[PATCH] D81686: [yaml2obj][MachO] - Fix PubName/PubType handling.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: jhenderson, MaskRay, Higuoxing, aprantl.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

`PubName` and `PubType` are optional fields since D80722 <https://reviews.llvm.org/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.

I need this fix (in YAMLTraits.cpp) for D81655 <https://reviews.llvm.org/D81655>.


https://reviews.llvm.org/D81686

Files:
  llvm/lib/Support/YAMLTraits.cpp
  llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml


Index: llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml
===================================================================
--- llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml
+++ llvm/test/ObjectYAML/MachO/DWARF-pubsections.yaml
@@ -356,7 +356,8 @@
 ## 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 @@
   cpusubtype: 0x00000003
   filetype:   0x0000000A
   ncmds:      1
-  sizeofcmds: 1800
+  sizeofcmds: 1772
   flags:      0x00000000
   reserved:   0x00000000
 LoadCommands:
Index: llvm/lib/Support/YAMLTraits.cpp
===================================================================
--- llvm/lib/Support/YAMLTraits.cpp
+++ llvm/lib/Support/YAMLTraits.cpp
@@ -166,6 +166,8 @@
   if (!MN) {
     if (Required || !isa<EmptyHNode>(CurrentNode))
       setError(CurrentNode, "not a mapping");
+    else
+      UseDefault = true;
     return false;
   }
   MN->ValidKeys.push_back(Key);


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