From 40a0ecc65f89d6d34c910996168a3a0e6d5bdadb Mon Sep 17 00:00:00 2001
From: Nika Layzell <nika@thelayzells.com>
Date: Wed, 19 May 2021 17:29:23 +0000
Subject: [PATCH] Bug 1709935 - Support XPCOM refcount logging with rust-xpcom,
 r=xpcom-reviewers,mccr8

Differential Revision: https://phabricator.services.mozilla.com/D115086
---
 toolkit/library/rust/shared/Cargo.toml   |  2 +-
 xpcom/rust/xpcom/Cargo.toml              |  1 +
 xpcom/rust/xpcom/src/refptr.rs           | 54 ++++++++++++++++++++++++
 xpcom/rust/xpcom/xpcom_macros/src/lib.rs | 31 +++++++++++++-
 4 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/toolkit/library/rust/shared/Cargo.toml b/toolkit/library/rust/shared/Cargo.toml
index 8b8486f77294..88fcb30cb8e8 100644
--- a/toolkit/library/rust/shared/Cargo.toml
+++ b/toolkit/library/rust/shared/Cargo.toml
@@ -85,7 +85,7 @@ cubeb-remoting = ["cubeb-sys", "audioipc-client", "audioipc-server"]
 cubeb_coreaudio_rust = ["cubeb-sys", "cubeb-coreaudio"]
 cubeb_pulse_rust = ["cubeb-sys", "cubeb-pulse"]
 gecko_debug = ["geckoservo/gecko_debug", "nsstring/gecko_debug"]
-gecko_refcount_logging = ["geckoservo/gecko_refcount_logging"]
+gecko_refcount_logging = ["geckoservo/gecko_refcount_logging", "xpcom/gecko_refcount_logging"]
 simd-accel = ["encoding_glue/simd-accel", "jsrust_shared/simd-accel"]
 moz_memory = []
 moz_places = ["bookmark_sync"]
diff --git a/xpcom/rust/xpcom/Cargo.toml b/xpcom/rust/xpcom/Cargo.toml
index 8de17167b089..0c4566fefa68 100644
--- a/xpcom/rust/xpcom/Cargo.toml
+++ b/xpcom/rust/xpcom/Cargo.toml
@@ -15,3 +15,4 @@ thin-vec = { version = "0.2.1", features = ["gecko-ffi"] }
 
 [features]
 thread_sanitizer = []
+gecko_refcount_logging = []
diff --git a/xpcom/rust/xpcom/src/refptr.rs b/xpcom/rust/xpcom/src/refptr.rs
index 52bbe0821648..55ce0c6dc583 100644
--- a/xpcom/rust/xpcom/src/refptr.rs
+++ b/xpcom/rust/xpcom/src/refptr.rs
@@ -319,3 +319,57 @@ impl AtomicRefcnt {
         self.0.load(Ordering::Acquire) as nsrefcnt
     }
 }
+
+#[cfg(feature = "gecko_refcount_logging")]
+pub mod trace_refcnt {
+    use crate::interfaces::nsrefcnt;
+
+    extern "C" {
+        pub fn NS_LogCtor(aPtr: *mut libc::c_void, aTypeName: *const libc::c_char, aSize: u32);
+        pub fn NS_LogDtor(aPtr: *mut libc::c_void, aTypeName: *const libc::c_char, aSize: u32);
+        pub fn NS_LogAddRef(
+            aPtr: *mut libc::c_void,
+            aRefcnt: nsrefcnt,
+            aClass: *const libc::c_char,
+            aClassSize: u32,
+        );
+        pub fn NS_LogRelease(
+            aPtr: *mut libc::c_void,
+            aRefcnt: nsrefcnt,
+            aClass: *const libc::c_char,
+            aClassSize: u32,
+        );
+    }
+}
+
+// stub inline methods for the refcount logging functions for when the feature
+// is disabled.
+#[cfg(not(feature = "gecko_refcount_logging"))]
+pub mod trace_refcnt {
+    use crate::interfaces::nsrefcnt;
+
+    #[inline]
+    #[allow(non_snake_case)]
+    pub unsafe extern "C" fn NS_LogCtor(_: *mut libc::c_void, _: *const libc::c_char, _: u32) {}
+    #[inline]
+    #[allow(non_snake_case)]
+    pub unsafe extern "C" fn NS_LogDtor(_: *mut libc::c_void, _: *const libc::c_char, _: u32) {}
+    #[inline]
+    #[allow(non_snake_case)]
+    pub unsafe extern "C" fn NS_LogAddRef(
+        _: *mut libc::c_void,
+        _: nsrefcnt,
+        _: *const libc::c_char,
+        _: u32,
+    ) {
+    }
+    #[inline]
+    #[allow(non_snake_case)]
+    pub unsafe extern "C" fn NS_LogRelease(
+        _: *mut libc::c_void,
+        _: nsrefcnt,
+        _: *const libc::c_char,
+        _: u32,
+    ) {
+    }
+}
diff --git a/xpcom/rust/xpcom/xpcom_macros/src/lib.rs b/xpcom/rust/xpcom/xpcom_macros/src/lib.rs
index aa5b76a18f94..e535d96e90ae 100644
--- a/xpcom/rust/xpcom/xpcom_macros/src/lib.rs
+++ b/xpcom/rust/xpcom/xpcom_macros/src/lib.rs
@@ -658,7 +658,23 @@ fn xpcom(init: DeriveInput) -> Result<TokenStream, syn::Error> {
         coerce_impl.push(coerce);
     }
 
+    let size_for_logs = if real.generics.params.is_empty() {
+        quote!(::std::mem::size_of::<Self>() as u32)
+    } else {
+        // Refcount logging requires all types with the same name to have the
+        // same size, and generics aren't taken into account when creating our
+        // name string, so we need to make sure that all possible instantiations
+        // report the same size. To do that, we fake a size based on the number
+        // of vtable pointers and the known refcount field.
+        let fake_size_npointers = bases.len() + 1;
+        quote!((::std::mem::size_of::<usize>() * #fake_size_npointers) as u32)
+    };
+
     let (impl_generics, ty_generics, where_clause) = real.generics.split_for_impl();
+    let name_for_logs = quote!(
+        concat!(module_path!(), "::", stringify!(#name #ty_generics), "\0").as_ptr()
+            as *const ::xpcom::reexports::libc::c_char
+    );
     Ok(quote! {
         #real
 
@@ -695,12 +711,25 @@ fn xpcom(init: DeriveInput) -> Result<TokenStream, syn::Error> {
 
             /// Automatically generated implementation of AddRef for nsISupports.
             #vis unsafe fn AddRef(&self) -> ::xpcom::interfaces::nsrefcnt {
-                self.__refcnt.inc()
+                let new = self.__refcnt.inc();
+                ::xpcom::trace_refcnt::NS_LogAddRef(
+                    self as *const _ as *mut ::xpcom::reexports::libc::c_void,
+                    new,
+                    #name_for_logs,
+                    #size_for_logs,
+                );
+                new
             }
 
             /// Automatically generated implementation of Release for nsISupports.
             #vis unsafe fn Release(&self) -> ::xpcom::interfaces::nsrefcnt {
                 let new = self.__refcnt.dec();
+                ::xpcom::trace_refcnt::NS_LogRelease(
+                    self as *const _ as *mut ::xpcom::reexports::libc::c_void,
+                    new,
+                    #name_for_logs,
+                    #size_for_logs,
+                );
                 if new == 0 {
                     // dealloc
                     ::std::boxed::Box::from_raw(self as *const Self as *mut Self);