[PATCH] D155547: CPP-4580 Model lifetime of a variable declared in for condition in CFG correctly

Tomasz Kamiński via Phabricator via cfe-commits Mon, 17 Jul 2023 23:21:23 -0700

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Per [stmt.for] p1 (https://eel.is/c++draft/stmt.for#1) the following
'for' and `while` statement are equivalent

  for (; A c = b; b.c) {
    A d;
  }
  
  while (A c = b) {
    A d;
    b.c;
  }

As a consequence, the variable declared in for condition expression
should be destroyed after the increment expression.

Co-authored-by: Tomasz Kamiński <tomasz.kamińs...@sonarsource.com>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D155547

Files:
  clang/lib/Analysis/CFG.cpp
  clang/test/Analysis/auto-obj-dtors-cfg-output.cpp
  clang/test/Analysis/lifetime-cfg-output.cpp
  clang/test/Analysis/scopes-cfg-output.cpp

Index: clang/test/Analysis/scopes-cfg-output.cpp
===================================================================
--- clang/test/Analysis/scopes-cfg-output.cpp
+++ clang/test/Analysis/scopes-cfg-output.cpp
@@ -25,6 +25,7 @@
 // CHECK:      [B0 (EXIT)]
 // CHECK-NEXT:   Preds (1): B1
   operator int() const { return 1; }
+  int *p;
 };
 
 int getX();
@@ -524,6 +525,10 @@
 // CHECK-NEXT:   Preds (1): B4
 // CHECK-NEXT:   Succs (1): B0
 // CHECK:      [B2]
+// CHECK-NEXT:   1: b
+// CHECK-NEXT:   2: [B2.1].p
+// CHECK-NEXT:   3: [B4.5].~A() (Implicit destructor)
+// CHECK-NEXT:   4: CFGScopeEnd(b)
 // CHECK-NEXT:   Preds (1): B3
 // CHECK-NEXT:   Succs (1): B4
 // CHECK:      [B3]
@@ -532,8 +537,6 @@
 // CHECK-NEXT:   3: A c;
 // CHECK-NEXT:   4: [B3.3].~A() (Implicit destructor)
 // CHECK-NEXT:   5: CFGScopeEnd(c)
-// CHECK-NEXT:   6: [B4.5].~A() (Implicit destructor)
-// CHECK-NEXT:   7: CFGScopeEnd(b)
 // CHECK-NEXT:   Preds (1): B4
 // CHECK-NEXT:   Succs (1): B2
 // CHECK:      [B4]
@@ -548,7 +551,7 @@
 // CHECK-NEXT:   9: [B4.7]
 // CHECK-NEXT:  10: [B4.9] (ImplicitCastExpr, UserDefinedConversion, int)
 // CHECK-NEXT:  11: [B4.10] (ImplicitCastExpr, IntegralToBoolean, _Bool)
-// CHECK-NEXT:   T: for (...; [B4.11]; )
+// CHECK-NEXT:   T: for (...; [B4.11]; ...)
 // CHECK-NEXT:   Preds (2): B2 B5
 // CHECK-NEXT:   Succs (2): B3 B1
 // CHECK:      [B5]
@@ -560,7 +563,7 @@
 // CHECK:      [B0 (EXIT)]
 // CHECK-NEXT:   Preds (1): B1
 void test_for_implicit_scope() {
-  for (A a; A b = a; )
+  for (A a; A b = a; b.p)
     A c;
 }
 
