[YAML] Don't validate Fill::Size after error

[vitalybuka]

Size is required, so we don't know if it's in
uninitialized state after the previous error.

Triggers msan on llvm/test/tools/yaml2obj/ELF/custom-fill.yaml NOSIZE test.

We have Fill Section with Pattern, but no size. Before the fix it produced error:

YAML:169:5: error: missing required key 'Size'
  - Type:    Fill
    ^
YAML:169:5: error: "Size" can't be 0 when "Pattern" is not empty
  - Type:    Fill

The same applies to MachOYAML::Section fields content and size.
However MachOYAML::Section matches size first, so on error,
content is not set anyway. Added error checking just in case.

[llvmbot]

@llvm/pr-subscribers-llvm-support

@llvm/pr-subscribers-objectyaml

Author: Vitaly Buka (vitalybuka)

Changes

Size is required, so we don't know if it's in
uninitialized state after the previous error.

Triggers msan on llvm/test/tools/yaml2obj/ELF/custom-fill.yaml

---

Full diff: https://github.com/llvm/llvm-project/pull/123280.diff

1 Files Affected:

• (modified) llvm/lib/ObjectYAML/ELFYAML.cpp (+3-1)

diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index e0e941cff94c52..1d52cdef79400f 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -1750,7 +1750,9 @@ void MappingTraits<std::unique_ptr<ELFYAML::Chunk>>::mapping(
 std::string MappingTraits<std::unique_ptr<ELFYAML::Chunk>>::validate(
     IO &io, std::unique_ptr<ELFYAML::Chunk> &C) {
   if (const auto *F = dyn_cast<ELFYAML::Fill>(C.get())) {
-    if (F->Pattern && F->Pattern->binary_size() != 0 && !F->Size)
+    // Can't check the `Size`, as it's required and may be left uninitialized by
+    // previous error.
+    if (!io.error() && F->Pattern && F->Pattern->binary_size() != 0 && !F->Size)
       return "\"Size\" can't be 0 when \"Pattern\" is not empty";
     return "";
   }

[jh7370]

LGTM, but might want to get @MaskRay to give a thumbs up to, given he's made a comment.