Substite with NIL_OR_UNDEF_P more

Merged: https://github.com/ruby/ruby/pull/19297

io.c

@@ -7053,7 +7053,7 @@ rb_io_extract_encoding_option(VALUE opt, rb_encoding **enc_p, rb_encoding **enc2
         }
         encoding = Qnil;
     }
-    if (!UNDEF_P(extenc) && !NIL_P(extenc)) {
+    if (!NIL_OR_UNDEF_P(extenc)) {
         extencoding = rb_to_encoding(extenc);
     }
     if (!UNDEF_P(intenc)) {

object.c

@@ -840,7 +840,7 @@ rb_obj_inspect(VALUE obj)
 {
     VALUE ivars = rb_check_funcall(obj, id_instance_variables_to_inspect, 0, 0);
     st_index_t n = 0;
-    if (UNDEF_P(ivars) || NIL_P(ivars)) {
+    if (NIL_OR_UNDEF_P(ivars)) {
         n = rb_ivar_count(obj);
         ivars = Qnil;
     }

string.c

@@ -2155,10 +2155,10 @@ rb_str_init(int argc, VALUE *argv, VALUE str)
         rb_get_kwargs(opt, keyword_ids, 0, 2, kwargs);
         venc = kwargs[0];
         vcapa = kwargs[1];
-        if (!UNDEF_P(venc) && !NIL_P(venc)) {
+        if (!NIL_OR_UNDEF_P(venc)) {
             enc = rb_to_encoding(venc);
         }
-        if (!UNDEF_P(vcapa) && !NIL_P(vcapa)) {
+        if (!NIL_OR_UNDEF_P(vcapa)) {
             rb_len_t capa = NUM2LEN(vcapa);
             rb_len_t len = 0;
             int termlen = enc ? rb_enc_mbminlen(enc) : 1;

transcode.c

@@ -2367,7 +2367,7 @@ transcode_loop_fallback_try(VALUE a)
 
     VALUE ret = args->fallback_func(args->fallback, args->rep);
 
-    if (!UNDEF_P(ret) && !NIL_P(ret)) {
+    if (!NIL_OR_UNDEF_P(ret)) {
         StringValue(ret);
     }
 
@@ -2450,7 +2450,7 @@ transcode_loop(const unsigned char **in_pos, unsigned char **out_pos,
             rb_raise(rb_eRuntimeError, "string modified");
         }
 
-        if (!UNDEF_P(rep) && !NIL_P(rep)) {
+        if (!NIL_OR_UNDEF_P(rep)) {
             ret = rb_econv_insert_output(ec, (const unsigned char *)RSTRING_PTR(rep),
                     RSTRING_LEN(rep), rb_enc_name(rb_enc_get(rep)));
             RB_GC_GUARD(rep); // insert_output may GC while reading rep's bytes