Fix equality comparisons for variants in C

Makes sure equality comparisons for variants are compiled correctly. Needed for CHERI and mips, which have structs containing
variants. Also make sure that struct equality works for structs containing other structs.

1 files changed, 18 insertions, 4 deletions

diff --git a/src/c_backend.ml b/src/c_backend.ml
index 6097e996..09501ce9 100644
--- a/src/c_backend.ml
+++ b/src/c_backend.ml
@@ -2121,10 +2121,7 @@ let codegen_type_def ctx = function
      in
      let codegen_eq =
        let codegen_eq_test (id, ctyp) =
-         if is_stack_ctyp ctyp then
-           string (Printf.sprintf "op1.%s == op2.%s" (sgen_id id) (sgen_id id))
-         else
-           string (Printf.sprintf "EQUAL(%s)(op1.%s, op2.%s)" (sgen_ctyp_name ctyp) (sgen_id id) (sgen_id id))
+         string (Printf.sprintf "EQUAL(%s)(op1.%s, op2.%s)" (sgen_ctyp_name ctyp) (sgen_id id) (sgen_id id))
        in
        string (Printf.sprintf "static bool EQUAL(%s)(struct %s op1, struct %s op2)" (sgen_id id) (sgen_id id) (sgen_id id))
        ^^ space
@@ -2245,6 +2242,21 @@ let codegen_type_def ctx = function
                     ^^ each_ctor "op." set_field tus)
                    rbrace
      in
+     let codegen_eq =
+       let codegen_eq_test ctor_id ctyp =
+         string (Printf.sprintf "return EQUAL(%s)(op1.%s, op2.%s);" (sgen_ctyp_name ctyp) (sgen_id ctor_id) (sgen_id ctor_id))
+       in
+       let rec codegen_eq_tests = function
+         | [] -> string "return false;"
+         | (ctor_id, ctyp) :: ctors ->
+            string (Printf.sprintf "if (op1.kind == Kind_%s && op2.kind == Kind_%s) " (sgen_id ctor_id) (sgen_id ctor_id)) ^^ lbrace ^^ hardline
+            ^^ jump 0 2 (codegen_eq_test ctor_id ctyp)
+            ^^ hardline ^^ rbrace ^^ string " else " ^^ codegen_eq_tests ctors
+       in
+       let n = sgen_id id in
+       string (Printf.sprintf "static bool EQUAL(%s)(struct %s op1, struct %s op2) " n n n)
+       ^^ surround 2 0 lbrace (codegen_eq_tests tus) rbrace
+     in
      string (Printf.sprintf "// union %s" (string_of_id id)) ^^ hardline
      ^^ string "enum" ^^ space
      ^^ string ("kind_" ^ sgen_id id) ^^ space
@@ -2272,6 +2284,8 @@ let codegen_type_def ctx = function
      ^^ twice hardline
      ^^ codegen_setter
      ^^ twice hardline
+     ^^ codegen_eq
+     ^^ twice hardline
      ^^ separate_map (twice hardline) codegen_ctor tus
      (* If this is the exception type, then we setup up some global variables to deal with exceptions. *)
      ^^ if string_of_id id = "exception" then