fix: use pointer provenance APIs

Author: morrisonlevi

Cargo.lock

@@ -34,6 +34,7 @@ serde_json = {version = "1.0"}
 rand = { version = "0.8.5" }
 rand_distr = { version = "0.4.3" }
 rustc-hash = "1.1.0"
+sptr = "0.3"
 uuid = { version = "1.0", features = ["v4"] }
 
 [dev-dependencies]

profiling/Cargo.toml

@@ -92,9 +92,13 @@ unsafe fn extract_file_and_line(execute_data: &zend_execute_data) -> (Option<Thi
 
 #[cfg(php_run_time_cache)]
 mod detail {
+    // See: https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance
+    #![allow(unstable_name_collisions, unused_imports)]
+    use sptr::Strict;
+
     use super::*;
     use crate::string_set::StringSet;
-    use datadog_thin_str::{ThinHeader, ThinStr};
+    use datadog_thin_str::ThinStr;
     use log::{debug, trace};
     use std::cell::RefCell;
     use std::ops::Deref;
@@ -126,7 +130,7 @@ mod detail {
             // SAFETY: the slot is in-bounds from CacheSlot -> usize conv.
             let cached = unsafe { self.cache_slots.get_unchecked_mut(slot as usize) };
 
-            let ptr = *cached as *mut ThinHeader;
+            let ptr = sptr::from_exposed_addr_mut(*cached);
             match NonNull::new(ptr) {
                 Some(non_null) => {
                     // SAFETY: the string set is only reset between requests,
@@ -139,7 +143,7 @@ mod detail {
                     let string = f()?;
                     let thin_str = self.string_set.insert(&string);
                     let non_null = thin_str.header_ptr();
-                    *cached = non_null.as_ptr() as usize;
+                    *cached = non_null.as_ptr().expose_addr();
                     Some(string)
                 }
             }

profiling/src/profiling/stack_walking.rs

@@ -22,3 +22,4 @@ tagged-pointer = { version = "0.2", default-features = false }
 
 [dev-dependencies]
 naughty-strings = "0.2"
+sptr = { version = "0.3", default-features = false }

thin-str/Cargo.toml

@@ -265,6 +265,10 @@ mod ext {
 
 #[cfg(test)]
 mod tests {
+    // See: https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance
+    #![allow(unstable_name_collisions, unused_imports)]
+    use sptr::Strict;
+
     use super::*;
     use allocator_api2::alloc::Global;
 
@@ -327,15 +331,19 @@ This is a tribute.
     fn test_round_tripping_to_usize() {
         let datadog = "See inside any stack, any app, at any scale, anywhere.";
         let string = ThinString::from(datadog);
-
-        let bits = {
+        let ptr = {
             let thin_str = string.as_thin_str();
-            let non_null = thin_str.header_ptr();
-            non_null.as_ptr() as usize
+            thin_str.header_ptr().as_ptr()
         };
 
+        let bits = ptr.addr();
+
         let restored = {
-            let non_null = unsafe { ptr::NonNull::new_unchecked(bits as *mut ThinHeader) };
+            // with_addr allows us to restore the provenance of the pointer,
+            // and we can do this because we have the original to restore it.
+            // The actually PHP profiler will not have such things available,
+            // and should use `expose_addr` and similar.
+            let non_null = unsafe { ptr::NonNull::new_unchecked(ptr.with_addr(bits)) };
             unsafe { ThinStr::from_header(non_null) }
         };