Merge pull request #80 from ZettaScaleLabs/wasm-alloc

v6.4.1-rc1 (api=1.2.0, abi=1.0.0)

CHANGELOG.md

@@ -1,3 +1,10 @@
+# 6.4.1-rc1 (api=1.2.0, abi=1.0.0)
+- Found out that `libc` doesn't expose any allocation primitives for `wasm` targets.
+	- These targets now have a poor man's allocator. Be warned that while ABI-stable, this allocator is trivial and probably bad.  
+	  If `wasm` is indeed a target which you care a lot about, and you use stabby's allocation primitives a lot, you should probably roll out a better one (maybe even contribute it back).
+	- This allocator is not included in `stabby`'s cross-version contract: it may be swapped out for a better one in a patch-level API-bump.  
+	  If you need me _not_ to do so (i.e. you pass stabby's allocation primitives in `wasm` between multiple packages and can't pin your version of `stabby` down to patch for X reason), please reach out to me.
+
 # 6.2.1 (api=1.1.0, abi=1.0.0)
 - Add support for `#[stabby::stabby(version=10, module="my::module")]` to let you change the values in those fields without having to implement the whole trait yourself.
 - Add support for `serde` through the `serde` feature flag.

Cargo.toml

@@ -33,12 +33,12 @@ license = " EPL-2.0 OR Apache-2.0"
 categories = ["development-tools::ffi", "no-std::no-alloc"]
 repository = "https://github.com/ZettaScaleLabs/stabby"
 readme = "stabby/README.md"
-version = "6.2.1"                                           # Track
+version = "6.4.1-rc1"                                           # Track
 
 [workspace.dependencies]
-stabby-macros = { path = "./stabby-macros/", version = "6.2.1", default-features = false } # Track
-stabby-abi = { path = "./stabby-abi/", version = "6.2.1", default-features = false }       # Track
-stabby = { path = "./stabby/", version = "6.2.1", default-features = false }               # Track
+stabby-macros = { path = "./stabby-macros/", version = "6.4.1-rc1", default-features = false } # Track
+stabby-abi = { path = "./stabby-abi/", version = "6.4.1-rc1", default-features = false }       # Track
+stabby = { path = "./stabby/", version = "6.4.1-rc1", default-features = false }               # Track
 
 abi_stable = "0.11.2"
 criterion = "0.5.1"

release.py

@@ -10,7 +10,8 @@ def factor(x, base):
     return n
 
 def factor_version(version, base):
-    return ".".join([str(factor(int(x), base)) for x in version.split(".")])
+    v = re.sub(r'([0-9\.]+).*', "\\g<1>", version)
+    return ".".join([str(factor(int(x), base)) for x in v.split(".")])
 
 if __name__ == "__main__":
     if len(sys.argv) > 1 and sys.argv[1] == "publish":
@@ -27,13 +28,13 @@ def factor_version(version, base):
         with open(changelog) as clog:
             changelog_text = clog.read()
             for line in changelog_text.splitlines():
-                versions = re.findall(r"^#\s+([\d\.]+)", line)
+                versions = re.findall(r"^#\s+([\.\w\-]+)", line)
                 version = versions[0] if len(versions) else None
                 if version is not None:
                     break
         header = f"# {version} (api={factor_version(version, 2)}, abi={factor_version(version, 3)})"
         print(header)
-        changelog_text = re.sub(r"^#\s+([\d\.]+)\s*(\(api[^\)]+\))?", header, changelog_text)
+        changelog_text = re.sub(r"^#\s+([\.\w\-]+)(\s*\(api[^\)]+\))?", header, changelog_text)
         with open(changelog, "w") as clog:
             clog.write(changelog_text)
 

stabby-abi/src/alloc/libc_alloc.rs

@@ -14,7 +14,7 @@
 
 use super::Layout;
 
-#[cfg(not(windows))]
+#[cfg(not(any(windows, target_arch = "wasm32")))]
 use libc::posix_memalign;
 #[cfg(windows)]
 unsafe fn posix_memalign(this: &mut *mut core::ffi::c_void, size: usize, align: usize) -> i32 {
@@ -27,8 +27,12 @@ unsafe fn posix_memalign(this: &mut *mut core::ffi::c_void, size: usize, align:
 }
 #[cfg(windows)]
 use libc::aligned_free;
-#[cfg(not(windows))]
+#[cfg(not(any(windows, target_arch = "wasm32")))]
 use libc::free as aligned_free;
+#[cfg(not(target_arch = "wasm32"))]
+use libc::realloc;
+#[cfg(target_arch = "wasm32")]
+use wasm32_alloc::{free as aligned_free, posix_memalign, realloc};
 
