current_exe return \\\?\\ prefix symbols

[bmiyuan]

Background：
I use current_exe() on Windows, but std::env::current_exe() return "\\?\D:\code\test\target\debug\test.exe"

Steps to Reproduce:
fn main() {
let program_dir=std::env::current_exe().unwrap();
println!("program_dir {:?}",&program_dir);
}

Rust Version:
rustc 1.62.1 (e092d0b 2022-07-16)

Expected Behavior:
I would expect to get:
"D:\code\test\target\debug\test.exe"

Actual Behavior:
"\\?\D:\code\test\target\debug\test.exe"

[bjorn3]

libstd uses GetModuleFileNameW to get the executable name:

rust/library/std/src/sys/windows/os.rs

Line 239 in e50ff9b

|buf, sz| unsafe { c::GetModuleFileNameW(ptr::null_mut(), buf, sz) },

This function seems to indeed return \\?\ prefixed paths. libstd can handle these paths just fine, and they are mandatory when the path gets too long. Not a windows expert, but I did say not a bug.

[the8472]

These are valid paths. If you need to pass them to an application which can't handle them you can try using the dunce crate, but it's not guaranteed that this will work for all paths because verbatim paths can refer to files that are unnamable by non-verbatim ones. Not only due to lengths but also due to some parsing that happens.

[mati865]

There is also unstable absolute function.

[nagisa]

Largely a…

Duplicate of #59117

[Zoxc]

#59117 seems to be a separate issue about turning paths absolute.