cross-rs/cross · error

Could not get UserName.

Error message

Could not get UserName.

What it means

This error is thrown by the Windows `username()` helper when the Win32 API `GetUserNameW` fails (returns 0). The function queries the current user's login name for toolchain/directory identification and converts it to a Rust String; failure means Windows refused the credential query. The error aborts the lookup rather than guessing a fallback name.

Solutions

1. Verify the process runs under a real user session (not an empty-token service/impersonation context).
2. Check Windows event logs / `whoami` in the same context to confirm the OS can resolve the username.
3. If username is unavailable by design, prefer the `Ok(None)` code path (before this call) instead of forcing the lookup.
4. Retry in an environment with a loaded user profile (e.g. interactive logon, `psexec -i`, or configured service account with profile).

Example fix

// before
let name = username()?; // bails with "Could not get UserName."
// after
let name = match username() {
    Ok(Some(n)) => n,
    Ok(None) => fallback_default_name(),
    Err(e) => fallback_default_name(), // use a default dir name instead of failing
};

#[cfg(windows)]
fn can_query_username() -> bool {
    // username() returns Ok(None) *before* GetUserNameW is tried when
    // the buffer size query fails, so only a real call failure hits the error.
    std::env::var("USERNAME").is_ok() || whoami_check()
}

fn has_user_context() -> bool {
    std::env::var("USERNAME").is_ok()
}

When it happens

Trigger: Calling `username()` on Windows when `GetUserNameW` returns 0 — e.g. when no user token is associated with the process (service session, broken profile, extremely small buffer) or the API call is otherwise rejected.

Common situations: Running under a Windows service or scheduled task with no interactive user; corrupted user profile where the access token has no username; running in restricted sandboxes/CI containers that strip user context.

Understand the failure class

Background: "environment variable is not set" and "Missing keys in environment" errors: what missing required env var messages mean and how to fix them — this error's family across 28 libraries.

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AI-assisted analysis of cross-rs/cross@8c1a8aa4b6 (2026-09-13). Data as JSON: /api/errors/6bf1bbcc6b908475. Report an issue: GitHub.

Appendix: source

Thrown at src/id.rs:48

#[cfg(target_os = "windows")]
pub fn username() -> Result<Option<String>> {
    use std::ptr;

    use winapi::um::winbase::GetUserNameW;

    unsafe {
        let mut size = 0;
        GetUserNameW(ptr::null_mut(), &mut size);

        if size == 0 {
            return Ok(None);
        }

        let mut username = Vec::with_capacity(size as usize);

        if GetUserNameW(username.as_mut_ptr(), &mut size) == 0 {
            eyre::bail!("Could not get UserName.");
        }

        // Remove null terminator.
        username.set_len((size - 1) as usize);

        Ok(Some(String::from_utf16_lossy(&username)))
    }
}

#[cfg(not(target_os = "windows"))]
pub fn username() -> Result<Option<String>> {
    let name = unsafe {
        Errno::clear();

        let passwd = libc::getpwuid(Uid::current().as_raw());

        if passwd.is_null() {
            let errno = Errno::last_raw();

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