support no_std on Windows

Author: RalfJung

src/tools/miri/ci.sh

@@ -75,7 +75,6 @@ function run_tests_minimal {
   ./miri test -- "$@"
 
   # Ensure that a small smoke test of cargo-miri works.
-  # Note: This doesn't work on windows because of TLS.
   cargo miri run --manifest-path test-cargo-miri/no-std-smoke/Cargo.toml
 }
 

src/tools/miri/src/shims/tls.rs

@@ -261,6 +261,11 @@ trait EvalContextPrivExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         // (that would be basically https://github.com/rust-lang/miri/issues/450),
         // we specifically look up the static in libstd that we know is placed
         // in that section.
+        if !this.have_module(&["std"]) {
+            // Looks like we are running in a `no_std` crate.
+            // That also means no TLS dtors callback to call.
+            return Ok(());
+        }
         let thread_callback =
             this.eval_windows("thread_local_key", "p_thread_callback")?.to_pointer(this)?;
         let thread_callback = this.get_ptr_fn(thread_callback)?.as_instance()?;

src/tools/miri/tests/pass/no_std.rs

@@ -1,9 +1,5 @@
 #![feature(lang_items, start)]
 #![no_std]
-// windows tls dtors go through libstd right now, thus this test
-// cannot pass. When windows tls dtors go through the special magic
-// windows linker section, we can run this test on windows again.
-//@ignore-target-windows: no-std not supported on Windows
 
 // Plumbing to let us use `writeln!` to host stdout: