feat(coreaudio): add macOS system audio permission helpers

Cargo.toml

@@ -139,6 +139,9 @@ objc2 = { version = "0.6" }
 
 [target.'cfg(target_os = "macos")'.dependencies]
 jack = { version = "0.13", optional = true }
+libloading = "0.8"
+block2 = "0.6"
+objc2-core-foundation = "0.3"
 
 [target.'cfg(target_os = "ios")'.dependencies]
 objc2-avf-audio = { version = "0.3", default-features = false, features = [

src/host/coreaudio/macos/mod.rs

@@ -20,6 +20,7 @@ use property_listener::AudioObjectPropertyListener;
 mod device;
 pub mod enumerate;
 mod loopback;
+pub mod permissions;
 mod property_listener;
 pub use device::Device;
 

src/host/coreaudio/macos/permissions.rs

@@ -0,0 +1,66 @@
+//! macOS system audio recording permission helpers.
+//!
+//! These functions check and request the "System Audio Recording" permission
+//! (`kTCCServiceAudioCapture`) via the private TCC framework — required for
+//! loopback recording via [`default_output_device`](super::enumerate::default_output_device).
+
+use block2::StackBlock;
+use libloading::{Library, Symbol};
+use objc2_core_foundation::{CFRetained, CFString};
+use std::ffi::c_void;
+
+const TCC_FRAMEWORK: &str = "/System/Library/PrivateFrameworks/TCC.framework/Versions/A/TCC";
+const TCC_SERVICE: &str = "kTCCServiceAudioCapture";
+
+fn load_tcc() -> Option<Library> {
+    unsafe { Library::new(TCC_FRAMEWORK) }.ok()
+}
+
+fn tcc_service() -> CFRetained<CFString> {
+    CFString::from_str(TCC_SERVICE)
+}
+
+/// Request system audio recording permission, showing the system prompt if needed.
+///
+/// **Blocking** — does not return until the user responds.
+/// Returns `false` immediately (without showing UI) if previously denied —
+/// call [`open_system_audio_settings`] in that case.
+pub fn request_system_audio_permission() -> bool {
+    let Some(lib) = load_tcc() else { return false };
+    unsafe {
+        let Ok(request_fn): Result<
+            Symbol<unsafe extern "C" fn(*const c_void, *const c_void, *const c_void)>,
+            _,
+        > = lib.get(b"TCCAccessRequest\0") else {
+            return false;
+        };
+
+        let (tx, rx) = std::sync::mpsc::sync_channel::<bool>(1);
+        // Store as usize (Copy) so TCC's internal block memcpy doesn't double-drop the sender.
+        let tx_ptr = Box::into_raw(Box::new(tx)) as usize;
+
+        let completion = StackBlock::new(move |granted: u8| {
+            let tx = Box::from_raw(tx_ptr as *mut std::sync::mpsc::SyncSender<bool>);
+            tx.send(granted != 0).ok();
+        });
+
+        let service = tcc_service();
+        request_fn(
+            &*service as *const _ as *const c_void,
+            std::ptr::null(),
+            &completion as *const _ as *const c_void,
+        );
+
+        rx.recv().unwrap_or(false)
+    }
+}
+
+/// Open Privacy & Security > System Audio Recording in System Settings.
+///
+/// Call this when [`request_system_audio_permission`] returns `false` (previously denied).
+pub fn open_system_audio_settings() {
+    std::process::Command::new("open")
+        .arg("x-apple.systempreferences:com.apple.settings.PrivacySecurity.extension?Privacy_AudioCapture")
+        .spawn()
+        .ok();
+}

src/host/coreaudio/mod.rs

@@ -15,7 +15,7 @@ use crate::{BackendSpecificError, SampleFormat, StreamConfig};
 #[cfg(target_os = "ios")]
 mod ios;
 #[cfg(target_os = "macos")]
-mod macos;
+pub mod macos;
 
 #[cfg(target_os = "ios")]
 #[allow(unused_imports)]

src/lib.rs

@@ -183,6 +183,10 @@ pub use device_description::{
     DeviceDescription, DeviceDescriptionBuilder, DeviceDirection, DeviceType, InterfaceType,
 };
 pub use error::*;
+#[cfg(target_os = "macos")]
+pub use host::coreaudio::macos::permissions::{
+    open_system_audio_settings, request_system_audio_permission,
+};
 pub use platform::{
     available_hosts, default_host, host_from_id, Device, Devices, Host, HostId, Stream,
     SupportedInputConfigs, SupportedOutputConfigs, ALL_HOSTS,

src/platform/mod.rs

@@ -748,6 +748,11 @@ mod platform_impl {
 
 #[cfg(any(target_os = "macos", target_os = "ios"))]
 mod platform_impl {
+    #[cfg(target_os = "macos")]
+    #[cfg_attr(docsrs, doc(cfg(target_os = "macos")))]
+    pub use crate::host::coreaudio::macos::permissions::{
+        open_system_audio_settings, request_system_audio_permission,
+    };
     #[cfg_attr(docsrs, doc(cfg(any(target_os = "macos", target_os = "ios"))))]
     pub use crate::host::coreaudio::Host as CoreAudioHost;
     #[cfg(all(feature = "jack", target_os = "macos"))]