added volatile type to prevent the compiler from optimizing writings to the buffer away

Cargo.toml

@@ -16,3 +16,4 @@ panic = "abort" # disable stack unwinding on panic
 
 [dependencies]
 bootloader = "0.9"
+volatile = "0.2.6"

src/vga_buffer.rs

@@ -1,3 +1,5 @@
+use volatile::Volatile;
+
 #[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 #[repr(u8)]
@@ -42,7 +44,15 @@ const BUFFER_WIDTH: usize = 80;
 
 #[repr(transparent)]
 struct Buffer {
-    chars: [[ScreenChar; BUFFER_WIDTH]; BUFFER_HEIGHT],
+    // wrapping the `ScreenChar` in a generic `Volatile`
+    // type prevents the compiler from optimizing writes
+    // away since the program only writes to it but never
+    // reads from it.
+    // by making it volatile we signal to the compiler
+    // that our write call have side-effects
+    // to interact with this type the `write()` and `read()`
+    // methods must be used now
+    chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],
 }
 
 pub struct Writer {
@@ -64,10 +74,10 @@ impl Writer {
                 let col = self.column_position;
 
                 let color_code = self.color_code;
-                self.buffer.chars[row][col] = ScreenChar {
+                self.buffer.chars[row][col].write(ScreenChar {
                     ascii_carachter: byte,
                     color_code,
-                };
+                });
                 self.column_position += 1;
             }
         }
@@ -89,10 +99,11 @@ impl Writer {
     }
 }
 
+// function to test things: to be removed
 pub fn print_something() {
     let mut writer = Writer {
         column_position: 0,
-        color_code: ColorCode::new(Color::Yellow, Color::Black),
+        color_code: ColorCode::new(Color::Pink, Color::Black),
         buffer: unsafe { &mut *(0xB8000 as *mut Buffer) },
     };