[clang] [clang][CFG] Sequence RHS before LHS for overloaded assignment operators in CFG to match C++17 rules (PR #181113)
Alex Wang via cfe-commits
cfe-commits at lists.llvm.org
Thu Feb 12 10:14:40 PST 2026
https://github.com/aeft updated https://github.com/llvm/llvm-project/pull/181113
>From 443bcc74263343aa2105d14b851f128356171621 Mon Sep 17 00:00:00 2001
From: Alex Wang <yesterda9 at gmail.com>
Date: Thu, 12 Feb 2026 02:13:05 -0800
Subject: [PATCH 1/3] [clang][CFG] Sequence RHS before LHS for overloaded
assignment operators in CFG to match C++17 rules
---
clang/lib/Analysis/CFG.cpp | 18 ++++++++--
.../Analysis/cfg-assignment-eval-order.cpp | 29 ++++++++++++++++
.../test/Analysis/missing-bind-temporary.cpp | 34 +++++++++----------
3 files changed, 62 insertions(+), 19 deletions(-)
create mode 100644 clang/test/Analysis/cfg-assignment-eval-order.cpp
diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index 8001a67a5e158..1d2085ca62791 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -656,6 +656,7 @@ class CFGBuilder {
bool ExternallyDestructed = false);
CFGBlock *VisitStmt(Stmt *S, AddStmtChoice asc);
CFGBlock *VisitChildren(Stmt *S);
+ CFGBlock *VisitCallExprChildren(CallExpr *C);
CFGBlock *VisitNoRecurse(Expr *E, AddStmtChoice asc);
CFGBlock *VisitOMPExecutableDirective(OMPExecutableDirective *D,
AddStmtChoice asc);
@@ -2542,6 +2543,19 @@ CFGBlock *CFGBuilder::VisitChildren(Stmt *S) {
return B;
}
+CFGBlock *CFGBuilder::VisitCallExprChildren(CallExpr *C) {
+ // C++17 onwards require that the right operand is sequenced before the left
+ // operand.
+ if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(C)) {
+ if (OCE->isAssignmentOp()) {
+ Visit(OCE->getArg(0));
+ Visit(OCE->getArg(1));
+ return Visit(OCE->getCallee());
+ }
+ }
+ return VisitChildren(C);
+}
+
CFGBlock *CFGBuilder::VisitInitListExpr(InitListExpr *ILE, AddStmtChoice asc) {
if (asc.alwaysAdd(*this, ILE)) {
autoCreateBlock();
@@ -2879,7 +2893,7 @@ CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, AddStmtChoice asc) {
autoCreateBlock();
appendCall(Block, C);
- return VisitChildren(C);
+ return VisitCallExprChildren(C);
}
if (Block) {
@@ -2903,7 +2917,7 @@ CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, AddStmtChoice asc) {
addSuccessor(Block, &cfg->getExit());
}
- return VisitChildren(C);
+ return VisitCallExprChildren(C);
}
CFGBlock *CFGBuilder::VisitChooseExpr(ChooseExpr *C,
diff --git a/clang/test/Analysis/cfg-assignment-eval-order.cpp b/clang/test/Analysis/cfg-assignment-eval-order.cpp
new file mode 100644
index 0000000000000..a792b7f7b33dd
--- /dev/null
+++ b/clang/test/Analysis/cfg-assignment-eval-order.cpp
@@ -0,0 +1,29 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=debug.DumpCFG -std=c++17 %s > %t 2>&1
+// RUN: FileCheck --input-file=%t %s
+
+// CHECK-LABEL: void test(Map &m, int a, int b)
+// CHECK: 1: operator=
+// CHECK-NEXT: 2: [B1.1] (ImplicitCastExpr, FunctionToPointerDecay, Map &(*)(const Map &))
+// CHECK-NEXT: 3: operator[]
+// CHECK-NEXT: 4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, Map &(*)(int))
+// CHECK-NEXT: 5: m
+// CHECK-NEXT: 6: a
+// CHECK-NEXT: 7: [B1.6] (ImplicitCastExpr, LValueToRValue, int)
+// CHECK-NEXT: 8: [B1.5][[B1.7]] (OperatorCall)
