[PATCH] D145581: [clang-tidy] In C++17, callee is guaranteed to be sequenced before arguments.

[Martin Böhme via Phabricator via cfe-commits]

mboehme updated this revision to Diff 506507.
mboehme added a comment.

Changes in response to review comments.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D145581/new/

https://reviews.llvm.org/D145581

Files:
  clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
  clang-tools-extra/test/clang-tidy/checkers/bugprone/use-after-move.cpp


Index: clang-tools-extra/test/clang-tidy/checkers/bugprone/use-after-move.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/bugprone/use-after-move.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/bugprone/use-after-move.cpp
@@ -1,3 +1,4 @@
+// RUN: %check_clang_tidy -std=c++11 -check-suffixes=,CXX11 %s bugprone-use-after-move %t -- -- -fno-delayed-template-parsing
 // RUN: %check_clang_tidy -std=c++17-or-later %s bugprone-use-after-move %t -- -- -fno-delayed-template-parsing
 
 typedef decltype(nullptr) nullptr_t;
@@ -123,6 +124,7 @@
   A &operator=(A &&);
 
   void foo() const;
+  void bar(int i) const;
   int getInt() const;
 
   operator bool() const;
@@ -1307,6 +1309,30 @@
   }
 }
 
+// In a function call, the expression that determines the callee is sequenced
+// before the arguments -- but only in C++17 and later.
+namespace CalleeSequencedBeforeArguments {
+int consumeA(std::unique_ptr<A> a);
+
+void calleeSequencedBeforeArguments() {
+  {
+    std::unique_ptr<A> a;
+    a->bar(consumeA(std::move(a)));
+    // CHECK-NOTES-CXX11: [[@LINE-1]]:5: warning: 'a' used after it was moved
+    // CHECK-NOTES-CXX11: [[@LINE-2]]:21: note: move occurred here
+    // CHECK-NOTES-CXX11: [[@LINE-3]]:5: note: the use and move are unsequenced
+  }
+  {
+    std::unique_ptr<A> a;
+    std::unique_ptr<A> getArg(std::unique_ptr<A> a);
+    getArg(std::move(a))->bar(a->getInt());
+    // CHECK-NOTES: [[@LINE-1]]:31: warning: 'a' used after it was moved
+    // CHECK-NOTES: [[@LINE-2]]:12: note: move occurred here
+    // CHECK-NOTES-CXX11: [[@LINE-3]]:31: note: the use and move are unsequenced
+  }
+}
+} // namespace CalleeSequencedBeforeArguments
+
 // Some statements in templates (e.g. null, break and continue statements) may
 // be shared between the uninstantiated and instantiated versions of the
 // template and therefore have multiple parents. Make sure the sequencing code
Index: clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
===================================================================
--- clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
+++ clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
@@ -95,9 +95,29 @@
       return true;
   }
 
+  SmallVector<const Stmt *, 1> BeforeParents = getParentStmts(Before, Context);
+
+  // Since C++17, the callee of a call expression is guaranteed to be sequenced
+  // before all of the arguments.
+  // We handle this as a special case rather than using the general
+  // `getSequenceSuccessor` logic above because the callee expression doesn't
+  // have an unambiguous successor; the order in which arguments are evaluated
+  // is indeterminate.
+  if (Context->getLangOpts().CPlusPlus17) {
+    for (const Stmt *Parent : BeforeParents) {
+      if (const auto *call = dyn_cast<CallExpr>(Parent);
+          call && call->getCallee() == Before) {
+        for (const Expr *arg : call->arguments()) {
+          if (isDescendantOrEqual(After, arg, Context))
+            return true;
+        }
+      }
+    }
+  }
+
   // If 'After' is a parent of 'Before' or is sequenced after one of these
   // parents, we know that it is sequenced after 'Before'.
-  for (const Stmt *Parent : getParentStmts(Before, Context)) {
+  for (const Stmt *Parent : BeforeParents) {
     if (Parent == After || inSequence(Parent, After))
       return true;
   }


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