do not use exception runtime when using multi-return, fix segfault in

node by setting stack size and ulimit correctly

wasm/emit_wat.ml

@@ -492,6 +492,7 @@ module Conv = struct
     match e with
     | Var _ | I32 _ | I64 _ | F64 _ | Global_get _ -> true
     | Unop (I31_new, e) -> expr_is_pure e
+    | Let2 { defining_expr; body; _ }
     | Let { defining_expr; body } ->
       expr_is_pure defining_expr && expr_is_pure body
     | _ -> false

wasm/link_wat.ml

@@ -29,13 +29,17 @@ let options =
   [ "--enable-multivalue"
   ; "--enable-gc"
   ; "--enable-reference-types"
-  ; "--enable-exception-handling"
   ; "--enable-tail-call"
-  ]
+  ] @ match Wstate.exception_repr with
+    | Native_exceptions -> [ "--enable-exception-handling" ]
+    | Multi_return ->  []
 
 let wasm_merge = "wasm-merge"
 
-let runtime = [ "exn_tag"; "runtime"; "imports" ]
+let runtime = [  "runtime"; "imports" ]
+  @ match Wstate.exception_repr with
+    | Native_exceptions -> [ "exn_tag" ]
+    | Multi_return ->  []
 
 let merge_files ~runtime_dir ~text files output =
   let text = if text then [ emit_text ] else [] in

wasm/test/test_node.sh

@@ -4,14 +4,18 @@ set -eu
 
 alias time='/usr/bin/time -f"real %e user %U sys %S"'
 
-NODE='node-canary --stack-size=10000'
+ULIMIT_STACK_SIZE=20000
+STACK_SIZE=10000
+NODE="node-canary --stack-size=${STACK_SIZE}"
+
+ulimit -s $ULIMIT_STACK_SIZE
 
 bench() {
   echo "*** Running ${1}"
   echo -n "Wasocaml (node):            "
   ../../ocamlopt -O3 ./${2}.ml > /dev/null
   time $NODE ./main_node.mjs > /dev/null
-  wasm-opt --enable-gc --enable-reference-types --enable-exception-handling --enable-multivalue --enable-tail-call a.out.wasm -o a.out.wasm -O3
+  wasm-opt --enable-gc --enable-reference-types --enable-multivalue --enable-tail-call a.out.wasm -o a.out.wasm -O3
   echo -n "Wasocaml + wasm-opt (node): "
   time $NODE ./main_node.mjs > /dev/null
   echo -n "OCaml native:               "