| Issue |
123545
|
| Summary |
__builtin_launder complains about type completeness
|
| Labels |
c++17,
clang:frontend,
diverges-from:gcc,
diverges-from:msvc,
diverges-from:edg
|
| Assignees |
|
| Reporter |
hubert-reinterpretcast
|
`std::launder` does not require that the type pointed to is complete. See https://wg21.link/ptr.launder.
Clang refuses to compile the following:
```cpp
#include <new>
struct A;
A *h(A *p) { return std::launder(p); }
```
which becomes (with multiple C++ standard libraries):
```cpp
struct A;
A *h(A *p) { return __builtin_launder(p); }
```
Online compiler link: https://godbolt.org/z/8KG98zaxW
### SOURCE (`<stdin>`):
```cpp
struct A;
A *h(A *p) { return __builtin_launder(p); }
```
### COMPILER INVOCATION:
```
clang++ -fsyntax-only -std=c++17 -xc++ -
```
### ACTUAL COMPILER OUTPUT:
```
<stdin>:2:21: error: incomplete type 'A' where a complete type is required
2 | A *h(A *p) { return __builtin_launder(p); }
| ^
<stdin>:1:8: note: forward declaration of 'A'
1 | struct A;
| ^
1 error generated.
```
### EXPECTED COMPILER OUTPUT:
(clean compile)
### COMPILER VERSION INFO (`clang++ -v`):
```
clang version 20.0.0git (https://github.com/llvm/llvm-project.git dd42651295d0e1566b34104b007ad19865c57fcc)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/wandbox/clang-head/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/13
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/14
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/14
Candidate multilib: .;@m64
Selected multilib: .;@m64
```
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