Add safety comments to binder tests.

These will soon be required by a lint.

Bug: 290018030
Test: m rust
Change-Id: I807496ec5262145342ad9a40943094bfbe3cccc5

6 files changed, 140 insertions, 6 deletions

diff --git a/libs/binder/rust/src/parcel.rs b/libs/binder/rust/src/parcel.rs
index 0b0f9f9b61..3c615edbc0 100644
--- a/libs/binder/rust/src/parcel.rs
+++ b/libs/binder/rust/src/parcel.rs
@@ -723,6 +723,8 @@ fn test_read_write() {
 
     parcel.write(&1i32).unwrap();
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         parcel.set_data_position(start).unwrap();
     }
@@ -739,6 +741,8 @@ fn test_read_data() {
 
     parcel.write(&b"Hello, Binder!\0"[..]).unwrap();
     // Skip over string length
+    // SAFETY: str_start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(str_start).is_ok());
     }
@@ -747,42 +751,56 @@ fn test_read_data() {
 
     assert!(parcel.read::<bool>().unwrap());
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
 
     assert_eq!(parcel.read::<i8>().unwrap(), 72i8);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
 
     assert_eq!(parcel.read::<u16>().unwrap(), 25928);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
 
     assert_eq!(parcel.read::<i32>().unwrap(), 1819043144);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
 
     assert_eq!(parcel.read::<u32>().unwrap(), 1819043144);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
 
     assert_eq!(parcel.read::<i64>().unwrap(), 4764857262830019912);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
 
     assert_eq!(parcel.read::<u64>().unwrap(), 4764857262830019912);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
@@ -790,6 +808,8 @@ fn test_read_data() {
     assert_eq!(parcel.read::<f32>().unwrap(), 1143139100000000000000000000.0);
     assert_eq!(parcel.read::<f32>().unwrap(), 40.043392);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
@@ -797,6 +817,8 @@ fn test_read_data() {
     assert_eq!(parcel.read::<f64>().unwrap(), 34732488246.197815);
 
     // Skip back to before the string length
+    // SAFETY: str_start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(str_start).is_ok());
     }
@@ -810,15 +832,21 @@ fn test_utf8_utf16_conversions() {
     let start = parcel.get_data_position();
 
     assert!(parcel.write("Hello, Binder!").is_ok());
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
     assert_eq!(parcel.read::<Option<String>>().unwrap().unwrap(), "Hello, Binder!",);
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
 
     assert!(parcel.write("Embedded null \0 inside a string").is_ok());
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
@@ -826,6 +854,8 @@ fn test_utf8_utf16_conversions() {
         parcel.read::<Option<String>>().unwrap().unwrap(),
         "Embedded null \0 inside a string",
     );
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
@@ -840,6 +870,8 @@ fn test_utf8_utf16_conversions() {
     let s3 = "Some more text here.";
 
     assert!(parcel.write(&[s1, s2, s3][..]).is_ok());
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         assert!(parcel.set_data_position(start).is_ok());
     }
@@ -865,6 +897,8 @@ fn test_sized_write() {
 
     assert_eq!(parcel.get_data_position(), start + expected_len);
 
