| Issue |
139818
|
| Summary |
[clang] constant evaluation of `for` loop does not run destructor for condition variable
|
| Labels |
good first issue,
clang:frontend,
accepts-invalid,
c++23
|
| Assignees |
|
| Reporter |
zygoloid
|
If a condition variable is declared in the second clause of a three-clause `for` loop, clang doesn't destroy it when constant-evaluating the loop. For example:
```c++
struct X {
constexpr ~X() noexcept(false) { throw "oops"; }
constexpr operator bool() {
return b;
}
bool b;
};
constexpr bool f() {
for (bool b = false; X x = {b}; b = true) {}
return true;
}
static_assert(f());
```
Clang treats this as constant, but the destructor for `x` throws an exception.
It looks like the problem is that we fail to call `IterScope.destroy()` [here](https://github.com/llvm/llvm-project/blob/5f41928689125667cf645835fa9fefee97511d8a/clang/lib/AST/ExprConstant.cpp#L5742), when terminating a loop iteration because the condition evaluated to `false`.
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