[clang] Add Clang attribute to ensure that fields are initialized explicitly (PR #102040)

[Erich Keane via cfe-commits]

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@@ -6014,6 +6014,10 @@ static void handleNoMergeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   D->addAttr(NoMergeAttr::Create(S.Context, AL));
 }
 
+static void handleExplicitInitAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  D->addAttr(ExplicitInitAttr::Create(S.Context, AL));
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erichkeane wrote:

I think we need more explicit checking here.  This needs to limit to an aggregate type in some way, I'd very much not want us to ignore this silently on non-aggregates.  Though perhaps the diagnostic needs to happen later?  Perhaps handling this needs to look at the `RecordDecl` and make the determination off of that?

https://github.com/llvm/llvm-project/pull/102040