Merge recent updates from ch7.

user/src/bin/cat.rs

@@ -11,7 +11,6 @@ use user_lib::{
     close,
     read,
 };
-use alloc::string::String;
 
 #[no_mangle]
 pub fn main(argc: usize, argv: &[&str]) -> i32 {
@@ -22,13 +21,11 @@ pub fn main(argc: usize, argv: &[&str]) -> i32 {
     }
     let fd = fd as usize;
     let mut buf = [0u8; 16];
-    let mut s = String::new();
     loop {
         let size = read(fd, &mut buf) as usize;
         if size == 0 { break; }
-        s.push_str(core::str::from_utf8(&buf[..size]).unwrap());
+        println!("{}", core::str::from_utf8(&buf[..size]).unwrap());
     }
-    println!("{}", s);
     close(fd);
     0
-}
+}

user/src/bin/huge_write.rs

@@ -18,7 +18,7 @@ pub fn main() -> i32 {
     for i in 0..buffer.len() {
         buffer[i] = i as u8;
     }
-    let f = open("testf", OpenFlags::CREATE | OpenFlags::WRONLY);
+    let f = open("testf\0", OpenFlags::CREATE | OpenFlags::WRONLY);
     if f < 0 {
         panic!("Open test file failed!");
     }
@@ -33,4 +33,4 @@ pub fn main() -> i32 {
     let speed_kbs = size_mb * 1000000 / time_ms;
     println!("{}MiB written, time cost = {}ms, write speed = {}KiB/s", size_mb, time_ms, speed_kbs);
     0
-}
+}

user/src/bin/race_adder_arg.rs

@@ -29,6 +29,7 @@ unsafe fn f(count:usize) -> ! {
 
 #[no_mangle]
 pub fn main(argc: usize, argv: &[&str]) -> i32 {
+    let mut count = 0;
     if argc == 1 {
         count = THREAD_COUNT;
     } else if argc == 2 {