Update MachOObjectFile::getSymbolAddress so it returns UnknownAddressOrSize
for undefined symbols, so it matches what COFFObjectFile::getSymbolAddress
does.  This allows llvm-nm to print spaces instead of 0’s for the value
of undefined symbols in Mach-O files.

To make this change other uses of MachOObjectFile::getSymbolAddress
are updated to handle when the Value is returned as UnknownAddressOrSize.
Which is needed to keep two of the ExecutionEngine tests working for example.

llvm-svn: 209253
diff --git a/llvm/lib/Object/MachOObjectFile.cpp b/llvm/lib/Object/MachOObjectFile.cpp
index 0951460..c6bab03 100644
--- a/llvm/lib/Object/MachOObjectFile.cpp
+++ b/llvm/lib/Object/MachOObjectFile.cpp
@@ -472,10 +472,18 @@
                                              uint64_t &Res) const {
   if (is64Bit()) {
     MachO::nlist_64 Entry = getSymbol64TableEntry(Symb);
-    Res = Entry.n_value;
+    if ((Entry.n_type & MachO::N_TYPE) == MachO::N_UNDF &&
+        Entry.n_value == 0)
+      Res = UnknownAddressOrSize;
+    else
+      Res = Entry.n_value;
   } else {
     MachO::nlist Entry = getSymbolTableEntry(Symb);
-    Res = Entry.n_value;
+    if ((Entry.n_type & MachO::N_TYPE) == MachO::N_UNDF &&
+        Entry.n_value == 0)
+      Res = UnknownAddressOrSize;
+    else
+      Res = Entry.n_value;
   }
   return object_error::success;
 }
@@ -501,6 +509,10 @@
   nlist_base Entry = getSymbolTableEntryBase(this, DRI);
   uint64_t Value;
   getSymbolAddress(DRI, Value);
+  if (Value == UnknownAddressOrSize) {
+    Result = UnknownAddressOrSize;
+    return object_error::success;
+  }
 
   BeginOffset = Value;
 
@@ -519,6 +531,8 @@
     DataRefImpl DRI = Symbol.getRawDataRefImpl();
     Entry = getSymbolTableEntryBase(this, DRI);
     getSymbolAddress(DRI, Value);
+    if (Value == UnknownAddressOrSize)
+      continue;
     if (Entry.n_sect == SectionIndex && Value > BeginOffset)
       if (!EndOffset || Value < EndOffset)
         EndOffset = Value;
@@ -578,7 +592,7 @@
     if ((MachOType & MachO::N_TYPE) == MachO::N_UNDF) {
       uint64_t Value;
       getSymbolAddress(DRI, Value);
-      if (Value)
+      if (Value && Value != UnknownAddressOrSize)
         Result |= SymbolRef::SF_Common;
     }
   }