From c45e485bcafd05509de3c03b6e92c749b527c5f9 Mon Sep 17 00:00:00 2001
From: Jubilee Young <workingjubilee@gmail.com>
Date: Mon, 5 Feb 2024 13:19:41 -0800
Subject: [PATCH] Add is_non_null to pointers

---
 pgrx/src/lib.rs              |  1 +
 pgrx/src/list/flat_list.rs   |  9 +++++----
 pgrx/src/list/linked_list.rs |  7 ++++---
 pgrx/src/ptr.rs              | 15 +++++++++++++++
 4 files changed, 25 insertions(+), 7 deletions(-)
 create mode 100644 pgrx/src/ptr.rs

diff --git a/pgrx/src/lib.rs b/pgrx/src/lib.rs
index 6f74fd548d..6c3c78e3ae 100644
--- a/pgrx/src/lib.rs
+++ b/pgrx/src/lib.rs
@@ -88,6 +88,7 @@ pub use once_cell;
 
 /// Not ready for public exposure.
 mod layout;
+mod ptr;
 mod slice;
 mod toast;
 
diff --git a/pgrx/src/list/flat_list.rs b/pgrx/src/list/flat_list.rs
index 59c135172a..c414dc60f1 100644
--- a/pgrx/src/list/flat_list.rs
+++ b/pgrx/src/list/flat_list.rs
@@ -1,6 +1,7 @@
 use super::{Enlist, List, ListCell, ListHead};
 use crate::memcx::MemCx;
 use crate::pg_sys;
+use crate::ptr::PointerExt;
 use crate::seal::Sealed;
 use core::cmp;
 use core::ffi;
@@ -195,7 +196,7 @@ impl<'cx, T: Enlist> List<'cx, T> {
         };
 
         // Remember to check that our raw ptr is non-null
-        if raw != ptr::null_mut() {
+        if raw.is_non_null() {
             // Shorten the list to prohibit interaction with List's state after drain_start.
             // Note this breaks List repr invariants in the `drain_start == 0` case, but
             // we only consider returning the list ptr to `&mut self` if Drop is completed
@@ -332,11 +333,11 @@ unsafe fn grow_list(list: &mut pg_sys::List, target: usize) {
     if list.elements == ptr::addr_of_mut!(list.initial_elements).cast() {
         // first realloc, we can't dealloc the elements ptr, as it isn't its own alloc
         let context = pg_sys::GetMemoryChunkContext(list as *mut pg_sys::List as *mut _);
-        if context == ptr::null_mut() {
+        if context.is_null() {
             panic!("Context free list?");
         }
         let buf = pg_sys::MemoryContextAlloc(context, alloc_size);
-        if buf == ptr::null_mut() {
+        if buf.is_null() {
             panic!("List allocation failure");
         }
         ptr::copy_nonoverlapping(list.elements, buf.cast(), list.length as _);
@@ -382,7 +383,7 @@ pub struct Drain<'a, 'cx, T> {
 
 impl<'a, 'cx, T> Drop for Drain<'a, 'cx, T> {
     fn drop(&mut self) {
-        if self.raw == ptr::null_mut() {
+        if self.raw.is_null() {
             return;
         }
 
diff --git a/pgrx/src/list/linked_list.rs b/pgrx/src/list/linked_list.rs
index 820bda2354..07fa49ae9e 100644
--- a/pgrx/src/list/linked_list.rs
+++ b/pgrx/src/list/linked_list.rs
@@ -1,6 +1,7 @@
 use super::{Enlist, List, ListCell, ListHead};
 use crate::memcx::MemCx;
 use crate::pg_sys;
+use crate::ptr::PointerExt;
 use crate::seal::Sealed;
 use core::cmp;
 use core::ffi;
@@ -209,7 +210,7 @@ impl<'cx, T: Enlist> List<'cx, T> {
         };
 
         // Remember to check that our raw ptr is non-null
-        if raw != ptr::null_mut() {
+        if raw.is_non_null() {
             // Shorten the list to prohibit interaction with List's state after drain_start.
             // Note this breaks List repr invariants in the `drain_start == 0` case, but
             // we only consider returning the list ptr to `&mut self` if Drop is completed
@@ -328,7 +329,7 @@ unsafe fn cons_cell<T: Enlist>(list: &mut pg_sys::List, value: T) -> *mut pg_sys
 
 unsafe fn destroy_list(list: *mut pg_sys::List) {
     let mut cell = (*list).head;
-    while cell != ptr::null_mut() {
+    while cell.is_non_null() {
         let next = (*cell).next;
         pg_sys::pfree(cell.cast());
         cell = next;
@@ -496,7 +497,7 @@ impl<T: Enlist> Iterator for RawCellIter<T> {
 
     #[inline]
     fn next(&mut self) -> Option<T> {
-        if self.ptr != ptr::null_mut() {
+        if self.ptr.is_non_null() {
             let ptr = self.ptr;
             // SAFETY: It's assumed that the pointers are valid on construction
             unsafe {
diff --git a/pgrx/src/ptr.rs b/pgrx/src/ptr.rs
new file mode 100644
index 0000000000..50a24b0936
--- /dev/null
+++ b/pgrx/src/ptr.rs
@@ -0,0 +1,15 @@
+pub(crate) trait PointerExt {
+    fn is_non_null(&self) -> bool;
+}
+
+impl<T> PointerExt for *mut T {
+    fn is_non_null(&self) -> bool {
+        !self.is_null()
+    }
+}
+
+impl<T> PointerExt for *const T {
+    fn is_non_null(&self) -> bool {
+        !self.is_null()
+    }
+}