check for extern static size mismatches

[rust.git] / src / machine.rs

diff --git a/src/machine.rs b/src/machine.rs
index 1adfb83778116f7d383c5617afd6e84a9753db4f..67a6c997e99027e71a6e5d67d2d5acd22e7c8305 100644 (file)
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -638,12 +638,35 @@ fn extern_static_base_pointer(
     ) -> InterpResult<'tcx, Pointer<Provenance>> {
         let link_name = ecx.item_link_name(def_id);
         if let Some(&ptr) = ecx.machine.extern_statics.get(&link_name) {
+            // Various parts of the engine rely on `get_alloc_info` for size and alignment
+            // information. That uses the type information of this static.
+            // Make sure it matches the Miri allocation for this.
+            let Provenance::Concrete { alloc_id, .. } = ptr.provenance else {
+                panic!("extern_statics cannot contain wildcards")
+            };
+            let (shim_size, shim_align, _kind) = ecx.get_alloc_info(alloc_id);
+            let extern_decl_layout =
+                ecx.tcx.layout_of(ty::ParamEnv::empty().and(ecx.tcx.type_of(def_id))).unwrap();
+            if extern_decl_layout.size != shim_size || extern_decl_layout.align.abi != shim_align {
+                throw_unsup_format!(
+                    "`extern` static `{name}` from crate `{krate}` has been declared \
+                    with a size of {decl_size} bytes and alignment of {decl_align} bytes, \
+                    but Miri emulates it via an extern static shim \
+                    with a size of {shim_size} bytes and alignment of {shim_align} bytes",
+                    name = ecx.tcx.def_path_str(def_id),
+                    krate = ecx.tcx.crate_name(def_id.krate),
+                    decl_size = extern_decl_layout.size.bytes(),
+                    decl_align = extern_decl_layout.align.abi.bytes(),
+                    shim_size = shim_size.bytes(),
+                    shim_align = shim_align.bytes(),
+                )
+            }
             Ok(ptr)
         } else {
             throw_unsup_format!(
-                "`extern` static `{}` from crate `{}` is not supported by Miri",
-                ecx.tcx.def_path_str(def_id),
-                ecx.tcx.crate_name(def_id.krate),
+                "`extern` static `{name}` from crate `{krate}` is not supported by Miri",
+                name = ecx.tcx.def_path_str(def_id),
+                krate = ecx.tcx.crate_name(def_id.krate),
             )
         }
     }
@@ -754,15 +777,14 @@ fn expose_ptr(
         ptr: Pointer<Self::Provenance>,
     ) -> InterpResult<'tcx> {
         match ptr.provenance {
-            Provenance::Concrete { alloc_id, sb } => {
-                intptrcast::GlobalStateInner::expose_ptr(ecx, alloc_id, sb);
-            }
+            Provenance::Concrete { alloc_id, sb } =>
+                intptrcast::GlobalStateInner::expose_ptr(ecx, alloc_id, sb),
             Provenance::Wildcard => {
                 // No need to do anything for wildcard pointers as
                 // their provenances have already been previously exposed.
+                Ok(())
             }
         }
-        Ok(())
     }
 
     /// Convert a pointer with provenance into an allocation-offset pair,