     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62

    #![cfg(target_thread_local)]
    #![unstable(feature = "thread_local_internals", issue = "0")]

    // Since what appears to be glibc 2.18 this symbol has been shipped which
    // GCC and clang both use to invoke destructors in thread_local globals, so
    // let's do the same!
    //
    // Note, however, that we run on lots older linuxes, as well as cross
    // compiling from a newer linux to an older linux, so we also have a
    // fallback implementation to use as well.
    //
    // Due to rust-lang/rust#18804, make sure this is not generic!
    #[cfg(any(target_os = "linux", target_os = "fuchsia", target_os = "hermit"))]
    pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
        use libc;
        use mem;
        use sys_common::thread_local::register_dtor_fallback;

        extern {
            #[linkage = "extern_weak"]
            static __dso_handle: *mut u8;
            #[linkage = "extern_weak"]
            static __cxa_thread_atexit_impl: *const libc::c_void;
        }
        if !__cxa_thread_atexit_impl.is_null() {
            type F = unsafe extern fn(dtor: unsafe extern fn(*mut u8),
                                      arg: *mut u8,
                                      dso_handle: *mut u8) -> libc::c_int;
            mem::transmute::<*const libc::c_void, F>(__cxa_thread_atexit_impl)
                (dtor, t, &__dso_handle as *const _ as *mut _);
            return
        }
        register_dtor_fallback(t, dtor);
    }

    // macOS's analog of the above linux function is this _tlv_atexit function.
    // The disassembly of thread_local globals in C++ (at least produced by
    // clang) will have this show up in the output.
    #[cfg(target_os = "macos")]
    pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
        extern {
            fn _tlv_atexit(dtor: unsafe extern fn(*mut u8),
                           arg: *mut u8);
        }
        _tlv_atexit(dtor, t);
    }

    pub fn requires_move_before_drop() -> bool {
        // The macOS implementation of TLS apparently had an odd aspect to it
        // where the pointer we have may be overwritten while this destructor
        // is running. Specifically if a TLS destructor re-accesses TLS it may
        // trigger a re-initialization of all TLS variables, paving over at
        // least some destroyed ones with initial values.
        //
        // This means that if we drop a TLS value in place on macOS that we could
        // revert the value to its original state halfway through the
        // destructor, which would be bad!
        //
        // Hence, we use `ptr::read` on macOS (to move to a "safe" location)
        // instead of drop_in_place.
        cfg!(target_os = "macos")
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)