Print pointer addresses with %p.

src/format.rs

@@ -475,3 +475,21 @@ impl Printf for String {
         None
     }
 }
+
+impl<T> Printf for *const T {
+    fn format(&self, spec: &ConversionSpecifier) -> Result<String> {
+        (*self as usize).format(spec)
+    }
+    fn as_int(&self) -> Option<i32> {
+        None
+    }
+}
+
+impl<T> Printf for *mut T {
+    fn format(&self, spec: &ConversionSpecifier) -> Result<String> {
+        (*self as usize).format(spec)
+    }
+    fn as_int(&self) -> Option<i32> {
+        None
+    }
+}

tests/compare_to_libc.rs

@@ -3,6 +3,7 @@
 
 use std::convert::TryInto;
 use std::ffi::CString;
+use std::mem::size_of;
 use std::os::raw::c_char;
 
 use libc::snprintf;
@@ -113,3 +114,28 @@ fn test_str() {
     check_fmt_s("test %% with string: %s yay\n", "FOO");
     check_fmt("test char %c", '~');
 }
+
+#[test]
+fn test_ptr() {
+    let buf: [u8; 4] = [0; 4];
+    let ptr_const: *const u8 = buf.as_ptr();
+    let ptr_mut: *mut u8 = ptr_const.cast_mut();
+
+    // pointer: expects usize and pointer to have the same size
+    assert_eq!(size_of::<usize>(), size_of::<*const u8>(),);
+    check_fmt("%p", ptr_const);
+    check_fmt("%p", ptr_mut);
+
+    // numeric: works if you use the correct length specifier
+    if size_of::<usize>() == size_of::<u64>() {
+        check_fmt("%llx", ptr_const);
+        check_fmt("%llx", ptr_mut);
+        check_fmt("%#llx", ptr_const);
+        check_fmt("%#llx", ptr_mut);
+    } else if size_of::<usize>() == size_of::<u32>() {
+        check_fmt("%x", ptr_const);
+        check_fmt("%x", ptr_mut);
+        check_fmt("%#x", ptr_const);
+        check_fmt("%#x", ptr_mut);
+    }
+}