@@ -579,6 +582,10 @@
 // CHECK-NEXT:   Preds (2): B8 B10
 // CHECK-NEXT:   Succs (1): B0
 // CHECK:      [B2]
+// CHECK-NEXT:   1: c
+// CHECK-NEXT:   2: [B2.1].p
+// CHECK-NEXT:   3: [B10.5].~A() (Implicit destructor)
+// CHECK-NEXT:   4: CFGScopeEnd(c)
 // CHECK-NEXT:   Preds (2): B3 B6
 // CHECK-NEXT:   Succs (1): B10
 // CHECK:      [B3]
@@ -587,8 +594,6 @@
 // CHECK-NEXT:   3: [B3.2].~A() (Implicit destructor)
 // CHECK-NEXT:   4: [B9.3].~A() (Implicit destructor)
 // CHECK-NEXT:   5: CFGScopeEnd(d)
-// CHECK-NEXT:   6: [B10.5].~A() (Implicit destructor)
-// CHECK-NEXT:   7: CFGScopeEnd(c)
 // CHECK-NEXT:   Preds (1): B5
 // CHECK-NEXT:   Succs (1): B2
 // CHECK:      [B4]
@@ -648,7 +653,7 @@
 // CHECK-NEXT:   9: [B10.7]
 // CHECK-NEXT:  10: [B10.9] (ImplicitCastExpr, UserDefinedConversion, int)
 // CHECK-NEXT:  11: [B10.10] (ImplicitCastExpr, IntegralToBoolean, _Bool)
-// CHECK-NEXT:   T: for (...; [B10.11]; )
+// CHECK-NEXT:   T: for (...; [B10.11]; ...)
 // CHECK-NEXT:   Preds (2): B2 B11
 // CHECK-NEXT:   Succs (2): B9 B1
 // CHECK:      [B11]
@@ -664,7 +669,7 @@
 // CHECK-NEXT:   Preds (2): B1 B4
 void test_for_jumps() {
   A a;
-  for (A b; A c = b; ) {
+  for (A b; A c = b; c.p) {
     A d;
     if (UV) break;
     if (UV) continue;
Index: clang/test/Analysis/lifetime-cfg-output.cpp
===================================================================
--- clang/test/Analysis/lifetime-cfg-output.cpp
+++ clang/test/Analysis/lifetime-cfg-output.cpp
@@ -529,13 +529,15 @@
 // CHECK-NEXT:    Preds (1): B4
 // CHECK-NEXT:    Succs (1): B0
 // CHECK:       [B2]
+// CHECK-NEXT:    1: b
+// CHECK-NEXT:    2: [B2.1].p
+// CHECK-NEXT:    3: [B4.4] (Lifetime ends)
 // CHECK-NEXT:    Preds (1): B3
 // CHECK-NEXT:    Succs (1): B4
 // CHECK:       [B3]
 // CHECK-NEXT:    1:  (CXXConstructExpr, A)
 // CHECK-NEXT:    2: A c;
 // CHECK-NEXT:    3: [B3.2] (Lifetime ends)
-// CHECK-NEXT:    4: [B4.4] (Lifetime ends)
 // CHECK-NEXT:    Preds (1): B4
 // CHECK-NEXT:    Succs (1): B2
 // CHECK:       [B4]
@@ -549,7 +551,7 @@
 // CHECK-NEXT:    8: [B4.6]
 // CHECK-NEXT:    9: [B4.8] (ImplicitCastExpr, UserDefinedConversion, int)
 // CHECK-NEXT:   10: [B4.9] (ImplicitCastExpr, IntegralToBoolean, _Bool)
-// CHECK-NEXT:    T: for (...; [B4.10]; )
+// CHECK-NEXT:    T: for (...; [B4.10]; ...)
 // CHECK-NEXT:    Preds (2): B2 B5
 // CHECK-NEXT:    Succs (2): B3 B1
 // CHECK:       [B5]
@@ -560,7 +562,7 @@
 // CHECK:       [B0 (EXIT)]
 // CHECK-NEXT:    Preds (1): B1
 void test_for_implicit_scope() {
-  for (A a; A b = a;)
+  for (A a; A b = a; b.p)
     A c;
 }
 
@@ -576,6 +578,9 @@
 // CHECK-NEXT:    Preds (2): B8 B10
 // CHECK-NEXT:    Succs (1): B0
 // CHECK:       [B2]
+// CHECK-NEXT:   1: c
+// CHECK-NEXT:   2: [B2.1].p
+// CHECK-NEXT:   3: [B10.4] (Lifetime ends)
 // CHECK-NEXT:    Preds (2): B3 B6
 // CHECK-NEXT:    Succs (1): B10
 // CHECK:       [B3]
@@ -583,7 +588,6 @@
 // CHECK-NEXT:    2: A e;
 // CHECK-NEXT:    3: [B3.2] (Lifetime ends)
 // CHECK-NEXT:    4: [B9.2] (Lifetime ends)
-// CHECK-NEXT:    5: [B10.4] (Lifetime ends)
 // CHECK-NEXT:    Preds (1): B5
 // CHECK-NEXT:    Succs (1): B2
 // CHECK:       [B4]
@@ -635,7 +639,7 @@
 // CHECK-NEXT:    8: [B10.6]
 // CHECK-NEXT:    9: [B10.8] (ImplicitCastExpr, UserDefinedConversion, int)
 // CHECK-NEXT:   10: [B10.9] (ImplicitCastExpr, IntegralToBoolean, _Bool)
-// CHECK-NEXT:    T: for (...; [B10.10]; )
+// CHECK-NEXT:    T: for (...; [B10.10]; ...)
 // CHECK-NEXT:    Preds (2): B2 B11
 // CHECK-NEXT:    Succs (2): B9 B1
 // CHECK:       [B11]
@@ -649,7 +653,7 @@
 // CHECK-NEXT:    Preds (2): B1 B4
 void test_for_jumps() {
   A a;
-  for (A b; A c = b;) {
+  for (A b; A c = b; c.p) {
     A d;
     if (UV)
       break;
Index: clang/test/Analysis/auto-obj-dtors-cfg-output.cpp
===================================================================
--- clang/test/Analysis/auto-obj-dtors-cfg-output.cpp
+++ clang/test/Analysis/auto-obj-dtors-cfg-output.cpp
@@ -1040,6 +1040,10 @@
 // CHECK-NEXT:   Preds (1): B4
 // CHECK-NEXT:   Succs (1): B0
 // CHECK:      [B2]
+// CHECK-NEXT:   1: b
+// CHECK-NEXT:   2: [B2.1].x
+// CHECK-NEXT:   3: ++[B2.2]
+// CHECK-NEXT:   4: [B4.4].~A() (Implicit destructor)
 // CHECK-NEXT:   Preds (1): B3
 // CHECK-NEXT:   Succs (1): B4
 // CHECK:      [B3]
@@ -1047,7 +1051,6 @@
 // ANALYZER-NEXT:   1:  (CXXConstructExpr, [B3.2], A)
 // CHECK-NEXT:   2: A c;
 // CHECK-NEXT:   3: [B3.2].~A() (Implicit destructor)
-// CHECK-NEXT:   4: [B4.4].~A() (Implicit destructor)
 // CHECK-NEXT:   Preds (1): B4
 // CHECK-NEXT:   Succs (1): B2
 // CHECK:      [B4]
@@ -1062,7 +1065,7 @@
 // CHECK-NEXT:   8: [B4.6]
 // CHECK-NEXT:   9: [B4.8] (ImplicitCastExpr, UserDefinedConversion, int)
 // CHECK:       10: [B4.9] (ImplicitCastExpr, IntegralToBoolean, _Bool)
-// CHECK-NEXT:   T: for (...; [B4.10]; )
+// CHECK-NEXT:   T: for (...; [B4.10]; ...)
 // CHECK-NEXT:   Preds (2): B2 B5
 // CHECK-NEXT:   Succs (2): B3 B1
 // CHECK:      [B5]
@@ -1074,7 +1077,7 @@
 // CHECK:      [B0 (EXIT)]
 // CHECK-NEXT:   Preds (1): B1
 void test_for_implicit_scope() {
-  for (A a; A b = a; )
+  for (A a; A b = a; ++b.x)
     A c;
 }
 
