Add `mrb_get_arg1()` that retrieves single (and only) argument.

`mrb_get_arg1()` raises `ArgumentError` if the method does not receive one
argument.

And replaces all `mrb_get_args(mrb, "o", &arg)` by the new function.

14 files changed, 42 insertions, 84 deletions

diff --git a/mrbgems/mruby-array-ext/src/array.c b/mrbgems/mruby-array-ext/src/array.c
index ab6d99133..0cb61b2ab 100644
--- a/mrbgems/mruby-array-ext/src/array.c
+++ b/mrbgems/mruby-array-ext/src/array.c
@@ -28,9 +28,8 @@ static mrb_value
 mrb_ary_assoc(mrb_state *mrb, mrb_value ary)
 {
   mrb_int i;
-  mrb_value v, k;
-
-  mrb_get_args(mrb, "o", &k);
+  mrb_value v;
+  mrb_value k = mrb_get_arg1(mrb);
 
   for (i = 0; i < RARRAY_LEN(ary); ++i) {
     v = mrb_check_array_type(mrb, RARRAY_PTR(ary)[i]);
@@ -59,9 +58,8 @@ static mrb_value
 mrb_ary_rassoc(mrb_state *mrb, mrb_value ary)
 {
   mrb_int i;
-  mrb_value v, value;
-
-  mrb_get_args(mrb, "o", &value);
+  mrb_value v;
+  mrb_value value = mrb_get_arg1(mrb);
 
   for (i = 0; i < RARRAY_LEN(ary); ++i) {
     v = RARRAY_PTR(ary)[i];
diff --git a/mrbgems/mruby-complex/src/complex.c b/mrbgems/mruby-complex/src/complex.c
index 10fa42a2c..0432da633 100644
--- a/mrbgems/mruby-complex/src/complex.c
+++ b/mrbgems/mruby-complex/src/complex.c
@@ -174,7 +174,7 @@ div_pair(struct float_pair *q, struct float_pair const *a,
 static mrb_value
 complex_div(mrb_state *mrb, mrb_value self)
 {
-  mrb_value rhs;
+  mrb_value rhs = mrb_get_arg1(mrb);
   struct mrb_complex *a, *b;
   struct float_pair ar, ai, br, bi;
   struct float_pair br2, bi2;
@@ -183,7 +183,6 @@ complex_div(mrb_state *mrb, mrb_value self)
   struct float_pair ai_br, ar_bi;
   struct float_pair zr, zi;
 
-  mrb_get_args(mrb, "o", &rhs);
   a = complex_ptr(mrb, self);
   b = complex_ptr(mrb, rhs);
 
diff --git a/mrbgems/mruby-fiber/src/fiber.c b/mrbgems/mruby-fiber/src/fiber.c
index 3c17b59dd..00ee7c223 100644
--- a/mrbgems/mruby-fiber/src/fiber.c
+++ b/mrbgems/mruby-fiber/src/fiber.c
@@ -291,8 +291,7 @@ mrb_fiber_alive_p(mrb_state *mrb, mrb_value self)
 static mrb_value
 fiber_eq(mrb_state *mrb, mrb_value self)
 {
-  mrb_value other;
-  mrb_get_args(mrb, "o", &other);
+  mrb_value other = mrb_get_arg1(mrb);
 
   if (!mrb_fiber_p(other)) {
     return mrb_false_value();
diff --git a/mrbgems/mruby-inline-struct/test/inline.c b/mrbgems/mruby-inline-struct/test/inline.c
index 51804ae31..5d307dcab 100644
--- a/mrbgems/mruby-inline-struct/test/inline.c
+++ b/mrbgems/mruby-inline-struct/test/inline.c
@@ -8,8 +8,7 @@ istruct_test_initialize(mrb_state *mrb, mrb_value self)
 {
   char *string = (char*)mrb_istruct_ptr(self);
   mrb_int size = mrb_istruct_size();
-  mrb_value object;
-  mrb_get_args(mrb, "o", &object);
+  mrb_value object = mrb_get_arg1(mrb);
 