+    // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+    // made it any shorter since we got the position.
     unsafe {
         parcel.set_data_position(start).unwrap();
     }
@@ -884,6 +918,8 @@ fn test_append_from() {
     assert_eq!(4, parcel2.get_data_size());
     assert_eq!(Ok(()), parcel2.append_all_from(&parcel1));
     assert_eq!(8, parcel2.get_data_size());
+    // SAFETY: 0 is less than the current size of the parcel data buffer, because the parcel is not
+    // empty.
     unsafe {
         parcel2.set_data_position(0).unwrap();
     }
@@ -894,6 +930,8 @@ fn test_append_from() {
     assert_eq!(Ok(()), parcel2.append_from(&parcel1, 0, 2));
     assert_eq!(Ok(()), parcel2.append_from(&parcel1, 2, 2));
     assert_eq!(4, parcel2.get_data_size());
+    // SAFETY: 0 is less than the current size of the parcel data buffer, because the parcel is not
+    // empty.
     unsafe {
         parcel2.set_data_position(0).unwrap();
     }
@@ -902,6 +940,8 @@ fn test_append_from() {
     let mut parcel2 = Parcel::new();
     assert_eq!(Ok(()), parcel2.append_from(&parcel1, 0, 2));
     assert_eq!(2, parcel2.get_data_size());
+    // SAFETY: 0 is less than the current size of the parcel data buffer, because the parcel is not
+    // empty.
     unsafe {
         parcel2.set_data_position(0).unwrap();
     }
diff --git a/libs/binder/rust/src/parcel/parcelable.rs b/libs/binder/rust/src/parcel/parcelable.rs
index 038f198fce..9008a3cc0e 100644
--- a/libs/binder/rust/src/parcel/parcelable.rs
+++ b/libs/binder/rust/src/parcel/parcelable.rs
@@ -1087,6 +1087,8 @@ mod tests {
 
         assert!(custom.serialize(&mut parcel.borrowed()).is_ok());
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1109,6 +1111,8 @@ mod tests {
 
         assert!(bools.serialize(&mut parcel.borrowed()).is_ok());
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1118,6 +1122,8 @@ mod tests {
         assert_eq!(parcel.read::<u32>().unwrap(), 0);
         assert_eq!(parcel.read::<u32>().unwrap(), 0);
         assert_eq!(parcel.read::<u32>().unwrap(), 1);
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1133,12 +1139,17 @@ mod tests {
 
         assert!(parcel.write(&u8s[..]).is_ok());
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
 
         assert_eq!(parcel.read::<u32>().unwrap(), 4); // 4 items
         assert_eq!(parcel.read::<u32>().unwrap(), 0x752aff65); // bytes
+
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1148,18 +1159,25 @@ mod tests {
 
         let i8s = [-128i8, 127, 42, -117];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
 
         assert!(parcel.write(&i8s[..]).is_ok());
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
 
         assert_eq!(parcel.read::<u32>().unwrap(), 4); // 4 items
         assert_eq!(parcel.read::<u32>().unwrap(), 0x8b2a7f80); // bytes
+
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1169,10 +1187,14 @@ mod tests {
 
         let u16s = [u16::max_value(), 12_345, 42, 117];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(u16s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1182,6 +1204,9 @@ mod tests {
         assert_eq!(parcel.read::<u32>().unwrap(), 12345); // 12,345
         assert_eq!(parcel.read::<u32>().unwrap(), 42); // 42
         assert_eq!(parcel.read::<u32>().unwrap(), 117); // 117
+
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1192,10 +1217,14 @@ mod tests {
 
         let i16s = [i16::max_value(), i16::min_value(), 42, -117];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(i16s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1205,6 +1234,9 @@ mod tests {
         assert_eq!(parcel.read::<u32>().unwrap(), 0x8000); // i16::min_value()
         assert_eq!(parcel.read::<u32>().unwrap(), 42); // 42
         assert_eq!(parcel.read::<u32>().unwrap(), 0xff8b); // -117
+
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1215,10 +1247,14 @@ mod tests {
 
         let u32s = [u32::max_value(), 12_345, 42, 117];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(u32s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1228,6 +1264,9 @@ mod tests {
         assert_eq!(parcel.read::<u32>().unwrap(), 12345); // 12,345
         assert_eq!(parcel.read::<u32>().unwrap(), 42); // 42
         assert_eq!(parcel.read::<u32>().unwrap(), 117); // 117
+
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1238,10 +1277,14 @@ mod tests {
 
         let i32s = [i32::max_value(), i32::min_value(), 42, -117];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(i32s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1251,6 +1294,9 @@ mod tests {
         assert_eq!(parcel.read::<u32>().unwrap(), 0x80000000); // i32::min_value()
         assert_eq!(parcel.read::<u32>().unwrap(), 42); // 42
         assert_eq!(parcel.read::<u32>().unwrap(), 0xffffff8b); // -117
+
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1261,10 +1307,14 @@ mod tests {
 
