Thread Expected<...> up from libObject’s getName() for symbols to allow llvm-objdump to produce a good error message.

Produce another specific error message for a malformed Mach-O file when a symbol’s
string index is past the end of the string table.  The existing test case in test/Object/macho-invalid.test
for macho-invalid-symbol-name-past-eof now reports the error with the message indicating
that a symbol at a specific index has a bad sting index and that bad string index value.
 
Again converting interfaces to Expected<> from ErrorOr<> does involve
touching a number of places. Where the existing code reported the error with a
string message or an error code it was converted to do the same.  There is some
code for this that could be factored into a routine but I would like to leave that for
the code owners post-commit to do as they want for handling an llvm::Error.  An
example of how this could be done is shown in the diff in
lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h which had a Check() routine
already for std::error_code so I added one like it for llvm::Error .

Also there some were bugs in the existing code that did not deal with the
old ErrorOr<> return values.  So now with Expected<> since they must be
checked and the error handled, I added a TODO and a comment:
“// TODO: Actually report errors helpfully” and a call something like
consumeError(NameOrErr.takeError()) so the buggy code will not crash
since needed to deal with the Error.

Note there fixes needed to lld that goes along with this that I will commit right after this.
So expect lld not to built after this commit and before the next one.

llvm-svn: 266919

1 files changed, 21 insertions, 6 deletions

diff --git a/llvm/lib/Object/MachOObjectFile.cpp b/llvm/lib/Object/MachOObjectFile.cpp
index deb7f9cece3..41c9a5239a6 100644
--- a/llvm/lib/Object/MachOObjectFile.cpp
+++ b/llvm/lib/Object/MachOObjectFile.cpp
@@ -46,12 +46,11 @@ malformedError(std::string FileName, std::string Msg,
                                         ECOverride);
 }
 
-
 // FIXME: Remove ECOverride once Error has been plumbed down to obj tool code.
 static Error
-malformedError(const MachOObjectFile &Obj, std::string Msg,
+malformedError(const MachOObjectFile &Obj, Twine Msg,
                object_error ECOverride = object_error::parse_failed) {
-  return malformedError(Obj.getFileName(), std::move(Msg), ECOverride);
+  return malformedError(Obj.getFileName(), std::move(Msg.str()), ECOverride);
 }
 
 // FIXME: Replace all uses of this function with getStructOrErr.
@@ -444,12 +443,16 @@ void MachOObjectFile::moveSymbolNext(DataRefImpl &Symb) const {
   Symb.p += SymbolTableEntrySize;
 }
 
-ErrorOr<StringRef> MachOObjectFile::getSymbolName(DataRefImpl Symb) const {
+Expected<StringRef> MachOObjectFile::getSymbolName(DataRefImpl Symb) const {
   StringRef StringTable = getStringTableData();
   MachO::nlist_base Entry = getSymbolTableEntryBase(this, Symb);
   const char *Start = &StringTable.data()[Entry.n_strx];
-  if (Start < getData().begin() || Start >= getData().end())
-    return object_error::parse_failed;
+  if (Start < getData().begin() || Start >= getData().end()) {
+    return malformedError(*this, Twine("truncated or malformed object (bad "
+                          "string index: ") + Twine(Entry.n_strx) + Twine(" for "
+                          "symbol at index ") + Twine(getSymbolIndex(Symb)) +
+                          Twine(")"));
+  }
   return StringRef(Start);
 }
 
@@ -1108,6 +1111,18 @@ basic_symbol_iterator MachOObjectFile::getSymbolByIndex(unsigned Index) const {
   return basic_symbol_iterator(SymbolRef(DRI, this));
 }
 
+uint64_t MachOObjectFile::getSymbolIndex(DataRefImpl Symb) const {
+  MachO::symtab_command Symtab = getSymtabLoadCommand();
+  if (!SymtabLoadCmd)
+    report_fatal_error("getSymbolIndex() called with no symbol table symbol");
+  unsigned SymbolTableEntrySize =
+    is64Bit() ? sizeof(MachO::nlist_64) : sizeof(MachO::nlist);
+  DataRefImpl DRIstart;
+  DRIstart.p = reinterpret_cast<uintptr_t>(getPtr(this, Symtab.symoff));
+  uint64_t Index = (Symb.p - DRIstart.p) / SymbolTableEntrySize;
+  return Index;
+}
+
 section_iterator MachOObjectFile::section_begin() const {
   DataRefImpl DRI;
   return section_iterator(SectionRef(DRI, this));