   if (mrb_fixnum_p(object)) {
     strncpy(string, "fixnum", size-1);
@@ -45,8 +44,8 @@ istruct_test_length(mrb_state *mrb, mrb_value self)
 static mrb_value
 istruct_test_test_receive(mrb_state *mrb, mrb_value self)
 {
-  mrb_value object;
-  mrb_get_args(mrb, "o", &object);
+  mrb_value object = mrb_get_arg1(mrb);
+
   if (mrb_obj_class(mrb, object) != mrb_class_get(mrb, "InlineStructTest"))
   {
     mrb_raise(mrb, E_TYPE_ERROR, "Expected InlineStructTest");
diff --git a/mrbgems/mruby-io/src/file.c b/mrbgems/mruby-io/src/file.c
index dd65e2da9..6c99300d8 100644
--- a/mrbgems/mruby-io/src/file.c
+++ b/mrbgems/mruby-io/src/file.c
@@ -492,10 +492,9 @@ mrb_file_truncate(mrb_state *mrb, mrb_value self)
 {
   int fd;
   mrb_int length;
-  mrb_value lenv;
+  mrb_value lenv = mrb_get_arg1(mrb);
 
   fd = mrb_io_fileno(mrb, self);
-  mrb_get_args(mrb, "o", &lenv);
   length = mrb_int(mrb, lenv);
   if (mrb_ftruncate(fd, length) != 0) {
     mrb_raise(mrb, E_IO_ERROR, "ftruncate failed");
diff --git a/mrbgems/mruby-io/src/file_test.c b/mrbgems/mruby-io/src/file_test.c
index 19fd5739b..b7a28f4d3 100644
--- a/mrbgems/mruby-io/src/file_test.c
+++ b/mrbgems/mruby-io/src/file_test.c
@@ -93,9 +93,7 @@ mrb_filetest_s_directory_p(mrb_state *mrb, mrb_value klass)
 #endif
 
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_stat(mrb, obj, &st) < 0)
     return mrb_false_value();
@@ -124,9 +122,7 @@ mrb_filetest_s_pipe_p(mrb_state *mrb, mrb_value klass)
 #  endif
 
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_stat(mrb, obj, &st) < 0)
     return mrb_false_value();
@@ -167,9 +163,7 @@ mrb_filetest_s_symlink_p(mrb_state *mrb, mrb_value klass)
 
 #ifdef S_ISLNK
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_lstat(mrb, obj, &st) == -1)
     return mrb_false_value();
@@ -210,9 +204,7 @@ mrb_filetest_s_socket_p(mrb_state *mrb, mrb_value klass)
 
 #ifdef S_ISSOCK
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_stat(mrb, obj, &st) < 0)
     return mrb_false_value();
@@ -236,9 +228,8 @@ static mrb_value
 mrb_filetest_s_exist_p(mrb_state *mrb, mrb_value klass)
 {
   struct stat st;
-  mrb_value obj;
+  mrb_value obj = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &obj);
   if (mrb_stat(mrb, obj, &st) < 0)
     return mrb_false_value();
 
@@ -261,9 +252,7 @@ mrb_filetest_s_file_p(mrb_state *mrb, mrb_value klass)
 #endif
 
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_stat(mrb, obj, &st) < 0)
     return mrb_false_value();
@@ -285,9 +274,7 @@ static mrb_value
 mrb_filetest_s_zero_p(mrb_state *mrb, mrb_value klass)
 {
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_stat(mrb, obj, &st) < 0)
     return mrb_false_value();
@@ -310,9 +297,7 @@ static mrb_value
 mrb_filetest_s_size(mrb_state *mrb, mrb_value klass)
 {
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_stat(mrb, obj, &st) < 0)
     mrb_sys_fail(mrb, "mrb_stat");
@@ -332,9 +317,7 @@ static mrb_value
 mrb_filetest_s_size_p(mrb_state *mrb, mrb_value klass)
 {
   struct stat st;
-  mrb_value obj;
-
-  mrb_get_args(mrb, "o", &obj);
+  mrb_value obj = mrb_get_arg1(mrb);
 
   if (mrb_stat(mrb, obj, &st) < 0)
     return mrb_nil_value();
diff --git a/mrbgems/mruby-io/src/io.c b/mrbgems/mruby-io/src/io.c
index ef1283b51..505ceb248 100644
--- a/mrbgems/mruby-io/src/io.c
+++ b/mrbgems/mruby-io/src/io.c
@@ -599,13 +599,12 @@ mrb_dup(mrb_state *mrb, int fd, mrb_bool *failed)
 static mrb_value
 mrb_io_initialize_copy(mrb_state *mrb, mrb_value copy)
 {
-  mrb_value orig;
+  mrb_value orig = mrb_get_arg1(mrb);
   mrb_value buf;
   struct mrb_io *fptr_copy;
   struct mrb_io *fptr_orig;
   mrb_bool failed = TRUE;
 