         let u64s = [u64::max_value(), 12_345, 42, 117];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(u64s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1275,10 +1325,14 @@ mod tests {
 
         let i64s = [i64::max_value(), i64::min_value(), 42, -117];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(i64s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1289,10 +1343,14 @@ mod tests {
 
         let f32s = [std::f32::NAN, std::f32::INFINITY, 1.23456789, std::f32::EPSILON];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(f32s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1305,10 +1363,14 @@ mod tests {
 
         let f64s = [std::f64::NAN, std::f64::INFINITY, 1.234567890123456789, std::f64::EPSILON];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(f64s.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
@@ -1326,10 +1388,14 @@ mod tests {
 
         let strs = [s1, s2, s3, s4];
 
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
         assert!(strs.serialize(&mut parcel.borrowed()).is_ok());
+        // SAFETY: start is less than the current size of the parcel data buffer, because we haven't
+        // made it any shorter since we got the position.
         unsafe {
             assert!(parcel.set_data_position(start).is_ok());
         }
diff --git a/libs/binder/rust/tests/integration.rs b/libs/binder/rust/tests/integration.rs
index ca2cedc19d..c049b807df 100644
--- a/libs/binder/rust/tests/integration.rs
+++ b/libs/binder/rust/tests/integration.rs
@@ -545,6 +545,11 @@ mod tests {
     }
 
     fn get_expected_selinux_context() -> &'static str {
+        // SAFETY: The pointer we pass to `getcon` is valid because it comes from a reference, and
+        // `getcon` doesn't retain it after it returns. If `getcon` succeeds then `out_ptr` will
+        // point to a valid C string, otherwise it will remain null. We check for null, so the
+        // pointer we pass to `CStr::from_ptr` must be a valid pointer to a C string. There is a
+        // memory leak as we don't call `freecon`, but that's fine because this is just a test.
         unsafe {
             let mut out_ptr = ptr::null_mut();
             assert_eq!(selinux_sys::getcon(&mut out_ptr), 0);
diff --git a/libs/binder/rust/tests/ndk_rust_interop.rs b/libs/binder/rust/tests/ndk_rust_interop.rs
index 415ede1a7b..37f182eb08 100644
--- a/libs/binder/rust/tests/ndk_rust_interop.rs
+++ b/libs/binder/rust/tests/ndk_rust_interop.rs
@@ -28,10 +28,11 @@ use std::os::raw::{c_char, c_int};
 ///
 /// # Safety
 ///
-/// service_name must be a valid, non-null C-style string (null-terminated).
+/// service_name must be a valid, non-null C-style string (nul-terminated).
 #[no_mangle]
 pub unsafe extern "C" fn rust_call_ndk(service_name: *const c_char) -> c_int {
-    let service_name = CStr::from_ptr(service_name).to_str().unwrap();
+    // SAFETY: Our caller promises that service_name is a valid C string.
+    let service_name = unsafe { CStr::from_ptr(service_name) }.to_str().unwrap();
 
