Avoid usage of thread_local on DragonFlyBSD

Both __errno_location() and __error() return the same value, so the
__error() function can be implemented on the Rust side as
__errno_location(). This eliminates the sole use of thread_local in this
crate.

Author: bjorn3

build.rs

@@ -16,7 +16,6 @@ const ALLOWED_CFGS: &'static [&'static str] = &[
     "libc_const_extern_fn",
     "libc_const_extern_fn_unstable",
     "libc_deny_warnings",
-    "libc_thread_local",
 ];
 
 // Extra values to allow for check-cfg.
@@ -65,11 +64,6 @@ fn main() {
         set_cfg("libc_deny_warnings");
     }
 
-    // #[thread_local] is currently unstable
-    if rustc_dep_of_std {
-        set_cfg("libc_thread_local");
-    }
-
     // Rust >= 1.62.0 allows to use `const_extern_fn` for "Rust" and "C".
     if rustc_minor_ver >= 62 {
         set_cfg("libc_const_extern_fn");

libc-test/build.rs

@@ -67,12 +67,7 @@ fn do_ctest() {
 }
 
 fn ctest_cfg() -> ctest::TestGenerator {
-    let mut cfg = ctest::TestGenerator::new();
-    let libc_cfgs = ["libc_thread_local"];
-    for f in &libc_cfgs {
-        cfg.cfg(f, None);
-    }
-    cfg
+    ctest::TestGenerator::new()
 }
 
 fn do_semver() {

src/lib.rs

@@ -16,7 +16,6 @@
 #![cfg_attr(libc_deny_warnings, deny(warnings))]
 // Attributes needed when building as part of the standard library
 #![cfg_attr(feature = "rustc-dep-of-std", feature(link_cfg, no_core))]
-#![cfg_attr(libc_thread_local, feature(thread_local))]
 // Enable extra lints:
 #![cfg_attr(feature = "extra_traits", deny(missing_debug_implementations))]
 #![deny(missing_copy_implementations, safe_packed_borrows)]

src/unix/bsd/freebsdlike/dragonfly/errno.rs

@@ -1589,6 +1589,11 @@ f! {
     pub fn minor(dev: ::dev_t) -> ::c_int {
         (dev & 0xffff00ff) as ::c_int
     }
+
+    #[deprecated(since = "0.2.77", note = "Use `__errno_location()` instead")]
+    pub fn __error() -> *mut ::c_int {
+        super::__errno_location()
+    }
 }
 
 safe_f! {
@@ -1723,10 +1728,3 @@ extern "C" {
         entry: vm_map_entry_t,
     ) -> vm_map_entry_t;
 }
-
-cfg_if! {
-    if #[cfg(libc_thread_local)] {
-        mod errno;
-        pub use self::errno::*;
-    }
-}