-  mrb_get_args(mrb, "o", &orig);
   fptr_orig = io_get_open_fptr(mrb, orig);
   fptr_copy = (struct mrb_io *)DATA_PTR(copy);
   if (fptr_orig == fptr_copy) return copy;
diff --git a/mrbgems/mruby-kernel-ext/src/kernel.c b/mrbgems/mruby-kernel-ext/src/kernel.c
index 427740c1c..1d183aecd 100644
--- a/mrbgems/mruby-kernel-ext/src/kernel.c
+++ b/mrbgems/mruby-kernel-ext/src/kernel.c
@@ -128,9 +128,8 @@ mrb_f_integer(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_f_float(mrb_state *mrb, mrb_value self)
 {
-  mrb_value arg;
+  mrb_value arg = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &arg);
   return mrb_Float(mrb, arg);
 }
 #endif
@@ -149,9 +148,9 @@ mrb_f_float(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_f_string(mrb_state *mrb, mrb_value self)
 {
-  mrb_value arg, tmp;
+  mrb_value arg = mrb_get_arg1(mrb);
+  mrb_value tmp;
 
-  mrb_get_args(mrb, "o", &arg);
   tmp = mrb_convert_type(mrb, arg, MRB_TT_STRING, "String", "to_s");
   return tmp;
 }
@@ -168,9 +167,9 @@ mrb_f_string(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_f_array(mrb_state *mrb, mrb_value self)
 {
-  mrb_value arg, tmp;
+  mrb_value arg = mrb_get_arg1(mrb);
+  mrb_value tmp;
 
-  mrb_get_args(mrb, "o", &arg);
   tmp = mrb_check_convert_type(mrb, arg, MRB_TT_ARRAY, "Array", "to_a");
   if (mrb_nil_p(tmp)) {
     return mrb_ary_new_from_values(mrb, 1, &arg);
@@ -196,9 +195,8 @@ mrb_f_array(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_f_hash(mrb_state *mrb, mrb_value self)
 {
-  mrb_value arg;
+  mrb_value arg = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &arg);
   if (mrb_nil_p(arg) || (mrb_array_p(arg) && RARRAY_LEN(arg) == 0)) {
     return mrb_hash_new(mrb);
   }
diff --git a/mrbgems/mruby-method/src/method.c b/mrbgems/mruby-method/src/method.c
index d249b463b..111b031b9 100644
--- a/mrbgems/mruby-method/src/method.c
+++ b/mrbgems/mruby-method/src/method.c
@@ -33,9 +33,8 @@ unbound_method_bind(mrb_state *mrb, mrb_value self)
   mrb_value name = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "_name"));
   mrb_value proc = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "_proc"));
   mrb_value klass = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "_klass"));
-  mrb_value recv;
+  mrb_value recv = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &recv);
   bind_check(mrb, recv, owner);
   me = method_object_alloc(mrb, mrb_class_get(mrb, "Method"));
   mrb_obj_iv_set(mrb, me, mrb_intern_lit(mrb, "_owner"), owner);
@@ -51,11 +50,11 @@ unbound_method_bind(mrb_state *mrb, mrb_value self)
 static mrb_value
 method_eql(mrb_state *mrb, mrb_value self)
 {
-  mrb_value other, receiver, orig_proc, other_proc;
+  mrb_value other = mrb_get_arg1(mrb);
+  mrb_value receiver, orig_proc, other_proc;
   struct RClass *owner, *klass;
   struct RProc *orig_rproc, *other_rproc;
 
-  mrb_get_args(mrb, "o", &other);
   if (!mrb_obj_is_instance_of(mrb, other, mrb_class(mrb, self)))
     return mrb_false_value();
 
diff --git a/mrbgems/mruby-print/src/print.c b/mrbgems/mruby-print/src/print.c
index 66d070f60..9301dbe55 100644
--- a/mrbgems/mruby-print/src/print.c
+++ b/mrbgems/mruby-print/src/print.c
@@ -45,9 +45,8 @@ printstr(mrb_state *mrb, mrb_value obj)
 mrb_value
 mrb_printstr(mrb_state *mrb, mrb_value self)
 {
-  mrb_value argv;
+  mrb_value argv = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &argv);
   printstr(mrb, argv);
 
   return argv;
diff --git a/mrbgems/mruby-range-ext/src/range.c b/mrbgems/mruby-range-ext/src/range.c
index 36b684fad..2a0b4e97d 100644
--- a/mrbgems/mruby-range-ext/src/range.c
+++ b/mrbgems/mruby-range-ext/src/range.c
@@ -34,12 +34,10 @@ r_lt(mrb_state *mrb, mrb_value a, mrb_value b)
 static mrb_value
 range_cover(mrb_state *mrb, mrb_value range)
 {
-  mrb_value val;
   struct RRange *r = mrb_range_ptr(mrb, range);
+  mrb_value val = mrb_get_arg1(mrb);
   mrb_value beg, end;
 