 /// An allocator based on `libc::posix_memalign` or `libc::aligned_malloc` depending on the platform.
 ///
@@ -64,8 +68,8 @@ impl super::IAlloc for LibcAlloc {
         if new_layout.size == 0 {
             return core::ptr::null_mut();
         }
-        let mut new_ptr = unsafe { libc::realloc(ptr.cast(), new_layout.size) };
-        if new_ptr as usize % new_layout.align != 0 {
+        let mut new_ptr = unsafe { realloc(ptr.cast(), new_layout.size) };
+        if new_ptr.is_null() || new_ptr as usize % new_layout.align != 0 {
             let mut ptr = core::ptr::null_mut();
             let err = unsafe { posix_memalign(&mut ptr, new_layout.align, new_layout.size) };
             if err == 0 {
@@ -83,3 +87,221 @@ impl super::IAlloc for LibcAlloc {
         new_ptr.cast()
     }
 }
+
+#[cfg(target_arch = "wasm32")]
+mod wasm32_alloc {
+    use core::{
+        ffi::c_void,
+        mem::MaybeUninit,
+        sync::atomic::{AtomicPtr, Ordering},
+    };
+
+    #[repr(C)]
+    struct Slot {
+        size: usize,
+        lower: Option<&'static mut Slot>,
+        padding: usize,
+        _reserved: usize,
+    }
+    impl core::cmp::Ord for Slot {
+        fn cmp(&self, other: &Self) -> core::cmp::Ordering {
+            (self as *const Self).cmp(&(other as *const Self))
+        }
+    }
+    impl core::cmp::PartialOrd for Slot {
+        fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
+            Some(self.cmp(other))
+        }
+    }
+    impl core::cmp::Eq for Slot {}
+    impl core::cmp::PartialEq for Slot {
+        fn eq(&self, other: &Self) -> bool {
+            core::ptr::eq(self, other)
+        }
+    }
+    impl Slot {
+        const fn full_size(&self) -> usize {
+            core::mem::size_of::<Self>() + self.size
+        }
+        const fn start(&self) -> *const u8 {
+            unsafe { (self as *const Self).cast::<u8>().sub(self.padding) }
+        }
+        const fn end(&self) -> *const u8 {
+            unsafe { (self as *const Self).cast::<u8>().add(self.full_size()) }
+        }
+        fn shift(&'static mut self, target_align: usize) -> &'static mut Self {
+            let required_padding = target_align - core::mem::size_of::<Self>();
+            let padding = self.padding;
+            if padding == required_padding {
+                return self;
+            }
+            self.size += padding;
+            self.padding = 0;
+            let new_addr = unsafe {
+                (self as *mut Self)
+                    .cast::<u8>()
+                    .offset(padding as isize - required_padding as isize)
+            };
+            unsafe {
+                core::ptr::copy(
+                    (self as *const Self).cast(),
+                    new_addr,
+                    core::mem::size_of::<Self>(),
+                );
+                &mut *new_addr.cast()
+            }
+        }
+        fn split(self: &mut &'static mut Self, at: usize) -> Option<&'static mut Self> {
+            let size = self.size;
+            (size > at + core::mem::size_of::<Self>()).then(move || {
+                self.size = at;
+                let slot = unsafe { &mut *(self.end() as *mut MaybeUninit<Slot>) };
+                slot.write(Slot {
+                    size: size - at + core::mem::size_of::<Self>(),
+                    lower: None,
+                    padding: 0,
+                    _reserved: 0,
+                })
+            })
+        }
+    }
+
+    const PAGESIZE: usize = 65536;
+    #[repr(C)]
+    struct Allocator {
+        free_list: AtomicPtr<Slot>,
+    }
+    struct Slots {
+        list: Option<&'static mut Slot>,
+    }
+    impl Drop for Slots {
+        fn drop(&mut self) {
+            ALLOC.free_list.store(
+                unsafe {
+                    core::mem::transmute::<Option<&'static mut Slot>, *mut Slot>(self.list.take())
+                },
+                Ordering::Release,
+            );
+        }
+    }
+    impl Slots {
+        fn insert(&mut self, mut slot: &'static mut Slot) {
+            slot = slot.shift(core::mem::size_of::<Slot>());
+            let mut head = &mut self.list;
+            while let Some(h) = head {
+                if *h < slot {
