref == buf;
-  free(buf);
-  return ret;
-}
-
-// Suggest an alternative spelling of an "undefined symbol" diagnostic. Returns
-// the suggested symbol, which is either in the symbol table, or in the same
-// file of sym.
-static const Symbol *getAlternativeSpelling(const Undefined &sym,
-                                            std::string &pre_hint,
-                                            std::string &post_hint) {
-  DenseMap<StringRef, const Symbol *> map;
-  if (sym.getFile() && sym.getFile()->kind() == InputFile::ObjKind) {
-    // Build a map of local defined symbols.
-    for (const Symbol *s : sym.getFile()->symbols)
-      if (auto *defined = dyn_cast<Defined>(s))
-        if (!defined->isExternal())
-          map.try_emplace(s->getName(), s);
-  }
-
-  auto suggest = [&](StringRef newName) -> const Symbol * {
-    // If defined locally.
-    if (const Symbol *s = map.lookup(newName))
-      return s;
-
-    // If in the symbol table and not undefined.
-    if (const Symbol *s = symtab->find(newName))
-      if (dyn_cast<Undefined>(s) == nullptr)
-        return s;
-
-    return nullptr;
-  };
-
-  // This loop enumerates all strings of Levenshtein distance 1 as typo
-  // correction candidates and suggests the one that exists as a non-undefined
-  // symbol.
-  StringRef name = sym.getName();
-  for (size_t i = 0, e = name.size(); i != e + 1; ++i) {
-    // Insert a character before name[i].
-    std::string newName = (name.substr(0, i) + "0" + name.substr(i)).str();
-    for (char c = '0'; c <= 'z'; ++c) {
-      newName[i] = c;
-      if (const Symbol *s = suggest(newName))
-        return s;
-    }
-    if (i == e)
-      break;
-
-    // Substitute name[i].
-    newName = std::string(name);
-    for (char c = '0'; c <= 'z'; ++c) {
-      newName[i] = c;
-      if (const Symbol *s = suggest(newName))
-        return s;
-    }
-
-    // Transpose name[i] and name[i+1]. This is of edit distance 2 but it is
-    // common.
-    if (i + 1 < e) {
-      newName[i] = name[i + 1];
-      newName[i + 1] = name[i];
-      if (const Symbol *s = suggest(newName))
-        return s;
-    }
-
-    // Delete name[i].
-    newName = (name.substr(0, i) + name.substr(i + 1)).str();
-    if (const Symbol *s = suggest(newName))
-      return s;
-  }
-
-  // Case mismatch, e.g. Foo vs FOO.
-  for (auto &it : map)
-    if (name.equals_insensitive(it.first))
-      return it.second;
-  for (Symbol *sym : symtab->getSymbols())
-    if (dyn_cast<Undefined>(sym) == nullptr &&
-        name.equals_insensitive(sym->getName()))
-      return sym;
-
-  // The reference may be a mangled name while the definition is not. Suggest a
-  // missing extern "C".
