FyroxEngine/Fyrox · warning

Failed to copy file to the folder. Reason

Error message

Failed to copy {} file to the {} folder. Reason: {:?}

What it means

Logged warning in fyrox-build-tools' PC export when std::fs::copy fails while copying the game binary or its dependencies into the destination export folder. Like the Android variant, it is non-fatal but leaves the export incomplete. The io::Error is included in the message.

Solutions

1. Close the running game instance that locks the destination binary
2. Create the destination folder with fs::create_dir_all before exporting
3. Run the export with write permission for the destination (avoid copying into protected system dirs)
4. Whitelist the build/export directory in antivirus software and retry

Example fix

// before
Log::warn(format!("Failed to copy {} ...", path.display()));
// after
fs::create_dir_all(&destination_folder)?;
fs::copy(&path, &dst).map_err(|e| anyhow!("copy {} -> {}: {e}", path.display(), dst.display()))?;

assert!(path.is_file(), "source binary missing: {}", path.display());
fs::create_dir_all(&destination_folder)?;

fs::copy(&path, &dst).or_else(|e| {
    Log::warn(format!("copy {} failed: {e}", path.display()));
    Err(e)
})?;

When it happens

Trigger: copy_binaries in fyrox-build-tools/src/export/pc.rs calls fs::copy for each discovered binary; the Err arm logs this with path, destination folder, and error.

Common situations: Destination exe locked because the game is still running, destination folder missing, permission denied in Program Files-like locations, antivirus quarantining the freshly built exe.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• Failed to copy file to the folder. Reason
• unknown target platform
• Attempt to get reference to resource data which failed to…
• Invalid path
• An error occurred when reading data from socket

AI-assisted analysis of FyroxEngine/Fyrox@76c91aad8e (2026-09-10). Data as JSON: /api/errors/13ae6a23416c943f. Report an issue: GitHub.

Appendix: source

Thrown at fyrox-build-tools/src/export/pc.rs:75

        if let Some(stem) = entry.path().file_stem() {
            if stem == OsStr::new(package_name) {
                binary_paths.push(entry.path());
            }
        }
    }
    for path in binary_paths {
        if let Some(file_name) = path.file_name() {
            match fs::copy(&path, destination_folder.join(file_name)) {
                Ok(_) => {
                    Log::info(format!(
                        "{} was successfully copied to the {} folder.",
                        path.display(),
                        destination_folder.display()
                    ));
                }
                Err(err) => {
                    Log::warn(format!(
                        "Failed to copy {} file to the {} folder. Reason: {:?}",
                        path.display(),
                        destination_folder.display(),
                        err
                    ));
                }
            }
        }
    }

    Ok(())
}

pub fn run_build(destination_folder: &Path, package_name: &str) {
    #[allow(unused_mut)]
    let mut path = destination_folder.join(package_name);
    #[cfg(windows)]
    {

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