diff --git a/api/arceos_posix_api/src/imp/fs.rs b/api/arceos_posix_api/src/imp/fs.rs
index 9c88081c38..0e877e6081 100644
--- a/api/arceos_posix_api/src/imp/fs.rs
+++ b/api/arceos_posix_api/src/imp/fs.rs
@@ -183,6 +183,7 @@ pub unsafe fn sys_lstat(path: *const c_char, buf: *mut ctypes::stat) -> ctypes::
 }
 
 /// Get the path of the current directory.
+#[allow(clippy::unnecessary_cast)] // `c_char` is either `i8` or `u8`
 pub fn sys_getcwd(buf: *mut c_char, size: usize) -> *mut c_char {
     debug!("sys_getcwd <= {:#x} {}", buf as usize, size);
     syscall_body!(sys_getcwd, {
diff --git a/examples/shell/src/main.rs b/examples/shell/src/main.rs
index 301033c4fd..56e999bc99 100644
--- a/examples/shell/src/main.rs
+++ b/examples/shell/src/main.rs
@@ -11,8 +11,8 @@ fn path_to_str(path: &impl AsRef<std::ffi::OsStr>) -> &str {
 }
 
 #[cfg(feature = "axstd")]
-fn path_to_str(path: &std::string::String) -> &str {
-    path.as_str()
+fn path_to_str(path: &str) -> &str {
+    path
 }
 
 mod cmd;
diff --git a/modules/axhal/src/cpu.rs b/modules/axhal/src/cpu.rs
index 14feeaa39f..ae35d3654b 100644
--- a/modules/axhal/src/cpu.rs
+++ b/modules/axhal/src/cpu.rs
@@ -57,21 +57,19 @@ pub fn current_task_ptr<T>() -> *const T {
 /// The given `ptr` must be pointed to a valid task structure.
 #[inline]
 pub unsafe fn set_current_task_ptr<T>(ptr: *const T) {
-    unsafe {
-        #[cfg(target_arch = "x86_64")]
-        {
-            CURRENT_TASK_PTR.write_current_raw(ptr as usize)
-        }
-        #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
-        {
-            let _guard = kernel_guard::IrqSave::new();
-            CURRENT_TASK_PTR.write_current_raw(ptr as usize)
-        }
-        #[cfg(target_arch = "aarch64")]
-        {
-            use tock_registers::interfaces::Writeable;
-            aarch64_cpu::registers::SP_EL0.set(ptr as u64)
-        }
+    #[cfg(target_arch = "x86_64")]
+    {
+        unsafe { CURRENT_TASK_PTR.write_current_raw(ptr as usize) }
+    }
+    #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
+    {
+        let _guard = kernel_guard::IrqSave::new();
+        unsafe { CURRENT_TASK_PTR.write_current_raw(ptr as usize) }
+    }
+    #[cfg(target_arch = "aarch64")]
+    {
+        use tock_registers::interfaces::Writeable;
+        aarch64_cpu::registers::SP_EL0.set(ptr as u64)
     }
 }
 
diff --git a/ulib/axlibc/src/strftime.rs b/ulib/axlibc/src/strftime.rs
index 59d6199811..ffdc8c5cdb 100644
--- a/ulib/axlibc/src/strftime.rs
+++ b/ulib/axlibc/src/strftime.rs
@@ -97,6 +97,14 @@ impl<T: Write> Write for CountingWriter<T> {
     }
 }
 
+#[inline]
+fn c_char_as_u8(c: c_char) -> u8 {
+    #[allow(clippy::unnecessary_cast)]
+    {
+        c as u8
+    }
+}
+
 unsafe fn strftime_inner<W: WriteByte>(
     w: W,
     format: *const c_char,
@@ -164,20 +172,20 @@ unsafe fn strftime_inner<W: WriteByte>(
         ];
 
         while *format != 0 {
-            if *format as u8 != b'%' {
-                w!(byte * format as u8);
+            if c_char_as_u8(*format) != b'%' {
+                w!(byte c_char_as_u8(*format));
                 format = format.offset(1);
                 continue;
             }
 
             format = format.offset(1);
 
-            if *format as u8 == b'E' || *format as u8 == b'O' {
+            if c_char_as_u8(*format) == b'E' || c_char_as_u8(*format) == b'O' {
                 // Ignore because these do nothing without locale
                 format = format.offset(1);
             }
 
-            match *format as u8 {
+            match c_char_as_u8(*format) {
                 b'%' => w!(byte b'%'),
                 b'n' => w!(byte b'\n'),
                 b't' => w!(byte b'\t'),
@@ -239,6 +247,7 @@ unsafe fn strftime_inner<W: WriteByte>(
 
 /// Convert date and time to a string.
 #[unsafe(no_mangle)]
+#[allow(clippy::unnecessary_cast)] // casting c_char to u8, c_char is either i8 or u8
 pub unsafe extern "C" fn strftime(
     buf: *mut c_char,
     size: ctypes::size_t,