| Issue |
138939
|
| Summary |
Clang++ rejects try-catch in discarded if constexpr branch with -fno-exceptions
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
zerhud
|
**Summary**:
Clang incorrectly rejects code containing a `try-catch` block inside a discarded `if constexpr` branch when compiled with `-fno-exceptions`. The `try-catch` block should not be evaluated, as it is excluded at compile-time, but Clang emits an error: `cannot use 'try' with exceptions disabled`.
**Steps to Reproduce**:
1. Create a file `test.cpp` with the following code:
```cpp
template<auto enable> void foo(auto&& fnc) {
if constexpr(enable) try{ fnc(); } catch(...){}
else fnc();
}
int main(int, char**) {
foo<false>([]{});
}
```
2. Compile with:
```bash
clang++ -std=c++20 -fno-exceptions -c test.cpp
```
3. Alternatively, see the issue on [Godbolt](https://godbolt.org/z/3ecnde5z4): https://godbolt.org/z/3ecnde5z4
**Actual Results**:
```
test.cpp:2:25: error: cannot use 'try' with exceptions disabled
if constexpr(enable) try{ fnc(); } catch(...){}
^
1 error generated.
```
**Expected Results**:
The code should compile successfully, as the `try-catch` block is in a discarded `if constexpr` branch and should not be evaluated.
**Additional Information**:
- The code compiles successfully with GCC
- A not called template function with try-catch block rejected too ([Godbolt](https://godbolt.org/z/4nb3vcYTo))
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