mark extern block function signatures as FIXED (#966)

Fixes #965. The inputs and outputs of body-owners are already marked as
fixed, but the traversal of `all_fn_dids` does not include function
declarations in `extern` blocks

Author: aneksteind

c2rust-analyze/src/context.rs

@@ -277,6 +277,7 @@ pub struct GlobalAnalysisCtxt<'tcx> {
     pub fn_callers: HashMap<DefId, Vec<DefId>>,
 
     pub fn_sigs: HashMap<DefId, LFnSig<'tcx>>,
+
     /// `DefId`s of functions where analysis failed, and a [`PanicDetail`] explaining the reason
     /// for each failure.
     pub fns_failed: HashMap<DefId, PanicDetail>,

c2rust-analyze/src/main.rs

@@ -321,6 +321,55 @@ where
     }
 }
 
+fn gather_foreign_sigs<'tcx>(gacx: &mut GlobalAnalysisCtxt<'tcx>, tcx: TyCtxt<'tcx>) {
+    for did in tcx
+        .hir_crate_items(())
+        .foreign_items()
+        .map(|item| item.def_id.to_def_id())
+        .filter(|did| matches!(tcx.def_kind(did), DefKind::Fn | DefKind::AssocFn))
+    {
+        let sig = tcx.erase_late_bound_regions(tcx.fn_sig(did));
+        let inputs = sig
+            .inputs()
+            .iter()
+            .map(|&ty| gacx.assign_pointer_ids_with_info(ty, PointerInfo::ANNOTATED))
+            .collect::<Vec<_>>();
+        let inputs = gacx.lcx.mk_slice(&inputs);
+        let output = gacx.assign_pointer_ids_with_info(sig.output(), PointerInfo::ANNOTATED);
+        let lsig = LFnSig { inputs, output };
+        gacx.fn_sigs.insert(did, lsig);
+    }
+}
+
+fn mark_foreign_fixed<'tcx>(
+    gacx: &mut GlobalAnalysisCtxt<'tcx>,
+    gasn: &mut GlobalAssignment,
+    tcx: TyCtxt<'tcx>,
+) {
+    // FIX the inputs and outputs of function declarations in extern blocks
+    for (did, lsig) in gacx.fn_sigs.iter() {
+        if tcx.is_foreign_item(did) {
+            make_sig_fixed(gasn, lsig);
+        }
+    }
+
+    // FIX the fields of structs mentioned in extern blocks
+    for adt_did in &gacx.adt_metadata.struct_dids {
+        if gacx.foreign_mentioned_tys.contains(adt_did) {
+            let adt_def = tcx.adt_def(adt_did);
+            let fields = adt_def.all_fields();
+            for field in fields {
+                let field_lty = gacx.field_ltys[&field.did];
+                eprintln!(
+                    "adding FIXED permission for {adt_did:?} field {:?}",
+                    field.did
+                );
+                make_ty_fixed(gasn, field_lty);
+            }
+        }
+    }
+}
+
 fn run(tcx: TyCtxt) {
     let mut gacx = GlobalAnalysisCtxt::new(tcx);
     let mut func_info = HashMap::new();
@@ -520,6 +569,7 @@ fn run(tcx: TyCtxt) {
     // track all types mentioned in extern blocks, we
     // don't want to rewrite those
     gacx.foreign_mentioned_tys = foreign_mentioned_tys(tcx);
+    gather_foreign_sigs(&mut gacx, tcx);
 
     let mut gasn =
         GlobalAssignment::new(gacx.num_pointers(), PermissionSet::UNIQUE, FlagSet::empty());
@@ -529,21 +579,7 @@ fn run(tcx: TyCtxt) {
         }
     }
 
-    // FIX the fields of structs mentioned in extern blocks
-    for adt_did in &gacx.adt_metadata.struct_dids {
-        if gacx.foreign_mentioned_tys.contains(adt_did) {
-            let adt_def = tcx.adt_def(adt_did);
-            let fields = adt_def.all_fields();
-            for field in fields {
-                let field_lty = gacx.field_ltys[&field.did];
-                eprintln!(
-                    "adding FIXED permission for {adt_did:?} field {:?}",
-                    field.did
-                );
-                make_ty_fixed(&mut gasn, field_lty);
-            }
-        }
-    }
+    mark_foreign_fixed(&mut gacx, &mut gasn, tcx);
 
     for info in func_info.values_mut() {
         let num_pointers = info.acx_data.num_pointers();