comet-gc 0.1.3

Garbage collection library for implementing VMs in Rust
Documentation 
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/// Stack bounds for conservative stack marking. 
#[derive(Clone, Copy, PartialEq, Eq)]
pub struct StackBounds {
    pub origin: *mut u8,
    pub bound: *mut u8,
}

#[cfg(any(target_os = "macos", target_os = "ios"))]
impl StackBounds {
    pub unsafe fn new_thread_stack_bounds(thread: libc::pthread_t) -> Self {
        let origin = libc::pthread_get_stackaddr_np(thread);
        let size = libc::pthread_get_stacksize_np(thread);
        let bound = origin.add(size);
        Self {
            origin: origin.cast(),
            bound: bound.cast(),
        }
    }
    pub fn current_thread_stack_bounds() -> Self {
        unsafe { Self::new_thread_stack_bounds(thread_self() as _) }
    }
}

#[cfg(all(unix, not(any(target_os = "macos", target_os = "ios"))))]
impl StackBounds {
    #[cfg(target_os = "openbsd")]
    unsafe fn new_thread_stack_bounds(thread: libc::pthread_t) -> Self {
        let mut stack: libc::stack_t = core::mem::MaybeUninit::zeroed().assume_init();
        libc::pthread_stackseg_np(thread, &mut stack);
        let origin = stack.ss_sp;
        let bound = stack.origin.sub(stack.ss_size);
        return Self {
            origin: origin.cast(),
            bound: bound.cast(),
        };
    }

    #[cfg(not(target_os = "openbsd"))]
    unsafe fn new_thread_stack_bounds(thread: libc::pthread_t) -> Self {
        let mut bound = core::ptr::null_mut::<libc::c_void>();
        let mut stack_size = 0;
        let mut sattr: libc::pthread_attr_t = core::mem::MaybeUninit::zeroed().assume_init();
        libc::pthread_attr_init(&mut sattr);
        #[cfg(any(target_os = "freebsd", target_os = "netbsd"))]
        {
            libc::pthread_attr_get_np(thread, &mut sattr);
        }
        #[cfg(not(any(target_os = "freebsd", target_os = "netbsd")))]
        {
            libc::pthread_getattr_np(thread, &mut sattr);
        }
        let _rc = libc::pthread_attr_getstack(&sattr, &mut bound, &mut stack_size);
        libc::pthread_attr_destroy(&mut sattr);
        let origin = bound.add(stack_size);
        Self {
            bound: bound.cast(),
            origin: origin.cast(),
        }
    }

    pub fn current_thread_stack_bounds() -> Self {
        unsafe { Self::new_thread_stack_bounds(thread_self() as _) }
    }
}
#[allow(dead_code)]
pub(crate) fn thread_self() -> u64 {
    #[cfg(windows)]
    unsafe {
        extern "C" {
            fn GetCurrentThreadId() -> u32;
        }
        GetCurrentThreadId() as u64
    }
    #[cfg(unix)]
    unsafe {
        libc::pthread_self() as u64
    }
}
#[cfg(windows)]
impl StackBounds {
    pub unsafe fn current_thread_stack_bounds_internal() -> Self {
        use winapi::um::memoryapi::*;
        use winapi::um::winnt::*;
        let mut stack_origin: MEMORY_BASIC_INFORMATION =
            core::mem::MaybeUninit::zeroed().assume_init();
        VirtualQuery(
            &mut stack_origin as *mut MEMORY_BASIC_INFORMATION as *mut _,
            &mut stack_origin,
            core::mem::size_of::<MEMORY_BASIC_INFORMATION>(),
        );

        let origin = stack_origin
            .BaseAddress
            .cast::<u8>()
            .add(stack_origin.RegionSize as _);
        // The stack on Windows consists out of three parts (uncommitted memory, a guard page and present
        // committed memory). The 3 regions have different BaseAddresses but all have the same AllocationBase
        // since they are all from the same VirtualAlloc. The 3 regions are laid out in memory (from high to
        // low) as follows:
        //
        //    High |-------------------|  -----
        //         | committedMemory   |    ^
        //         |-------------------|    |
        //         | guardPage         | reserved memory for the stack
        //         |-------------------|    |
        //         | uncommittedMemory |    v
        //    Low  |-------------------|  ----- <--- stackOrigin.AllocationBase
        //
        // See http://msdn.microsoft.com/en-us/library/ms686774%28VS.85%29.aspx for more information.
        let mut uncommitted_memory: MEMORY_BASIC_INFORMATION =
            core::mem::MaybeUninit::zeroed().assume_init();
        VirtualQuery(
            stack_origin.AllocationBase as *mut _,
            &mut uncommitted_memory,
            core::mem::size_of::<MEMORY_BASIC_INFORMATION>(),
        );
        let mut guard_page: MEMORY_BASIC_INFORMATION =
            core::mem::MaybeUninit::zeroed().assume_init();
        VirtualQuery(
            uncommitted_memory
                .BaseAddress
                .cast::<u8>()
                .add(uncommitted_memory.RegionSize as _)
                .cast(),
            &mut guard_page,
            core::mem::size_of::<MEMORY_BASIC_INFORMATION>(),
        );
        let end_of_stack = stack_origin.AllocationBase as *mut u8;
        let bound = end_of_stack.add(guard_page.RegionSize as _);
        Self {
            origin: origin as *mut u8,
            bound,
        }
    }

    pub fn current_thread_stack_bounds() -> Self {
        unsafe { Self::current_thread_stack_bounds_internal() }
    }
}