1 files changed, 56 insertions, 0 deletions
diff --git a/build/clang-plugin/NonTrivialTypeInFfiChecker.cpp b/build/clang-plugin/NonTrivialTypeInFfiChecker.cpp
new file mode 100644
index 0000000000..f482fb131f
--- /dev/null
+++ b/build/clang-plugin/NonTrivialTypeInFfiChecker.cpp
@@ -0,0 +1,56 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "NonTrivialTypeInFfiChecker.h"
+#include "CustomMatchers.h"
+
+void NonTrivialTypeInFfiChecker::registerMatchers(MatchFinder *AstMatcher) {
+  AstMatcher->addMatcher(functionDecl(isExternC()).bind("func"), this);
+}
+
+void NonTrivialTypeInFfiChecker::check(const MatchFinder::MatchResult &Result) {
+  static DenseSet<const FunctionDecl *> CheckedFunctionDecls;
+
+  const FunctionDecl *func = Result.Nodes.getNodeAs<FunctionDecl>("func");
+  // Don't report errors on the same declarations more than once.
+  if (!CheckedFunctionDecls.insert(func).second) {
+    return;
+  }
+
+  if (inThirdPartyPath(func)) {
+    return;
+  }
+
+  auto NoteFor = [](const QualType &T) -> std::string {
+    std::string s = "Please consider using a pointer or reference";
+    if (T->getAs<TemplateSpecializationType>()) {
+      s += ", or explicitly instantiating the template";
+    }
+    return s + " instead";
+  };
+
+  for (ParmVarDecl *p : func->parameters()) {
+    QualType T = p->getType().getUnqualifiedType();
+    if (!T->isVoidType() && !T->isReferenceType() &&
+        !T.isTriviallyCopyableType(*Result.Context)) {
+      diag(p->getLocation(),
+           "Type %0 must not be used as parameter to extern "
+           "\"C\" function",
+           DiagnosticIDs::Error)
+          << T;
+      diag(p->getLocation(), NoteFor(T), DiagnosticIDs::Note);
+    }
+  }
+
+  QualType T = func->getReturnType().getUnqualifiedType();
+  if (!T->isVoidType() && !T->isReferenceType() &&
+      !T.isTriviallyCopyableType(*Result.Context)) {
+    diag(func->getLocation(),
+         "Type %0 must not be used as return type of "
+         "extern \"C\" function",
+         DiagnosticIDs::Error)
+        << T;
+    diag(func->getLocation(), NoteFor(T), DiagnosticIDs::Note);
+  }
+}