Fix atomic shim for macOS and fix warning

Author: bjorn3

config.sh

@@ -13,6 +13,12 @@ fi
 TARGET_TRIPLE=$(rustc -vV | grep host | cut -d: -f2 | tr -d " ")
 
 export RUSTFLAGS='-Cpanic=abort -Cdebuginfo=2 -Zpanic-abort-tests -Zcodegen-backend='$(pwd)'/target/'$CHANNEL'/librustc_codegen_cranelift.'$dylib_ext' --sysroot '$(pwd)'/build_sysroot/sysroot'
+
+# FIXME remove once the atomic shim is gone
+if [[ `uname` == 'Darwin' ]]; then
+   export RUSTFLAGS="$RUSTFLAGS -Clink-arg=-undefined -Clink-arg=dynamic_lookup"
+fi
+
 RUSTC="rustc $RUSTFLAGS -L crate=target/out --out-dir target/out"
 export RUSTC_LOG=warn # display metadata load errors
 

src/atomic_shim.rs

@@ -8,7 +8,7 @@ use crate::prelude::*;
 #[no_mangle]
 pub static mut __cg_clif_global_atomic_mutex: libc::pthread_mutex_t = libc::PTHREAD_MUTEX_INITIALIZER;
 
-pub fn init_global_lock(sess: &Session, module: &mut Module<impl Backend>, bcx: &mut FunctionBuilder<'_>) {
+pub fn init_global_lock(module: &mut Module<impl Backend>, bcx: &mut FunctionBuilder<'_>) {
     if std::env::var("SHOULD_RUN").is_ok () {
         // When using JIT, dylibs won't find the __cg_clif_global_atomic_mutex data object defined here,
         // so instead define it in the cg_clif dylib.

src/main_shim.rs

@@ -67,7 +67,7 @@ pub fn maybe_create_entry_wrapper(tcx: TyCtxt<'_>, module: &mut Module<impl Back
             let arg_argc = bcx.append_ebb_param(ebb, m.target_config().pointer_type());
             let arg_argv = bcx.append_ebb_param(ebb, m.target_config().pointer_type());
 
-            crate::atomic_shim::init_global_lock(tcx.sess, m, &mut bcx);
+            crate::atomic_shim::init_global_lock(m, &mut bcx);
 
             let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);