[PATCH] D44672: [CodeGen] Disable UBSan for coroutine functions

[Brian Gesiak via Phabricator via cfe-commits]

modocache updated this revision to Diff 214370.
modocache added a comment.

Thanks for the review, @vsk! Sorry it took me so long to update this diff.

In the mailing list discussion, http://lists.llvm.org/pipermail/llvm-dev/2018-March/121925.html, you mentioned that I should use an allow-list of known good sanitizer options, rather than a deny-list of known bad ones (`-fsanitize=null`, in this case). However, at this time I'm only aware of problems with `-fsanitize=null`, so I don't know what else to exclude. In other words, an allow-list of known good sanitizers would, at this point, be every other sanitizer pass. So I figured for now, I'll just deny `-fsanitize=null`. Does that work for you?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D44672/new/

https://reviews.llvm.org/D44672

Files:
  clang/lib/CodeGen/CodeGenFunction.cpp
  clang/test/CodeGenCXX/ubsan-coroutines.cpp


Index: clang/test/CodeGenCXX/ubsan-coroutines.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/ubsan-coroutines.cpp
@@ -0,0 +1,49 @@
+// This test merely verifies that emitting the object file does not cause a
+// crash when the LLVM coroutines passes are run.
+// RUN: %clang_cc1 -emit-obj -std=c++2a -fsanitize=null %s -o %t.o
+
+namespace std::experimental {
+template <typename R, typename... T> struct coroutine_traits {
+  using promise_type = typename R::promise_type;
+};
+
+template <class Promise = void> struct coroutine_handle;
+template <> struct coroutine_handle<void> {
+  static coroutine_handle from_address(void *) noexcept;
+  coroutine_handle() = default;
+  template <class PromiseType>
+  coroutine_handle(coroutine_handle<PromiseType>) noexcept;
+};
+template <class Promise> struct coroutine_handle : coroutine_handle<void> {
+  coroutine_handle() = default;
+  static coroutine_handle from_address(void *) noexcept;
+};
+}
+
+struct suspend_always {
+  bool await_ready() noexcept;
+  void await_suspend(std::experimental::coroutine_handle<>) noexcept;
+  void await_resume() noexcept;
+};
+
+struct task {
+  struct promise_type {
+    task get_return_object() { return task(); }
+    suspend_always initial_suspend() { return {}; }
+    suspend_always final_suspend() { return {}; }
+    void return_void() {}
+    void unhandled_exception() {}
+  };
+};
+
+struct awaitable {
+  task await() { (void)co_await *this; }
+  bool await_ready() { return false; }
+  bool await_suspend(std::experimental::coroutine_handle<> awaiter) { return false; }
+  bool await_resume() { return false; }
+};
+
+int main() {
+  awaitable a;
+  a.await();
+}
Index: clang/lib/CodeGen/CodeGenFunction.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenFunction.cpp
+++ clang/lib/CodeGen/CodeGenFunction.cpp
@@ -732,6 +732,15 @@
       SanOpts.Mask &= ~SanitizerKind::CFIUnrelatedCast;
   }
 
+  // Ignore null checks in coroutine functions since the coroutines passes
+  // are not aware of how to move the extra UBSan instructions across the split
+  // coroutine boundaries.
+  if (D && SanOpts.has(SanitizerKind::Null))
+    if (const auto *FD = dyn_cast<FunctionDecl>(D))
+      if (FD->getBody() &&
+          FD->getBody()->getStmtClass() == Stmt::CoroutineBodyStmtClass)
+        SanOpts.Mask &= ~SanitizerKind::Null;
+
   // Apply xray attributes to the function (as a string, for now)
   if (D) {
     if (const auto *XRayAttr = D->getAttr<XRayInstrumentAttr>()) {


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