buffer: switch to memmap2, destroy shm pools, never underflow refcounts

memmap 0.7 is unmaintained (RUSTSEC-2020-0077); memmap2 is a drop-in
replacement. Drop the unused shlex dependency.

Each resize created a new wl_shm_pool that was never destroyed; keep the
pool on the buffer and destroy it with it. A wl_buffer.release for a
buffer we didn't consider acquired used to underflow refcnt and wedge
rendering. Fix the lifetime-elision warnings while here.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Cargo.lock

@@ -462,16 +462,6 @@ version = "2.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "523dc4f511e55ab87b694dc30d0f820d60906ef06413f93d4d7a1385599cc149"
 
-[[package]]
-name = "memmap"
-version = "0.7.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6585fd95e7bb50d6cc31e20d4cf9afb4e2ba16c5846fc76793f11218da9c475b"
-dependencies = [
- "libc",
- "winapi",
-]
-
 [[package]]
 name = "memmap2"
 version = "0.9.5"
@@ -809,12 +799,6 @@ dependencies = [
  "digest",
 ]
 
-[[package]]
-name = "shlex"
-version = "1.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0fda2ff0d084019ba4d7c6f371c95d8fd75ce3524c3cb8fb653a3023f6323e64"
-
 [[package]]
 name = "simd-json"
 version = "0.13.8"
@@ -1289,13 +1273,12 @@ dependencies = [
  "fontconfig",
  "fuzzy-matcher",
  "libpulse-binding",
- "memmap",
+ "memmap2",
  "nix 0.26.4",
  "rcalc_lib",
  "rusttype",
  "serde",
  "serde_yaml",
- "shlex",
  "simd-json",
  "unicode-segmentation",
  "walkdir",

Cargo.toml

@@ -16,7 +16,7 @@ wayland-client = { version = "0.30", features = ["calloop", "log"] }
 wayland-protocols = { version = "0.30", features = ["client", "unstable", "staging"] }
 wayland-protocols-wlr = { version = "0.1", features = ["client"] }
 nix = "0.26" # 0.27 is breaking
-memmap = "0.7"
+memmap2 = "0.9"
 fontconfig = { version = "0.8.0", optional = true }
 rusttype = "0.9"
 # fontdue = "0.7"
@@ -27,7 +27,6 @@ walkdir = "2.4"
 
 unicode-segmentation = "1.10"
 fuzzy-matcher = "0.3"
-shlex = "1.3"
 
 xkbcommon = { version = "0.8", features = ["wayland"] }
 

src/buffer.rs

@@ -16,7 +16,7 @@ use nix::{
     unistd,
 };
 
-use memmap::MmapMut;
+use memmap2::MmapMut;
 
 use wayland_client::{
     protocol::{wl_buffer, wl_shm, wl_shm_pool},
@@ -78,11 +78,13 @@ fn create_shm_fd() -> io::Result<RawFd> {
 }
 
 pub struct ShmBuffer {
+    // Keeps the memfd alive for as long as the mapping and pool exist.
+    #[allow(dead_code)]
     pub file: File,
     pub mmap: MmapMut,
+    pub pool: wl_shm_pool::WlShmPool,
     pub buffer: wl_buffer::WlBuffer,
     pub refcnt: u32,
-    pub id: u32,
     pub last_damage: Vec<Geometry>,
 }
 
@@ -94,7 +96,6 @@ impl ShmBuffer {
         height: i32,
         stride: i32,
         format: wl_shm::Format,
-        id: u32,
     ) -> io::Result<ShmBuffer>
     where
         D: Dispatch<wl_shm_pool::WlShmPool, ()> + Dispatch<wl_buffer::WlBuffer, ()> + 'static,
@@ -103,15 +104,15 @@ impl ShmBuffer {
         let file = unsafe { File::from_raw_fd(mem_fd) };
         file.set_len((height * stride) as u64)?;
         let pool = shm.create_pool(mem_fd, height * stride, &qh, ());
-        let mmap = unsafe { MmapMut::map_mut(&file).unwrap() };
+        let mmap = unsafe { MmapMut::map_mut(&file)? };
         let buffer = pool.create_buffer(0, width, height, stride, format, &qh, ());
 
         Ok(ShmBuffer {
             refcnt: 0,
             file,
             mmap,
+            pool,
             buffer,
-            id,
             last_damage: Vec::new(),
         })
     }
@@ -121,26 +122,27 @@ impl ShmBuffer {
     }
 
     pub fn release(&mut self) {
-        self.refcnt -= 1;
+        // A compositor may release a buffer we never considered acquired
+        // (e.g. after a resize); never underflow and wedge the buffer.
+        self.refcnt = self.refcnt.saturating_sub(1);
     }
 }
 
 pub struct BufferManager {
     pub buffers: Vec<ShmBuffer>,
-    pub next_id: u32,
 }
 
 impl BufferManager {
     pub fn new() -> BufferManager {
         BufferManager {
             buffers: Vec::new(),
-            next_id: 0,
         }
     }
 
     pub fn clear_buffers(&mut self) {
         for buf in self.buffers.iter_mut() {
-            buf.buffer.destroy()
+            buf.buffer.destroy();
+            buf.pool.destroy();
         }
         self.buffers.clear()
     }
@@ -162,18 +164,15 @@ impl BufferManager {
     ) where
         D: Dispatch<wl_shm_pool::WlShmPool, ()> + Dispatch<wl_buffer::WlBuffer, ()> + 'static,
     {
-        let mut buf = ShmBuffer::new(
+        let buf = ShmBuffer::new(
             wl_shm,
             qh,
             dimensions.0,
             dimensions.1,
             dimensions.0 * 4,
             wl_shm::Format::Argb8888,
-            self.next_id,
         )
         .expect("unable to add buffer");
-        self.next_id += 1;
-        BufferView::new(&mut buf.mmap, (dimensions.0 as u32, dimensions.1 as u32));
         self.buffers.push(buf);
     }
 }
@@ -185,7 +184,7 @@ pub struct BufferView<'a> {
 }
 
 impl<'a> BufferView<'a> {
-    pub fn new(buf: &'a mut MmapMut, dimensions: (u32, u32)) -> BufferView {
+    pub fn new(buf: &'a mut MmapMut, dimensions: (u32, u32)) -> BufferView<'a> {
         let view = unsafe {
             std::slice::from_raw_parts_mut(
                 buf.as_mut_ptr() as *mut u32,
@@ -208,7 +207,7 @@ impl<'a> BufferView<'a> {
         }
     }
 
-    pub fn subdimensions(&mut self, subdimensions: (u32, u32, u32, u32)) -> BufferView {
+    pub fn subdimensions(&mut self, subdimensions: (u32, u32, u32, u32)) -> BufferView<'_> {
         let bounds = self.get_bounds();
         if cfg!(debug_assertions)
             && (subdimensions.0 + subdimensions.2 > bounds.2
@@ -232,11 +231,11 @@ impl<'a> BufferView<'a> {
         }
     }
 
-    pub fn subgeometry(&mut self, geo: Geometry) -> BufferView {
+    pub fn subgeometry(&mut self, geo: Geometry) -> BufferView<'_> {
         self.subdimensions((geo.x, geo.y, geo.width, geo.height))
     }
 
-    pub fn offset(&mut self, offset: (u32, u32)) -> BufferView {
+    pub fn offset(&mut self, offset: (u32, u32)) -> BufferView<'_> {
         let bounds = self.get_bounds();
         if cfg!(debug_assertions) && (offset.0 > bounds.2 || offset.1 > bounds.3) {
             panic!(