-  if (name.startswith("__Z")) {
-    std::string buf = name.str();
-    llvm::ItaniumPartialDemangler d;
-    if (!d.partialDemangle(buf.c_str()))
-      if (char *buf = d.getFunctionName(nullptr, nullptr)) {
-        const Symbol *s = suggest((Twine("_") + buf).str());
-        free(buf);
-        if (s) {
-          pre_hint = ": extern \"C\" ";
-          return s;
-        }
-      }
-  } else {
-    StringRef name_without_underscore = name;
-    name_without_underscore.consume_front("_");
-    const Symbol *s = nullptr;
-    for (auto &it : map)
-      if (canSuggestExternCForCXX(name_without_underscore, it.first)) {
-        s = it.second;
-        break;
-      }
-    if (!s)
-      for (Symbol *sym : symtab->getSymbols())
-        if (canSuggestExternCForCXX(name_without_underscore, sym->getName())) {
-          s = sym;
-          break;
-        }
-    if (s) {
-      pre_hint = " to declare ";
-      post_hint = " as extern \"C\"?";
-      return s;
-    }
-  }
-
-  return nullptr;
-}
-
 static void reportUndefinedSymbol(const Undefined &sym,
-                                  const UndefinedDiag &locations,
-                                  bool correctSpelling) {
+                                  const UndefinedDiag &locations) {
   std::string message = "undefined symbol";
   if (config->archMultiple)
     message += (" for arch " + getArchitectureName(config->arch())).str();
@@ -556,17 +426,6 @@ static void reportUndefinedSymbol(const Undefined &sym,
         ("\n>>> referenced " + Twine(totalReferences - i) + " more times")
             .str();
 
-  if (correctSpelling) {
-    std::string pre_hint = ": ", post_hint;
-    if (const Symbol *corrected =
-            getAlternativeSpelling(sym, pre_hint, post_hint)) {
-      message +=
-          "\n>>> did you mean" + pre_hint + toString(*corrected) + post_hint;
-      if (corrected->getFile())
-        message += "\n>>> defined in: " + toString(corrected->getFile());
-    }
-  }
-
   if (config->undefinedSymbolTreatment == UndefinedSymbolTreatment::error)
     error(message);
   else if (config->undefinedSymbolTreatment ==
@@ -577,9 +436,8 @@ static void reportUndefinedSymbol(const Undefined &sym,
 }
 
 void macho::reportPendingUndefinedSymbols() {
-  // Enable spell corrector for the first 2 diagnostics.
-  for (const auto &[i, undef] : llvm::enumerate(undefs))
-    reportUndefinedSymbol(*undef.first, undef.second, i < 2);
+  for (const auto &undef : undefs)
+    reportUndefinedSymbol(*undef.first, undef.second);
 
   // This function is called multiple times during execution. Clear the printed
   // diagnostics to avoid printing the same things again the next time.
diff --git a/lld/test/MachO/undef-spell-corrector.s b/lld/test/MachO/undef-spell-corrector.s
deleted file mode 100644
index cfec062bfb53..000000000000
--- a/lld/test/MachO/undef-spell-corrector.s
+++ /dev/null
@@ -1,79 +0,0 @@
-# REQUIRES: x86
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos %s -o %t.o
-
-## Insert a character.
-## The spell corrector is enabled for the first two "undefined symbol" diagnostics.
-# RUN: echo 'call bcde; call abcd; call abde' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=INSERT %s -DFILE=%t.o
-
-## Symbols defined in DSO can be suggested.
-# RUN: %lld %t.o -dylib -o %t.dylib
-# RUN: not %lld %t.dylib %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=INSERT %s -DFILE=%t.dylib
-
-# INSERT:      error: undefined symbol: abde
-# INSERT-NEXT: >>> referenced by {{.*}}
-# INSERT-NEXT: >>> did you mean: abcde
-# INSERT-NEXT: >>> defined in: [[FILE]]
-# INSERT:      error: undefined symbol: abcd
-# INSERT-NEXT: >>> referenced by {{.*}}
-# INSERT-NEXT: >>> did you mean: abcde
-# INSERT-NEXT: >>> defined in: [[FILE]]
-# INSERT:      error: undefined symbol: bcde
-# INSERT-NEXT: >>> referenced by {{.*}}
-# INSERT-NOT:  >>>
-
-## Substitute a character.
-# RUN: echo 'call bbcde; call abcdd' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=SUBST %s
-
-# SUBST:      error: undefined symbol: abcdd
-# SUBST-NEXT: >>> referenced by {{.*}}
-# SUBST-NEXT: >>> did you mean: abcde
-# SUBST:      error: undefined symbol: bbcde
-# SUBST-NEXT: >>> referenced by {{.*}}
-# SUBST-NEXT: >>> did you mean: abcde
-
-## Delete a character.
-# RUN: echo 'call aabcde; call abcdee' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=DELETE %s
-
-# DELETE:      error: undefined symbol: abcdee
-# DELETE-NEXT: >>> referenced by {{.*}}
-# DELETE-NEXT: >>> did you mean: abcde
-# DELETE:      error: undefined symbol: aabcde
-# DELETE-NEXT: >>> referenced by {{.*}}
-# DELETE-NEXT: >>> did you mean: abcde
-
-## Transpose.
