fmt: {:p#} formats pointers padded to native width

Author: richo

src/libcore/fmt/mod.rs

@@ -844,12 +844,32 @@ 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 {
+        let old_width = f.width;
+        let old_flags = f.flags;
+
+        if f.flags & 1 << (FlagV1::Alternate as u32) > 0 {
+            f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
+
+            if let None = f.width {
+                f.width = POINTER_PADDING;
+            }
+        }
         f.flags |= 1 << (FlagV1::Alternate as u32);
+
         let ret = LowerHex::fmt(&(*self as usize), f);
-        f.flags &= !(1 << (FlagV1::Alternate as u32));
+
+        f.width = old_width;
+        f.flags = old_flags;
+
         ret
     }
 }

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

@@ -14,6 +14,11 @@ 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);
@@ -23,6 +28,8 @@ fn main() {
     let _ = format!("{:p}{:p}{:p}",
                     rc, arc, b);
 
+    assert_eq!(format!("{:#p}", p),
+               PTR.to_string());
     assert_eq!(format!("{:p}", p),
                "0x0");
 }

src/test/run-pass/ifmt.rs

@@ -42,6 +42,10 @@ impl fmt::Display for C {
 macro_rules! t {
     ($a:expr, $b:expr) => { assert_eq!($a, $b) }
 }
+#[cfg(target_pointer_width = "32")]
+const PTR: &'static str = "0x00001234";
+#[cfg(target_pointer_width = "64")]
+const PTR: &'static str = "0x0000000000001234";
 
 pub fn main() {
     // Various edge cases without formats
@@ -72,6 +76,8 @@ pub fn main() {
     t!(format!("{:X}", 10_usize), "A");
     t!(format!("{}", "foo"), "foo");
     t!(format!("{}", "foo".to_string()), "foo");
+    t!(format!("{:#p}", 0x1234 as *const isize), PTR);
+    t!(format!("{:#p}", 0x1234 as *mut isize), PTR);
     t!(format!("{:p}", 0x1234 as *const isize), "0x1234");
     t!(format!("{:p}", 0x1234 as *mut isize), "0x1234");
     t!(format!("{:x}", A), "aloha");