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//! Destructor registration for Linux-like systems.
//!
//! Since what appears to be version 2.18, glibc has shipped the
//! `__cxa_thread_atexit_impl` symbol which GCC and clang both use to invoke
//! destructors in C++ thread_local globals. This function does exactly what
//! we want: it schedules a callback which will be run at thread exit with the
//! provided argument.
//!
//! Unfortunately, our minimum supported glibc version (at the time of writing)
//! is 2.17, so we can only link this symbol weakly and need to use the
//! [`list`](super::list) destructor implementation as fallback.
use crate::mem::transmute;
pub unsafe fn register(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
/// This is necessary because the __cxa_thread_atexit_impl implementation
/// std links to by default may be a C or C++ implementation that was not
/// compiled using the Clang integer normalization option.
#[cfg(sanitizer_cfi_normalize_integers)]
use core::ffi::c_int;
#[cfg(not(sanitizer_cfi_normalize_integers))]
#[cfi_encoding = "i"]
#[repr(transparent)]
#[allow(non_camel_case_types)]
pub struct c_int(#[allow(dead_code)] pub core::ffi::c_int);
unsafe extern "C" {
#[linkage = "extern_weak"]
static __dso_handle: *mut u8;
#[linkage = "extern_weak"]
static __cxa_thread_atexit_impl: Option<
extern "C" fn(
unsafe extern "C" fn(*mut libc::c_void),
*mut libc::c_void,
*mut libc::c_void,
) -> c_int,
>;
}
if let Some(f) = unsafe { __cxa_thread_atexit_impl } {
unsafe {
f(
transmute::<unsafe extern "C" fn(*mut u8), unsafe extern "C" fn(*mut libc::c_void)>(
dtor,
),
t.cast(),
(&raw const __dso_handle) as *mut _,
);
}
} else {
unsafe {
super::list::register(t, dtor);
}
}
}
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