[clang-tidy] Fix crashing altera-struct-pack-align on invalid RecordDecls

[steakhal]

ping

[martong]

What happens if this checker runs on a forward declared class?

struct Foo;

I'd expect the pack/alignment info is missing also in that case.

clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.cpp

54

I'd mention first that packing and alignment info are meaningless for invalid declarations.

[steakhal]

• update comments
• move no-crash comment inline to the class member declaration

[steakhal]

In D114256#3149009, @martong wrote:

What happens if this checker runs on a forward declared class?

The matcher recordDecl(isStruct(), **isDefinition()**, unless(isExpansionInSystemHeader())) filters that case.

Thanks for the review @martong!

clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.cpp

54

Makes sense.

[martong]

LGTM!

[steakhal]

I plan to commit this stack on Monday.

clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.cpp

 void StructPackAlignCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *Struct = Result.Nodes.getNodeAs<RecordDecl>("struct");
 
   // Do not trigger on templated struct declarations because the packing and
   // alignment requirements are unknown.
   if (Struct->isTemplated())
      return;
 
+  // Packing and alignment requirements for invalid decls are meaningless.
+  if (Struct->isInvalidDecl())
+    return;
+
   // Get sizing info for the struct.
   llvm::SmallVector<std::pair<unsigned int, unsigned int>, 10> FieldSizes;
   unsigned int TotalBitSize = 0;
   for (const FieldDecl *StructField : Struct->fields()) {
     // For each StructField, record how big it is (in bits).
     // Would be good to use a pair of <offset, size> to advise a better
     // packing order.
     QualType StructFieldTy = StructField->getType();

clang-tools-extra/test/clang-tidy/checkers/altera-struct-pack-align-invalid-decl-no-crash.cpp

+// RUN: %check_clang_tidy -expect-clang-tidy-error %s altera-struct-pack-align %t -- -header-filter=.*
+
+struct Foo {
+  member; // no-crash
+};
+// CHECK-MESSAGES: :[[@LINE-2]]:3: error: C++ requires a type specifier for all declarations [clang-diagnostic-error]