From 333eb85d4b7dc51ada5202c35d5c67663111f403 Mon Sep 17 00:00:00 2001
From: Richo Healey <richo@psych0tik.net>
Date: Tue, 7 Apr 2015 17:53:55 -0700
Subject: [PATCH] fmt: {:p#} formats pointers padded to native width

---
 src/libcore/fmt/mod.rs                 | 26 +++++++++++++++++++++++++-
 src/test/run-pass/fmt-pointer-trait.rs |  8 ++++++++
 src/test/run-pass/ifmt.rs              |  8 ++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index be804327663e5..2a7569e3b731d 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -847,9 +847,33 @@ impl Display for char {
 #[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;
+
+        // The alternate flag is already treated by LowerHex as being special-
+        // it denotes whether to prefix with 0x. We use it to work out whether
+        // or not to zero extend, and then unconditionally set it to get the
+        // prefix.
+        if f.flags & 1 << (FlagV1::Alternate as u32) > 0 {
+            f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
+
+            if let None = f.width {
+                // The formats need two extra bytes, for the 0x
+                if cfg!(target_pointer_width = "32") {
+                    f.width = Some(10);
+                }
+                if cfg!(target_pointer_width = "64") {
+                    f.width = Some(18);
+                }
+            }
+        }
         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
     }
 }
diff --git a/src/test/run-pass/fmt-pointer-trait.rs b/src/test/run-pass/fmt-pointer-trait.rs
index be8ecde67836e..0f4b0bfcec983 100644
--- a/src/test/run-pass/fmt-pointer-trait.rs
+++ b/src/test/run-pass/fmt-pointer-trait.rs
@@ -23,6 +23,14 @@ fn main() {
     let _ = format!("{:p}{:p}{:p}",
                     rc, arc, b);
 
+    if cfg!(target_pointer_width = "32") {
+        assert_eq!(format!("{:#p}", p),
+                   "0x00000000");
+    }
+    if cfg!(target_pointer_width = "64") {
+        assert_eq!(format!("{:#p}", p),
+                   "0x0000000000000000");
+    }
     assert_eq!(format!("{:p}", p),
                "0x0");
 }
diff --git a/src/test/run-pass/ifmt.rs b/src/test/run-pass/ifmt.rs
index 41c859214e96b..7230fe71e21ee 100644
--- a/src/test/run-pass/ifmt.rs
+++ b/src/test/run-pass/ifmt.rs
@@ -72,6 +72,14 @@ pub fn main() {
     t!(format!("{:X}", 10_usize), "A");
     t!(format!("{}", "foo"), "foo");
     t!(format!("{}", "foo".to_string()), "foo");
+    if cfg!(target_pointer_width = "32") {
+        t!(format!("{:#p}", 0x1234 as *const isize), "0x00001234");
+        t!(format!("{:#p}", 0x1234 as *mut isize), "0x00001234");
+    }
+    if cfg!(target_pointer_width = "64") {
+        t!(format!("{:#p}", 0x1234 as *const isize), "0x0000000000001234");
+        t!(format!("{:#p}", 0x1234 as *mut isize), "0x0000000000001234");
+    }
     t!(format!("{:p}", 0x1234 as *const isize), "0x1234");
     t!(format!("{:p}", 0x1234 as *mut isize), "0x1234");
     t!(format!("{:x}", A), "aloha");