[clang] Respect the [[clang::unsafe_buffer_usage]] attribute for field and constructor initializers (PR #91991)

[Dana Jansens via cfe-commits]

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@@ -3912,3 +3896,56 @@ void clang::checkUnsafeBufferUsage(const Decl *D,
     }
   }
 }
+
+void clang::checkUnsafeBufferUsage(const Decl *D,
+                                   UnsafeBufferUsageHandler &Handler,
+                                   bool EmitSuggestions) {
+#ifndef NDEBUG
+  Handler.clearDebugNotes();
+#endif
+
+  assert(D);
+
+  SmallVector<Stmt *> Stmts;
+
+  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
+    // We do not want to visit a Lambda expression defined inside a method
+    // independently. Instead, it should be visited along with the outer method.
+    // FIXME: do we want to do the same thing for `BlockDecl`s?
+    if (const auto *MD = dyn_cast<CXXMethodDecl>(D)) {
+      if (MD->getParent()->isLambda() && MD->getParent()->isLocalClass())
+        return;
+    }
+
+    for (FunctionDecl *FReDecl : FD->redecls()) {
+      if (FReDecl->isExternC()) {
+        // Do not emit fixit suggestions for functions declared in an
+        // extern "C" block.
+        EmitSuggestions = false;
+        break;
+      }
+    }
+
+    Stmts.push_back(FD->getBody());
+
+    if (const auto *ID = dyn_cast<CXXConstructorDecl>(D)) {
----------------
danakj wrote:

I don't think we have that option, because they are not statements: https://github.com/llvm/llvm-project/blob/5545f76dc94e76ef6800823bdd1e107ad2264717/clang/include/clang/Basic/StmtNodes.td#L133-L134

That's why this code has to pull the `getInit()` out of it to find a statement.

https://github.com/llvm/llvm-project/pull/91991