sxyazi/yazi · error

Failed to get the C string from CFString

Error message

Failed to get the C string from CFString

What it means

CFString::os_string extracts the string's bytes with CFStringGetCString using UTF-8; the bails fires when that function returns 0, meaning the conversion to a C string failed. The CFString content could not be represented (or the buffer was insufficient), so no OsString can be produced.

Source

Thrown at yazi-ffi/src/cf_string.rs:39

		if key.is_null() {
			bail!("Allocation failed while creating CFString");
		}
		Ok(Self(key))
	}

	fn len(&self) -> usize { unsafe { CFStringGetLength(self.0) as _ } }

	pub(crate) fn os_string(&self) -> Result<OsString> {
		let len = self.len();
		let capacity =
			unsafe { CFStringGetMaximumSizeForEncoding(len as _, kCFStringEncodingUTF8) } + 1;

		let mut out: Vec<u8> = Vec::with_capacity(capacity as usize);
		let result = unsafe {
			CFStringGetCString(self.0, out.as_mut_ptr().cast(), capacity, kCFStringEncodingUTF8)
		};
		if result == 0 {
			bail!("Failed to get the C string from CFString");
		}

		unsafe { out.set_len(strlen(out.as_ptr().cast())) };
		out.shrink_to_fit();
		Ok(OsString::from_vec(out))
	}
}

impl Deref for CFString {
	type Target = CFStringRef;

	fn deref(&self) -> &Self::Target { &self.0 }
}

impl Drop for CFString {
	fn drop(&mut self) { unsafe { CFRelease(self.0 as _) }; }
}

View on GitHub (pinned to 5f901b886b)

Solutions

1. Fall back to CFStringGetCStringPtr or CFStringGetBytes with lossy conversion instead of strict UTF-8 C-string extraction.
2. Verify the capacity passed to CFStringGetCString accounts for the NUL terminator (len + 1).
3. Inspect the source data for non-UTF-8 or embedded-NUL content and sanitize it upstream.

// Before extraction you cannot easily validate encoding; guard by checking length fits the buffer
let capacity = (unsafe { CFStringGetLength(s.0) } + 1) as usize;
// if capacity exceeds what os_string allocates, expect failure

let name = cf_string.os_string().unwrap_or_else(|_| OsString::from("<unreadable>"));

When it happens

Trigger: Calling os_string() on a CFString whose contents are not valid UTF-8 (e.g. legacy MacRoman filenames) or whose length exceeds the computed capacity, causing CFStringGetCString to fail.

Common situations: Reading macOS metadata strings that contain legacy non-UTF-8 encodings from old files or Finder aliases; corrupted metadata blobs; strings with embedded NUL bytes.

Related errors

• Cannot take a null pointer
• Cannot get the value for the key `{key}`
• Allocation failed while creating CFString
• Cannot create a disk arbitration session
• Cannot get the IO matching services

AI-assisted analysis of sxyazi/yazi@5f901b886b (2026-09-02). Data as JSON: /api/errors/0df7fb607bd2da5b. Report an issue: GitHub.