[clang-tools-extra] [clang-tidy] Add check to diagnose coroutine-hostile RAII objects (PR #68738)

[Sam McCall via cfe-commits]

================
@@ -0,0 +1,98 @@
+//===--- CoroutineHostileRAII.cpp - clang-tidy ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "CoroutineHostileRAIICheck.h"
+#include "../utils/OptionsUtils.h"
+#include "clang/AST/Attr.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/AST/Stmt.h"
+#include "clang/AST/Type.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersInternal.h"
+#include "clang/Basic/AttrKinds.h"
+#include "clang/Basic/DiagnosticIDs.h"
+
+using namespace clang::ast_matchers;
+namespace clang::tidy::misc {
+namespace {
+using clang::ast_matchers::internal::BoundNodesTreeBuilder;
+
+AST_MATCHER_P(Stmt, forEachPrevStmt, ast_matchers::internal::Matcher<Stmt>,
+              InnerMatcher) {
+  DynTypedNode P;
+  bool IsHostile = false;
+  for (const Stmt *Child = &Node; Child; Child = P.get<Stmt>()) {
+    auto Parents = Finder->getASTContext().getParents(*Child);
+    if (Parents.empty())
+      break;
+    P = *Parents.begin();
+    auto *PCS = P.get<CompoundStmt>();
+    if (!PCS)
+      continue;
+    for (const auto &Sibling : PCS->children()) {
+      // Child contains suspension. Siblings after Child do not persist across
+      // this suspension.
+      if (Sibling == Child)
+        break;
+      // In case of a match, add the bindings as a separate match. Also don't
+      // clear the bindings if a match is not found (unlike Matcher::matches).
+      BoundNodesTreeBuilder SiblingBuilder;
+      if (InnerMatcher.matches(*Sibling, Finder, &SiblingBuilder)) {
+        Builder->addMatch(SiblingBuilder);
+        IsHostile = true;
+      }
+    }
+  }
+  return IsHostile;
+}
+} // namespace
+
+CoroutineHostileRAIICheck::CoroutineHostileRAIICheck(StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      RAIITypesList(utils::options::parseStringList(
+          Options.get("RAIITypesList", "std::lock_guard;std::scoped_lock"))) {}
+
+void CoroutineHostileRAIICheck::registerMatchers(MatchFinder *Finder) {
+  // A suspension happens with co_await or co_yield.
+  auto ScopedLockable = varDecl(hasType(hasCanonicalType(hasDeclaration(
+                                    hasAttr(attr::Kind::ScopedLockable)))))
+                            .bind("scoped-lockable");
+  auto OtherRAII = varDecl(hasType(hasCanonicalType(hasDeclaration(
+                               namedDecl(hasAnyName(RAIITypesList))))))
+                       .bind("raii");
+  Finder->addMatcher(expr(anyOf(coawaitExpr(), coyieldExpr()),
+                          forEachPrevStmt(declStmt(forEach(
----------------
sam-mccall wrote:

this implies a quadratic algorithm: every suspend point is going to walk every prior statement. (the matcher framework has memoization but it won't apply here).

It may well be fine in practice, and I don't really have a better suggestion - leaning heavily on matchers is idiomatic in clang-tidy, and is rarely efficient :-) No action needed here.

https://github.com/llvm/llvm-project/pull/68738