     // The Rust class descriptor pointer will not match the NDK one, but the
     // descriptor strings match so this needs to still associate.
@@ -85,10 +86,11 @@ impl IBinderRustNdkInteropTest for Service {
 ///
 /// # Safety
 ///
-/// service_name must be a valid, non-null C-style string (null-terminated).
+/// service_name must be a valid, non-null C-style string (nul-terminated).
 #[no_mangle]
 pub unsafe extern "C" fn rust_start_service(service_name: *const c_char) -> c_int {
-    let service_name = CStr::from_ptr(service_name).to_str().unwrap();
+    // SAFETY: Our caller promises that service_name is a valid C string.
+    let service_name = unsafe { CStr::from_ptr(service_name) }.to_str().unwrap();
     let service = BnBinderRustNdkInteropTest::new_binder(Service, BinderFeatures::default());
     match binder::add_service(service_name, service.as_binder()) {
         Ok(_) => StatusCode::OK as c_int,
diff --git a/libs/binder/rust/tests/parcel_fuzzer/parcel_fuzzer.rs b/libs/binder/rust/tests/parcel_fuzzer/parcel_fuzzer.rs
index 29bf92cb97..ce0f742934 100644
--- a/libs/binder/rust/tests/parcel_fuzzer/parcel_fuzzer.rs
+++ b/libs/binder/rust/tests/parcel_fuzzer/parcel_fuzzer.rs
@@ -105,9 +105,9 @@ fn do_read_fuzz(read_operations: Vec<ReadOperation>, data: &[u8]) {
     for operation in read_operations {
         match operation {
             ReadOperation::SetDataPosition { pos } => {
+                // Safety: Safe if pos is less than current size of the parcel.
+                // It relies on C++ code for bound checks
                 unsafe {
-                    // Safety: Safe if pos is less than current size of the parcel.
-                    // It relies on C++ code for bound checks
                     match parcel.set_data_position(pos) {
                         Ok(result) => result,
                         Err(e) => println!("error occurred while setting data position: {:?}", e),
diff --git a/libs/binder/rust/tests/serialization.rs b/libs/binder/rust/tests/serialization.rs
index 6220db4b28..8b04c76b33 100644
--- a/libs/binder/rust/tests/serialization.rs
+++ b/libs/binder/rust/tests/serialization.rs
@@ -113,11 +113,13 @@ fn on_transact(
         bindings::Transaction_TEST_BOOL => {
             assert!(parcel.read::<bool>()?);
             assert!(!parcel.read::<bool>()?);
+            // SAFETY: Just reading an extern constant.
             assert_eq!(parcel.read::<Vec<bool>>()?, unsafe { bindings::TESTDATA_BOOL });
             assert_eq!(parcel.read::<Option<Vec<bool>>>()?, None);
 
             reply.write(&true)?;
             reply.write(&false)?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_BOOL }[..])?;
             reply.write(&(None as Option<Vec<bool>>))?;
         }
@@ -125,14 +127,18 @@ fn on_transact(
             assert_eq!(parcel.read::<i8>()?, 0);
             assert_eq!(parcel.read::<i8>()?, 1);
             assert_eq!(parcel.read::<i8>()?, i8::max_value());
+            // SAFETY: Just reading an extern constant.
             assert_eq!(parcel.read::<Vec<i8>>()?, unsafe { bindings::TESTDATA_I8 });
+            // SAFETY: Just reading an extern constant.
             assert_eq!(parcel.read::<Vec<u8>>()?, unsafe { bindings::TESTDATA_U8 });
             assert_eq!(parcel.read::<Option<Vec<i8>>>()?, None);
 
             reply.write(&0i8)?;
             reply.write(&1i8)?;
             reply.write(&i8::max_value())?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_I8 }[..])?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_U8 }[..])?;
             reply.write(&(None as Option<Vec<i8>>))?;
         }
@@ -140,12 +146,14 @@ fn on_transact(
             assert_eq!(parcel.read::<u16>()?, 0);
             assert_eq!(parcel.read::<u16>()?, 1);
             assert_eq!(parcel.read::<u16>()?, u16::max_value());
+            // SAFETY: Just reading an extern constant.
             assert_eq!(parcel.read::<Vec<u16>>()?, unsafe { bindings::TESTDATA_CHARS });
             assert_eq!(parcel.read::<Option<Vec<u16>>>()?, None);
 
             reply.write(&0u16)?;
             reply.write(&1u16)?;
             reply.write(&u16::max_value())?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_CHARS }[..])?;
             reply.write(&(None as Option<Vec<u16>>))?;
         }
@@ -153,12 +161,14 @@ fn on_transact(
             assert_eq!(parcel.read::<i32>()?, 0);
             assert_eq!(parcel.read::<i32>()?, 1);
             assert_eq!(parcel.read::<i32>()?, i32::max_value());
+            // SAFETY: Just reading an extern constant.
             assert_eq!(parcel.read::<Vec<i32>>()?, unsafe { bindings::TESTDATA_I32 });
             assert_eq!(parcel.read::<Option<Vec<i32>>>()?, None);
 
