fmt: Pad pointers to native pointer width

Author: richo

src/libcore/fmt/mod.rs

@@ -844,12 +844,29 @@ impl Display for char {
     }
 }
 
+// Two extra bytes for 0x
+#[cfg(target_pointer_width = "32")]
+const POINTER_PADDING: Option<usize> = Some(10);
+#[cfg(target_pointer_width = "64")]
+const POINTER_PADDING: Option<usize> = Some(18);
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Pointer for *const T {
     fn fmt(&self, f: &mut Formatter) -> Result {
         f.flags |= 1 << (FlagV1::Alternate as u32);
+        f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
+
+        let old_width = f.width;
+        if let None = f.width {
+            f.width = POINTER_PADDING;
+        }
+
         let ret = LowerHex::fmt(&(*self as usize), f);
+
+        f.width = old_width;
         f.flags &= !(1 << (FlagV1::Alternate as u32));
+        f.flags &= !(1 << (FlagV1::SignAwareZeroPad as u32));
+
         ret
     }
 }

src/test/run-pass/fmt-pointer-trait.rs

@@ -4,6 +4,11 @@ use std::ptr;
 use std::rc::Rc;
 use std::sync::Arc;
 
+#[cfg(target_pointer_width = "32")]
+const PTR: &'static str = "0x00000000";
+#[cfg(target_pointer_width = "64")]
+const PTR: &'static str = "0x0000000000000000";
+
 fn main() {
     let p: *const libc::c_void = ptr::null();
     let rc = Rc::new(1usize);
@@ -14,5 +19,5 @@ fn main() {
                     rc, arc, b);
 
     assert_eq!(format!("{:p}", p),
-               "0x0");
+               PTR.to_string());
 }