| Issue |
208078
|
| Summary |
[clang-tidy] `bugprone-misplaced-widening-cast` shouldn't warn on correct `constexpr` values
|
| Labels |
|
| Assignees |
|
| Reporter |
Jacobfaib
|
Consider the following (https://godbolt.org/z/5jTTWh9cb):
```c++
#include <cstddef>
void bar(std::size_t);
void foo() {
constexpr int x = 256;
bar(static_cast<std::size_t>(x * 2));
}
```
The `static_cast<std::size_t>` is indeed pointless if the intent was to avoid overflow of `int` before passing to `bar()`. The correct form would be
```c++
static_cast<std::size_t>(x) * 2
```
However in this case, because `x` is `constexpr`, the compiler (and by extension `clang-tidy`) can compute the value of `x * 2` and see that it never overflows. Even if the cast is pointless, the code is still provably correct as written.
In this case `clang-tidy` should suppress the `misplaced-widening-cast` diagnostic, because otherwise it is pointless churn. There is no "cast" occurring anyways, the compiler will just constant fold the value to `size_t` anyways.
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