             reply.write(&0i32)?;
             reply.write(&1i32)?;
             reply.write(&i32::max_value())?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_I32 }[..])?;
             reply.write(&(None as Option<Vec<i32>>))?;
         }
@@ -166,12 +176,14 @@ fn on_transact(
             assert_eq!(parcel.read::<i64>()?, 0);
             assert_eq!(parcel.read::<i64>()?, 1);
             assert_eq!(parcel.read::<i64>()?, i64::max_value());
+            // SAFETY: Just reading an extern constant.
             assert_eq!(parcel.read::<Vec<i64>>()?, unsafe { bindings::TESTDATA_I64 });
             assert_eq!(parcel.read::<Option<Vec<i64>>>()?, None);
 
             reply.write(&0i64)?;
             reply.write(&1i64)?;
             reply.write(&i64::max_value())?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_I64 }[..])?;
             reply.write(&(None as Option<Vec<i64>>))?;
         }
@@ -179,12 +191,14 @@ fn on_transact(
             assert_eq!(parcel.read::<u64>()?, 0);
             assert_eq!(parcel.read::<u64>()?, 1);
             assert_eq!(parcel.read::<u64>()?, u64::max_value());
+            // SAFETY: Just reading an extern constant.
             assert_eq!(parcel.read::<Vec<u64>>()?, unsafe { bindings::TESTDATA_U64 });
             assert_eq!(parcel.read::<Option<Vec<u64>>>()?, None);
 
             reply.write(&0u64)?;
             reply.write(&1u64)?;
             reply.write(&u64::max_value())?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_U64 }[..])?;
             reply.write(&(None as Option<Vec<u64>>))?;
         }
@@ -192,10 +206,12 @@ fn on_transact(
             assert_eq!(parcel.read::<f32>()?, 0f32);
             let floats = parcel.read::<Vec<f32>>()?;
             assert!(floats[0].is_nan());
+            // SAFETY: Just reading an extern constant.
             assert_eq!(floats[1..], unsafe { bindings::TESTDATA_FLOAT }[1..]);
             assert_eq!(parcel.read::<Option<Vec<f32>>>()?, None);
 
             reply.write(&0f32)?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_FLOAT }[..])?;
             reply.write(&(None as Option<Vec<f32>>))?;
         }
@@ -203,10 +219,12 @@ fn on_transact(
             assert_eq!(parcel.read::<f64>()?, 0f64);
             let doubles = parcel.read::<Vec<f64>>()?;
             assert!(doubles[0].is_nan());
+            // SAFETY: Just reading an extern constant.
             assert_eq!(doubles[1..], unsafe { bindings::TESTDATA_DOUBLE }[1..]);
             assert_eq!(parcel.read::<Option<Vec<f64>>>()?, None);
 
             reply.write(&0f64)?;
+            // SAFETY: Just reading an extern constant.
             reply.write(&unsafe { bindings::TESTDATA_DOUBLE }[..])?;
             reply.write(&(None as Option<Vec<f64>>))?;
         }
@@ -216,14 +234,17 @@ fn on_transact(
             let s: Option<String> = parcel.read()?;
             assert_eq!(s, None);
             let s: Option<Vec<Option<String>>> = parcel.read()?;
+            // SAFETY: Just reading an extern constant.
             for (s, expected) in s.unwrap().iter().zip(unsafe { bindings::TESTDATA_STRS }.iter()) {
                 let expected =
+            // SAFETY: Just reading an extern constant.
                     unsafe { expected.as_ref().and_then(|e| CStr::from_ptr(e).to_str().ok()) };
                 assert_eq!(s.as_deref(), expected);
             }
             let s: Option<Vec<Option<String>>> = parcel.read()?;
             assert_eq!(s, None);
 
+            // SAFETY: Just reading an extern constant.
             let strings: Vec<Option<String>> = unsafe {
                 bindings::TESTDATA_STRS
                     .iter()