@@ -1144,6 +1147,10 @@
 // CHECK-NEXT:   Preds (2): B8 B10
 // CHECK-NEXT:   Succs (1): B0
 // CHECK:      [B2]
+// CHECK-NEXT:   1: c
+// CHECK-NEXT:   2: [B2.1].x
+// CHECK-NEXT:   3: ++[B2.2]
+// CHECK-NEXT:   4: [B10.4].~A() (Implicit destructor)
 // CHECK-NEXT:   Preds (2): B3 B6
 // CHECK-NEXT:   Succs (1): B10
 // CHECK:      [B3]
@@ -1152,7 +1159,6 @@
 // CHECK-NEXT:   2: A e;
 // CHECK-NEXT:   3: [B3.2].~A() (Implicit destructor)
 // CHECK-NEXT:   4: [B9.2].~A() (Implicit destructor)
-// CHECK-NEXT:   5: [B10.4].~A() (Implicit destructor)
 // CHECK-NEXT:   Preds (1): B5
 // CHECK-NEXT:   Succs (1): B2
 // CHECK:      [B4]
@@ -1206,7 +1212,7 @@
 // CHECK-NEXT:   8: [B10.6]
 // CHECK-NEXT:   9: [B10.8] (ImplicitCastExpr, UserDefinedConversion, int)
 // CHECK:       10: [B10.9] (ImplicitCastExpr, IntegralToBoolean, _Bool)
-// CHECK-NEXT:   T: for (...; [B10.10]; )
+// CHECK-NEXT:   T: for (...; [B10.10]; ...)
 // CHECK-NEXT:   Preds (2): B2 B11
 // CHECK-NEXT:   Succs (2): B9 B1
 // CHECK:      [B11]
@@ -1222,7 +1228,7 @@
 // CHECK-NEXT:   Preds (2): B1 B4
 void test_for_jumps() {
   A a;
-  for (A b; A c = b; ) {
+  for (A b; A c = b; ++c.x) {
     A d;
     if (UV) break;
     if (UV) continue;
Index: clang/lib/Analysis/CFG.cpp
===================================================================
--- clang/lib/Analysis/CFG.cpp
+++ clang/lib/Analysis/CFG.cpp
@@ -3511,6 +3511,11 @@
     Block = Succ = TransitionBlock = createBlock(false);
     TransitionBlock->setLoopTarget(F);
 
+
+    // Loop iteration (after increment) should end with destructor of Condition
+    // variable (if any).
+    addAutomaticObjHandling(ScopePos, LoopBeginScopePos, F);
+
     if (Stmt *I = F->getInc()) {
       // Generate increment code in its own basic block.  This is the target of
       // continue statements.
@@ -3530,8 +3535,6 @@
    ContinueJumpTarget = JumpTarget(Succ, ContinueScopePos);
    ContinueJumpTarget.block->setLoopTarget(F);
 
-    // Loop body should end with destructor of Condition variable (if any).
-   addAutomaticObjHandling(ScopePos, LoopBeginScopePos, F);
 
     // If body is not a compound statement create implicit scope
     // and add destructors.

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[PATCH] D155547: CPP-4580 Model lifetime of a variable declared in for condition in CFG correctly

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