[clang-tidy] Handle incomplete types in bugprone-undefined-memory-manipulation check.

[rnkovacs]

Summary

bugprone-undefined-memory-manipulation check crashes on incomplete types. This diff fixes that by assuming they are TriviallyCopyable by default.

[alexfh]

LG. Thank you for the fix!

clang-tidy/bugprone/UndefinedMemoryManipulationCheck.cpp

 
 namespace {
 AST_MATCHER(CXXRecordDecl, isNotTriviallyCopyable) {
-  return !Node.isTriviallyCopyable();
+  // For incomplete types, assume they are TriviallyCopyable.
+  return Node.hasDefinition() ? !Node.isTriviallyCopyable() : false;
 }
 } // namespace
 

test/clang-tidy/bugprone-undefined-memory-manipulation.cpp

   int vb;
 };
 
+// Incomplete type, assume it is TriviallyCopyable.
+struct NoDef;
+
+void f(NoDef *s) {
+  memset(s, 0, 5);
+}
+
 template <typename T>
 void memset_temp(T *b) {
   memset(b, 0, sizeof(T));