+// CHECK-NEXT: 9: [B1.8] (ImplicitCastExpr, NoOp, const Map)
+// CHECK-NEXT: 10: operator[]
+// CHECK-NEXT: 11: [B1.10] (ImplicitCastExpr, FunctionToPointerDecay, Map &(*)(int))
+// CHECK-NEXT: 12: m
+// CHECK-NEXT: 13: b
+// CHECK-NEXT: 14: [B1.13] (ImplicitCastExpr, LValueToRValue, int)
+// CHECK-NEXT: 15: [B1.12][[B1.14]] (OperatorCall)
+// CHECK-NEXT: 16: [B1.15] = [B1.9] (OperatorCall)
+
+struct Map {
+ Map &operator[](int);
+ Map &operator=(const Map &);
+};
+
+void test(Map &m, int a, int b) {
+ m[b] = m[a];
+}
\ No newline at end of file
diff --git a/clang/test/Analysis/missing-bind-temporary.cpp b/clang/test/Analysis/missing-bind-temporary.cpp
index 3d1af469dc01c..2ce733b0986b0 100644
--- a/clang/test/Analysis/missing-bind-temporary.cpp
+++ b/clang/test/Analysis/missing-bind-temporary.cpp
@@ -23,11 +23,11 @@ class B {
// CHECK-NEXT: 2: B i;
// CHECK-NEXT: 3: operator=
// CHECK-NEXT: 4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, B &(*)(B &&) noexcept)
-// CHECK-NEXT: 5: i
-// CHECK-NEXT: 6: {} (CXXConstructExpr, [B1.7], [B1.8], B)
-// CHECK-NEXT: 7: [B1.6] (BindTemporary)
-// CHECK-NEXT: 8: [B1.7]
-// CHECK-NEXT: 9: [B1.5] = [B1.8] (OperatorCall)
+// CHECK-NEXT: 5: {} (CXXConstructExpr, [B1.6], [B1.7], B)
+// CHECK-NEXT: 6: [B1.5] (BindTemporary)
+// CHECK-NEXT: 7: [B1.6]
+// CHECK-NEXT: 8: i
+// CHECK-NEXT: 9: [B1.8] = [B1.7] (OperatorCall)
// CHECK-NEXT: 10: ~B() (Temporary object destructor)
// CHECK-NEXT: 11: [B1.2].~B() (Implicit destructor)
void foo(int) {
@@ -60,13 +60,13 @@ class B {
// CHECK-NEXT: 2: B i;
// CHECK-NEXT: 3: operator=
// CHECK-NEXT: 4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, B &(*)(B &&) noexcept)
-// CHECK-NEXT: 5: i
-// CHECK-NEXT: 6: {} (CXXConstructExpr, [B1.7], [B1.8], B)
-// CHECK-NEXT: 7: [B1.6] (BindTemporary)
-// CHECK-NEXT: 8: [B1.7]
-// CHECK-NEXT: 9: [B1.5] = [B1.8] (OperatorCall)
-// CHECK-NEXT: 10: ~B() (Temporary object destructor)
-// CHECK-NEXT: 11: [B1.2].~B() (Implicit destructor)
+// CHECK-NEXT: 5: {} (CXXConstructExpr, [B1.6], [B1.7], B)
+// CHECK-NEXT: 6: [B1.5] (BindTemporary)
+// CHECK-NEXT: 7: [B1.6]
+// CHECK-NEXT: 8: i
+// CHECK-NEXT: 9: [B1.8] = [B1.7] (OperatorCall)
+// CHECK-NEXT: 10: ~B() (Temporary object destructor)
+// CHECK-NEXT: 11: [B1.2].~B() (Implicit destructor)
template <typename T> void foo(T) {
B i;
i = {};
@@ -101,12 +101,12 @@ class B {
// CHECK-NEXT: 2: B i;
// CHECK-NEXT: 3: operator=
// CHECK-NEXT: 4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, B &(*)(B &&) noexcept)
-// CHECK-NEXT: 5: i
+// CHECK-NEXT: 5: {}
// CHECK-NEXT: 6: {}
-// CHECK-NEXT: 7: {}
-// CHECK-NEXT: 8: [B1.7] (BindTemporary)
-// CHECK-NEXT: 9: [B1.8]
-// CHECK-NEXT: 10: [B1.5] = [B1.9] (OperatorCall)
+// CHECK-NEXT: 7: [B1.6] (BindTemporary)
+// CHECK-NEXT: 8: [B1.7]
+// CHECK-NEXT: 9: i
+// CHECK-NEXT: 10: [B1.9] = [B1.8] (OperatorCall)
// CHECK-NEXT: 11: ~B() (Temporary object destructor)
// CHECK-NEXT: 12: [B1.2].~B() (Implicit destructor)
template <typename T> void foo(T) {
>From 3cfe7c092591636571d8658170234f33ce5dd1e6 Mon Sep 17 00:00:00 2001
From: Alex Wang <yesterda9 at gmail.com>
Date: Thu, 12 Feb 2026 02:44:12 -0800
Subject: [PATCH 2/3] fixup! [clang][CFG] Sequence RHS before LHS for
overloaded assignment operators in CFG to match C++17 rules