+                    if core::ptr::eq(h.end(), slot.start()) {
+                        h.size += slot.full_size();
+                        return;
+                    }
+                    break;
+                }
+                head = unsafe {
+                    core::mem::transmute::<
+                        &mut Option<&'static mut Slot>,
+                        &mut Option<&'static mut Slot>,
+                    >(&mut h.lower)
+                };
+            }
+            slot.lower = head.take();
+            *head = Some(slot)
+        }
+        fn take(&mut self, size: usize, align: usize) -> Option<&'static mut Slot> {
+            let req = size + align;
+            let slot_owner = self.select_slot(req)?;
+            let mut slot = slot_owner.take()?;
+            let lower = slot.lower.take();
+            *slot_owner = slot.split(size);
+            match slot_owner {
+                Some(owner) => owner.lower = lower,
+                None => *slot_owner = lower,
+            }
+            Some(slot)
+        }
+        fn select_slot(&mut self, size: usize) -> Option<&mut Option<&'static mut Slot>> {
+            let mut head = unsafe {
+                core::mem::transmute::<&mut Option<&'static mut Slot>, &mut Option<&'static mut Slot>>(
+                    &mut self.list,
+                )
+            };
+            while let Some(h) = head {
+                if h.size < size {
+                    head = unsafe {
+                        core::mem::transmute::<
+                            &mut Option<&'static mut Slot>,
+                            &mut Option<&'static mut Slot>,
+                        >(&mut h.lower)
+                    };
+                } else {
+                    return Some(head);
+                }
+            }
+            self.grow_take(size)
+        }
+        fn grow_take(&mut self, size: usize) -> Option<&mut Option<&'static mut Slot>> {
+            let added_pages = (size / PAGESIZE) + 2;
+            let start = core::arch::wasm32::memory_grow(0, added_pages);
+            if start == usize::MAX {
+                return None;
+            }
+            let slot = unsafe { &mut *((start * PAGESIZE) as *mut MaybeUninit<Slot>) };
+            let slot = slot.write(Slot {
+                size: added_pages * PAGESIZE - core::mem::size_of::<Slot>(),
+                lower: None,
+                padding: 0,
+                _reserved: 0,
+            });
+            self.insert(slot);
+            Some(&mut self.list)
+        }
+    }
+    impl Allocator {
+        const fn new() -> Self {
+            Self {
+                free_list: AtomicPtr::new(core::ptr::null_mut()),
+            }
+        }
+        fn lock(&self) -> Slots {
+            loop {
+                let list = self
+                    .free_list
+                    .swap(usize::MAX as *mut Slot, Ordering::AcqRel);
+                if list as usize != usize::MAX {
+                    return Slots {
+                        list: unsafe { list.as_mut() },
+                    };
+                }
+                core::hint::spin_loop();
+            }
+        }
+    }
+    static ALLOC: Allocator = Allocator::new();
+    pub unsafe fn posix_memalign(
+        this: &mut *mut core::ffi::c_void,
+        mut size: usize,
+        mut align: usize,
+    ) -> i32 {
+        size = size.max(64);
+        align = align.max(8);
+        match ALLOC.lock().take(size, align) {
+            Some(slot) => {
+                *this = (slot as *mut Slot).add(1).cast();
+                0
+            }
+            None => -1,
+        }
+    }
+    pub unsafe fn realloc(p: *mut c_void, new_size: usize) -> *mut c_void {
+        let mut this = core::ptr::null_mut();
+        if posix_memalign(&mut this, new_size, 8) != 0 {
+            return core::ptr::null_mut();
+        }
+        let slot = p.cast::<Slot>().sub(1);
+        unsafe { core::ptr::copy_nonoverlapping(p.cast::<u8>(), this.cast(), (*slot).size) };
+        this
+    }
+    pub unsafe fn free(p: *mut c_void) {
+        let slot = p.cast::<Slot>().sub(1);
+        ALLOC.lock().insert(&mut *slot);
+    }
+}