llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Pavel Samolysov (samolisov)
<details>
<summary>Changes</summary>
When clang compiles the following expression:
```c++
return A{B{"Move Ctor"}};
```
(where `B` is a base class for `A`), it adds a call to the move constructor of
`B`. When the code is changed to...
```c++
return A{{"No Move Ctor"}};
```
... a move constructor is invoked neither for `A` nor for `B`.
The lit test demonstrates the difference in the generated AST.
---
Full diff: https://github.com/llvm/llvm-project/pull/97164.diff
1 Files Affected:
- (added) clang/test/AST/explicit-base-class-move-cntr.cpp (+43)
``````````diff
diff --git a/clang/test/AST/explicit-base-class-move-cntr.cpp
b/clang/test/AST/explicit-base-class-move-cntr.cpp
new file mode 100644
index 0000000000000..b9b591ebc79d7
--- /dev/null
+++ b/clang/test/AST/explicit-base-class-move-cntr.cpp
@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 -ast-dump -fblocks %s | FileCheck -strict-whitespace %s
+
+struct ExplicitBase {
+ explicit ExplicitBase(const char *) { }
+ ExplicitBase(const ExplicitBase &) {}
+ ExplicitBase(ExplicitBase &&) {}
+ ExplicitBase &operator=(const ExplicitBase &) { return *this; }
+ ExplicitBase &operator=(ExplicitBase &&) { return *this; }
+ ~ExplicitBase() { }
+};
+
+struct Derived1 : ExplicitBase {};
+
+Derived1 makeDerived1() {
+ // CHECK: FunctionDecl 0x{{[^ ]*}} <line:[[@LINE-1]]:1,
line:{{[^:]*}}:1> line:[[@LINE-1]]:10 makeDerived1 'Derived1 ()'
+ // CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:{{[^ ^,]+}}, line:{{[^:]*}}:1
+ // CHECK-NEXT: ReturnStmt 0x{{[^ ]*}} <line:[[@LINE+6]]:3, col:{{[0-9]+}}>
+ // CHECK-DAG: MaterializeTemporaryExpr 0x{{[^ ]*}} <col:{{[0-9]+}},
col:{{[0-9]+}}> 'ExplicitBase' xvalue
+ // CHECK-NEXT: CXXBindTemporaryExpr 0x[[TEMP:[^ ]*]] <col:{{[0-9]+}},
col:{{[0-9]+}}> 'ExplicitBase' (CXXTemporary 0x[[TEMP]])
+ // CHECK-NEXT: CXXTemporaryObjectExpr 0x{{[^ ]*}} <col:{{[0-9]+}},
col:{{[0-9]+}}> 'ExplicitBase' 'void (const char *)' list
+ // CHECK-NEXT: ImplicitCastExpr 0x{{[^ ]*}} <col:{{[0-9]+}}> 'const char *'
<ArrayToPointerDecay>
+ // CHECK-NEXT: StringLiteral 0x{{[^ ]*}} <col:{{[0-9]+}}> 'const char[10]'
lvalue "Move Ctor"
+ return Derived1{ExplicitBase{"Move Ctor"}};
+}
+
+struct ImplicitBase {
+ ImplicitBase(const char *) { }
+ ImplicitBase(const ImplicitBase &) {}
+ ImplicitBase(ImplicitBase &&) {}
+ ImplicitBase &operator=(const ImplicitBase &) { return *this; }
+ ImplicitBase &operator=(ImplicitBase &&) { return *this; }
+ ~ImplicitBase() { }
+};
+
+struct Derived2 : ImplicitBase {};
+
+Derived2 makeDerived2() {
+ // CHECK: FunctionDecl 0x{{[^ ]*}} <line:[[@LINE-1]]:1,
line:{{[^:]*}}:1> line:[[@LINE-1]]:10 makeDerived2 'Derived2 ()'
+ // CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:{{[^ ^,]+}}, line:{{[^:]*}}:1
+ // CHECK-NEXT: ReturnStmt 0x{{[^ ]*}} <line:[[@LINE+2]]:3, col:{{[0-9]+}}>
+ // CHECK-NOT: MaterializeTemporaryExpr 0x{{[^ ]*}} <col:{{[0-9]+}},
col:{{[0-9]+}}> 'ImplicitBase' xvalue
+ return Derived2{{"No Ctor"}};
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/97164
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