---
clang/test/Analysis/cfg-assignment-eval-order.cpp | 4 ++--
clang/test/Analysis/scopes-cfg-output.cpp | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/clang/test/Analysis/cfg-assignment-eval-order.cpp b/clang/test/Analysis/cfg-assignment-eval-order.cpp
index a792b7f7b33dd..5315eb3fcda3a 100644
--- a/clang/test/Analysis/cfg-assignment-eval-order.cpp
+++ b/clang/test/Analysis/cfg-assignment-eval-order.cpp
@@ -9,14 +9,14 @@
// CHECK-NEXT: 5: m
// CHECK-NEXT: 6: a
// CHECK-NEXT: 7: [B1.6] (ImplicitCastExpr, LValueToRValue, int)
-// CHECK-NEXT: 8: [B1.5][[B1.7]] (OperatorCall)
+// CHECK-NEXT: 8: [B1.5]{{\[\[}}B1.7]] (OperatorCall)
// CHECK-NEXT: 9: [B1.8] (ImplicitCastExpr, NoOp, const Map)
// CHECK-NEXT: 10: operator[]
// CHECK-NEXT: 11: [B1.10] (ImplicitCastExpr, FunctionToPointerDecay, Map &(*)(int))
// CHECK-NEXT: 12: m
// CHECK-NEXT: 13: b
// CHECK-NEXT: 14: [B1.13] (ImplicitCastExpr, LValueToRValue, int)
-// CHECK-NEXT: 15: [B1.12][[B1.14]] (OperatorCall)
+// CHECK-NEXT: 15: [B1.12]{{\[\[}}B1.14]] (OperatorCall)
// CHECK-NEXT: 16: [B1.15] = [B1.9] (OperatorCall)
struct Map {
diff --git a/clang/test/Analysis/scopes-cfg-output.cpp b/clang/test/Analysis/scopes-cfg-output.cpp
index 6ed6f3638f75b..ac8ff1179a994 100644
--- a/clang/test/Analysis/scopes-cfg-output.cpp
+++ b/clang/test/Analysis/scopes-cfg-output.cpp
@@ -907,10 +907,10 @@ void test_for_compound_and_break() {
// CHECK-NEXT: 5: auto &i
// CHECK-NEXT: 6: operator=
// CHECK-NEXT: 7: [B4.6] (ImplicitCastExpr, FunctionToPointerDecay, A &(*)(const A &)
-// CHECK-NEXT: 8: i
-// CHECK-NEXT: 9: b
-// CHECK-NEXT: 10: [B4.9] (ImplicitCastExpr, NoOp, const A)
-// CHECK-NEXT: 11: [B4.8] = [B4.10] (OperatorCall)
+// CHECK-NEXT: 8: b
+// CHECK-NEXT: 9: [B4.8] (ImplicitCastExpr, NoOp, const A)
+// CHECK-NEXT: 10: i
+// CHECK-NEXT: 11: [B4.10] = [B4.9] (OperatorCall)
// CHECK-NEXT: 12: CFGScopeEnd(i)
// CHECK-NEXT: Preds (1): B2
// CHECK-NEXT: Succs (1): B3
>From 946f29dcd2d41353d506e74aa28ef0cee4c7f8c3 Mon Sep 17 00:00:00 2001
From: Alex Wang <yesterda9 at gmail.com>
Date: Thu, 12 Feb 2026 10:14:26 -0800
Subject: [PATCH 3/3] fixup! [clang][CFG] Sequence RHS before LHS for
overloaded assignment operators in CFG to match C++17 rules
---
clang/lib/Analysis/CFG.cpp | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index 1d2085ca62791..3827b0c341664 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -2544,14 +2544,14 @@ CFGBlock *CFGBuilder::VisitChildren(Stmt *S) {
}
CFGBlock *CFGBuilder::VisitCallExprChildren(CallExpr *C) {
- // C++17 onwards require that the right operand is sequenced before the left
- // operand.
- if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(C)) {
- if (OCE->isAssignmentOp()) {
- Visit(OCE->getArg(0));
- Visit(OCE->getArg(1));
- return Visit(OCE->getCallee());
- }
+ // For overloaded assignment operators, visit arguments in reverse order (LHS
+ // then RHS) so that RHS is sequenced before LHS in the CFG, matching C++17
+ // sequencing rules.
+ if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(C);
+ OCE && OCE->isAssignmentOp()) {
+ Visit(OCE->getArg(0));
+ Visit(OCE->getArg(1));
+ return Visit(OCE->getCallee());
}
return VisitChildren(C);
}
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