Common symbols don't have a value.

At least not in the interface exposed by ObjectFile. This matches what ELF and
COFF implement.

Adjust existing code that was expecting them to have values. No overall
functionality change intended.

Another option would be to change the interface and the ELF and COFF
implementations to say that the value of a common symbol is its size.

llvm-svn: 241593
diff --git a/llvm/tools/dsymutil/MachODebugMapParser.cpp b/llvm/tools/dsymutil/MachODebugMapParser.cpp
index bec9591..76fc761 100644
--- a/llvm/tools/dsymutil/MachODebugMapParser.cpp
+++ b/llvm/tools/dsymutil/MachODebugMapParser.cpp
@@ -197,10 +197,14 @@
   CurrentObjectAddresses.clear();
 
   for (auto Sym : CurrentObjectHolder.Get().symbols()) {
-
-    uint64_t Addr = Sym.getValue();
-    if (Addr == UnknownAddress)
-      continue;
+    uint64_t Addr;
+    if (Sym.getFlags() & SymbolRef::SF_Common) {
+      Addr = Sym.getCommonSize();
+    } else {
+      Addr = Sym.getValue();
+      if (Addr == UnknownAddress)
+        continue;
+    }
     ErrorOr<StringRef> Name = Sym.getName();
     if (!Name)
       continue;