| Issue |
89388
|
| Summary |
`scoped_lock` constructor could be `nodiscard` like in `libstdc++`
|
| Labels |
enhancement,
libc++
|
| Assignees |
|
| Reporter |
steakhal
|
Consider this [code](https://godbolt.org/z/fror15jfd):
```c++
#include <mutex>
int num;
std::mutex m;
void top() {
if (std::scoped_lock{m}; num > 10) { // no-warning :(
num = 1;
}
if (std::lock_guard{m}; num > 11) { // warn: nodiscard
num = 2;
}
}
```
The constructor of `std::scoped_lock` should have the `[[nodiscard]]` attribute to catch mistakes like the one in the example, creating a temporary `scoped_lock` object and leaving the access of the global variable unguarded.
If we use libstdc++, we get the following warning `ignoring temporary created by a constructor declared with 'nodiscard' attribute [-Wunused-value]`. Maybe we could also have this `nodiscard` attribute too.
Note that for instance `lock_guard` works as expected, and has the ``nodiscard` attribute.
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