[yaml2obj][MachO] - Fix PubName/PubType handling.

`PubName` and `PubType` are optional fields since D80722.

They are defined as:
  Optional<PubSection> PubNames;
  Optional<PubSection> PubTypes;

And initialized in the following way:
  IO.mapOptional("debug_pubnames", DWARF.PubNames);
  IO.mapOptional("debug_pubtypes", DWARF.PubTypes);

But problem is that because of the issue in `YAMLTraits.cpp`,
when there are no `debug_pubnames`/`debug_pubtypes` keys in a YAML description,
they are not initialized to `Optional::None` as the code expects, but they
are initialized to default `PubSection()` instances.

Because of this, the `if` condition in the following code is always true:

if (Obj.DWARF.PubNames)
  Err = DWARFYAML::emitPubSection(OS, *Obj.DWARF.PubNames,
                                  Obj.IsLittleEndian);

What means `emitPubSection` is always called and it writes few values.

This patch fixes the issue. I've reduced `sizeofcmds` by size of data
previously written because of this bug.

Differential revision: https://reviews.llvm.org/D81686

diff --git a/llvm/lib/Support/YAMLTraits.cpp b/llvm/lib/Support/YAMLTraits.cpp
index f27be3e..752fab2 100644 (file)
--- a/llvm/lib/Support/YAMLTraits.cpp
+++ b/llvm/lib/Support/YAMLTraits.cpp
@@ -166,6 +166,8 @@ bool Input::preflightKey(const char *Key, bool Required, bool, bool &UseDefault,
   if (!MN) {
     if (Required || !isa<EmptyHNode>(CurrentNode))
       setError(CurrentNode, "not a mapping");
+    else
+      UseDefault = true;
     return false;
   }
   MN->ValidKeys.push_back(Key);

diff --git a/llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml b/llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml
index 4faac06..0bc510d 100644 (file)
--- a/llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml
+++ b/llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml
@@ -356,7 +356,8 @@ DWARF:
 ## contents, if the "debug_pubnames"/"debug_pubtypes" entry doesn't exist in the
 ## "DWARF" entry.
 
-# RUN: yaml2obj --docnum=2 %s | obj2yaml | FileCheck %s --check-prefix=EMPTY
+# RUN: yaml2obj --docnum=2 %s -o %t2
+# RUN: obj2yaml %t2 | FileCheck %s --check-prefix=EMPTY
 
 #      EMPTY: Sections:
 # EMPTY-NEXT:   - sectname:        __debug_pubnames
@@ -394,7 +395,7 @@ FileHeader:
   cpusubtype: 0x00000003
   filetype:   0x0000000A
   ncmds:      1
-  sizeofcmds: 1800
+  sizeofcmds: 1772
   flags:      0x00000000
   reserved:   0x00000000
 LoadCommands: