https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126730
Bug ID: 126730
Summary: `std::filesystem::hash_value` returns different hash
value for paths that compare equal
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: 121539739 at qq dot com
Target Milestone: ---
[fs.path.nonmember] says:
> `size_t hash_value(const path& p) noexcept; `
>
> *Returns*: A hash value for the path `p`. If for two paths, `p1 == p2`
> then `hash_value(p1) == hash_value(p2)`.
```cpp
#include <cassert>
#include <filesystem>
namespace fs = std::filesystem;
int main() {
fs::path a{ "/" }, b{ "//" }, c{ "///" };
assert(a == b); // ok
assert(b == c); // ok
assert(fs::hash_value(a) == fs::hash_value(b)); // fail
assert(fs::hash_value(b) == fs::hash_value(c)); // fail
}
```
`a`, `b` and `c` compare equal, but their `hash_value`s diverge.
libc++ and MS STL both agree these paths compare equal and both give equal
hashes.
detailed: https://godbolt.org/z/Gh66jnvzK