-# RUN: echo 'call bacde' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=TRANSPOSE %s
-
-# TRANSPOSE:      error: undefined symbol: bacde
-# TRANSPOSE-NEXT: >>> referenced by {{.*}}
-# TRANSPOSE-NEXT: >>> did you mean: abcde
-
-## Missing const qualifier.
-# RUN: echo 'call __Z3fooPi' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -demangle -o /dev/null 2>&1 | FileCheck --check-prefix=CONST %s
-## Local defined symbols.
-# RUN: echo '__Z3fooPKi: call __Z3fooPi' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t1.o -demangle -o /dev/null 2>&1 | FileCheck --check-prefix=CONST %s
-
-# CONST:      error: undefined symbol: foo(int*)
-# CONST-NEXT: >>> referenced by {{.*}}
-# CONST-NEXT: >>> did you mean: foo(int const*)
-
-## Case mismatch.
-# RUN: echo 'call __Z3FOOPKi' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -demangle -o /dev/null 2>&1 | FileCheck --check-prefix=CASE %s
-# RUN: echo '__Z3fooPKi: call __Z3FOOPKi' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t1.o -demangle -o /dev/null 2>&1 | FileCheck --check-prefix=CASE %s
-
-# CASE:      error: undefined symbol: FOO(int const*)
-# CASE-NEXT: >>> referenced by {{.*}}
-# CASE-NEXT: >>> did you mean: foo(int const*)
-
-.globl _main, abcde, __Z3fooPKi
-_main:
-abcde:
-__Z3fooPKi:
diff --git a/lld/test/MachO/undef-suggest-extern-c.s b/lld/test/MachO/undef-suggest-extern-c.s
deleted file mode 100644
index 8c53c8e602ca..000000000000
--- a/lld/test/MachO/undef-suggest-extern-c.s
+++ /dev/null
@@ -1,19 +0,0 @@
-# REQUIRES: x86
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos %s -o %t.o
-
-## The reference is mangled while the definition is not, suggest a missing
-## extern "C".
-# RUN: echo 'call __Z3fooi' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -demangle -o /dev/null 2>&1 | FileCheck %s
-
-# CHECK:      error: undefined symbol: foo(int)
-# CHECK-NEXT: >>> referenced by {{.*}}
-# CHECK-NEXT: >>> did you mean: extern "C" foo
-
-## Don't suggest for nested names like F::foo() and foo::foo().
-# RUN: echo 'call __ZN1F3fooEv; call __ZN3fooC1Ev' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t2.o
-# RUN: not ld.lld %t.o %t2.o -o /dev/null 2>&1 | FileCheck /dev/null --implicit-check-not='did you mean'
-
-.globl _start, _foo
-_start:
-_foo:
diff --git a/lld/test/MachO/undef-suggest-extern-c2.s b/lld/test/MachO/undef-suggest-extern-c2.s
deleted file mode 100644
index 152fe3877e2d..000000000000
--- a/lld/test/MachO/undef-suggest-extern-c2.s
+++ /dev/null
@@ -1,21 +0,0 @@
-# REQUIRES: x86
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos %s -o %t.o
-
-## The definition is mangled while the reference is not, suggest an arbitrary
-## C++ overload.
-# RUN: echo '.globl __Z3fooi; __Z3fooi:' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t1.o
-# RUN: not %lld %t.o %t1.o -demangle -o /dev/null 2>&1 | FileCheck %s
-
-## Check that we can suggest a local definition.
-# RUN: echo '__Z3fooi: call _foo' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t2.o
-# RUN: not %lld %t2.o -demangle -o /dev/null 2>&1 | FileCheck %s
-
-# CHECK:      error: undefined symbol: foo
-# CHECK-NEXT: >>> referenced by {{.*}}
-# CHECK-NEXT: >>> did you mean to declare foo(int) as extern "C"?
-
-## Don't suggest nested names whose base name is "foo", e.g. F::foo().
-# RUN: echo '.globl __ZN1F3fooEv; __ZN1F3fooEv:' | llvm-mc -filetype=obj -triple=x86_64-apple-macos - -o %t3.o
-# RUN: not %lld %t.o %t3.o -o /dev/null 2>&1 | FileCheck /dev/null --implicit-check-not='did you mean'
-
-call _foo