[lldb][COFF] Map symbols without base+complex type as 'Data' type

Both LLD and GNU ld write global/static variables to the COFF symbol
table with `IMAGE_SYM_TYPE_NULL` and `IMAGE_SYM_DTYPE_NULL` type. Map
these symbols as 'Data' type in the symtab to allow these symbols to be
used in expressions and printable.

Reviewed By: labath, DavidSpickett

Differential Revision: https://reviews.llvm.org/D134585

Author: alvinhochun

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

@@ -379,6 +379,13 @@ lldb::SymbolType ObjectFilePECOFF::MapSymbolType(uint16_t coff_symbol_type) {
   if (complex_type == llvm::COFF::IMAGE_SYM_DTYPE_FUNCTION) {
     return lldb::eSymbolTypeCode;
   }
+  const auto base_type = coff_symbol_type & 0xff;
+  if (base_type == llvm::COFF::IMAGE_SYM_TYPE_NULL &&
+      complex_type == llvm::COFF::IMAGE_SYM_DTYPE_NULL) {
+    // Unknown type. LLD and GNU ld uses this for variables on MinGW, so
+    // consider these symbols to be data to enable printing.
+    return lldb::eSymbolTypeData;
+  }
   return lldb::eSymbolTypeInvalid;
 }
 

lldb/test/Shell/ObjectFile/PECOFF/symbol.yaml

@@ -6,7 +6,7 @@
 
 # CHECK: Type     File Address/Value {{.*}} Size            Flags           Name
 # CHECK: Code     0x0000000040001000        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} entry
-# CHECK:          0x0000000040002000        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} variable
+# CHECK: Data     0x0000000040002000        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} variable
 # CHECK: Absolute 0x00000000deadbeef        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} absolute_symbol
 
 --- !COFF

lldb/test/Shell/ObjectFile/PECOFF/symbols-export-table.yaml

@@ -15,7 +15,7 @@
 # CHECK-NEXT: 4294967295     Code       0x0000000180001020        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} aliasFunc
 # CHECK-NEXT: 4294967295   X Additional 0x0000000180003000        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} exportInt
 # CHECK-NEXT: 4294967295     Data       0x0000000180003004        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} aliasInt
-# CHECK-NEXT: 4294967295     Invalid    0x0000000180003008        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} internalInt
+# CHECK-NEXT: 4294967295     Data       0x0000000180003008        0x{{[0-9a-f]+}} 0x{{[0-9a-f]+}} internalInt
 # CHECK-EMPTY:
 
 # Test file generated with: