Merge pull request #4496 from RalfJung/ctor-ret-type

call_function helper: dont ICE on return type mismatches

Author: RalfJung

src/tools/miri/src/helpers.rs

@@ -437,7 +437,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     /// For now, arguments must be scalars (so that the caller does not have to know the layout).
     ///
     /// If you do not provide a return place, a dangling zero-sized place will be created
-    /// for your convenience.
+    /// for your convenience. This is only valid if the return type is `()`.
     fn call_function(
         &mut self,
         f: ty::Instance<'tcx>,
@@ -452,7 +452,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let mir = this.load_mir(f.def, None)?;
         let dest = match dest {
             Some(dest) => dest.clone(),
-            None => MPlaceTy::fake_alloc_zst(this.layout_of(mir.return_ty())?),
+            None => MPlaceTy::fake_alloc_zst(this.machine.layouts.unit),
         };
 
         // Construct a function pointer type representing the caller perspective.
@@ -465,6 +465,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         );
         let caller_fn_abi = this.fn_abi_of_fn_ptr(ty::Binder::dummy(sig), ty::List::empty())?;
 
+        // This will also show proper errors if there is any ABI mismatch.
         this.init_stack_frame(
             f,
             mir,

src/tools/miri/tests/fail/shims/ctor_wrong_ret_type.rs

@@ -0,0 +1,39 @@
+unsafe extern "C" fn ctor() -> i32 {
+    //~^ERROR: calling a function with return type i32 passing return place of type ()
+    0
+}
+
+#[rustfmt::skip]
+macro_rules! ctor {
+    ($ident:ident = $ctor:ident) => {
+        #[cfg_attr(
+            all(any(
+                target_os = "linux",
+                target_os = "android",
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "haiku",
+                target_os = "illumos",
+                target_os = "netbsd",
+                target_os = "openbsd",
+                target_os = "solaris",
+                target_os = "none",
+                target_family = "wasm",
+            )),
+            link_section = ".init_array"
+        )]
+        #[cfg_attr(windows, link_section = ".CRT$XCU")]
+        #[cfg_attr(
+            any(target_os = "macos", target_os = "ios"),
+            // We do not set the `mod_init_funcs` flag here since ctor/inventory also do not do
+            // that. See <https://github.com/rust-lang/miri/pull/4459#discussion_r2200115629>.
+            link_section = "__DATA,__mod_init_func"
+        )]
+        #[used]
+        static $ident: unsafe extern "C" fn() -> i32 = $ctor;
+    };
+}
+
+ctor! { CTOR = ctor }
+
+fn main() {}

src/tools/miri/tests/fail/shims/ctor_wrong_ret_type.stderr

@@ -0,0 +1,12 @@
+error: Undefined Behavior: calling a function with return type i32 passing return place of type ()
+   |
+   = note: Undefined Behavior occurred here
+   = note: (no span available)
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
+   = help: if you think this code should be accepted anyway, please report an issue with Miri
+   = note: BACKTRACE:
+
+error: aborting due to 1 previous error
+