-  mrb_get_args(mrb, "o", &val);
-
   beg = RANGE_BEG(r);
   end = RANGE_END(r);
 
diff --git a/mrbgems/mruby-string-ext/src/string.c b/mrbgems/mruby-string-ext/src/string.c
index ea9508be0..7cf146ec8 100644
--- a/mrbgems/mruby-string-ext/src/string.c
+++ b/mrbgems/mruby-string-ext/src/string.c
@@ -164,9 +164,8 @@ mrb_str_swapcase(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_str_concat_m(mrb_state *mrb, mrb_value self)
 {
-  mrb_value str;
+  mrb_value str = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &str);
   if (mrb_fixnum_p(str) || mrb_float_p(str))
 #ifdef MRB_UTF8_STRING
     str = int_chr_utf8(mrb, str);
diff --git a/mrbgems/mruby-struct/src/struct.c b/mrbgems/mruby-struct/src/struct.c
index f42a5f1ea..7fbf9225f 100644
--- a/mrbgems/mruby-struct/src/struct.c
+++ b/mrbgems/mruby-struct/src/struct.c
@@ -154,9 +154,8 @@ mrb_struct_set_m(mrb_state *mrb, mrb_value obj)
 {
   mrb_int i = mrb_fixnum(mrb_proc_cfunc_env_get(mrb, 0));
   mrb_value *ptr;
-  mrb_value val;
+  mrb_value val = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &val);
   mrb_struct_modify(mrb, obj);
   ptr = RSTRUCT_PTR(obj);
   if (ptr == NULL || i >= RSTRUCT_LEN(obj)) {
@@ -356,9 +355,7 @@ mrb_struct_initialize(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_struct_init_copy(mrb_state *mrb, mrb_value copy)
 {
-  mrb_value s;
-
-  mrb_get_args(mrb, "o", &s);
+  mrb_value s = mrb_get_arg1(mrb);
 
   if (mrb_obj_equal(mrb, copy, s)) return copy;
   if (!mrb_obj_is_instance_of(mrb, s, mrb_obj_class(mrb, copy))) {
@@ -428,9 +425,8 @@ struct_aref_int(mrb_state *mrb, mrb_value s, mrb_int i)
 static mrb_value
 mrb_struct_aref(mrb_state *mrb, mrb_value s)
 {
-  mrb_value idx;
+  mrb_value idx = mrb_get_arg1(mrb);
 
-  mrb_get_args(mrb, "o", &idx);
   if (mrb_string_p(idx)) {
     mrb_value sym = mrb_check_intern_str(mrb, idx);
 
@@ -545,11 +541,10 @@ mrb_struct_aset(mrb_state *mrb, mrb_value s)
 static mrb_value
 mrb_struct_equal(mrb_state *mrb, mrb_value s)
 {
-  mrb_value s2;
+  mrb_value s2 = mrb_get_arg1(mrb);
   mrb_value *ptr, *ptr2;
   mrb_int i, len;
 
-  mrb_get_args(mrb, "o", &s2);
   if (mrb_obj_equal(mrb, s, s2)) {
     return mrb_true_value();
   }
@@ -582,11 +577,10 @@ mrb_struct_equal(mrb_state *mrb, mrb_value s)
 static mrb_value
 mrb_struct_eql(mrb_state *mrb, mrb_value s)
 {
-  mrb_value s2;
+  mrb_value s2 = mrb_get_arg1(mrb);
   mrb_value *ptr, *ptr2;
   mrb_int i, len;
 
-  mrb_get_args(mrb, "o", &s2);
   if (mrb_obj_equal(mrb, s, s2)) {
     return mrb_true_value();
   }
diff --git a/mrbgems/mruby-time/src/time.c b/mrbgems/mruby-time/src/time.c
index e76e11649..5fa700848 100644
--- a/mrbgems/mruby-time/src/time.c
+++ b/mrbgems/mruby-time/src/time.c
@@ -515,11 +515,10 @@ time_get_ptr(mrb_state *mrb, mrb_value time)
 static mrb_value
 mrb_time_eq(mrb_state *mrb, mrb_value self)
 {
-  mrb_value other;
+  mrb_value other = mrb_get_arg1(mrb);
   struct mrb_time *tm1, *tm2;
   mrb_bool eq_p;
 
-  mrb_get_args(mrb, "o", &other);
   tm1 = DATA_GET_PTR(mrb, self, &mrb_time_type, struct mrb_time);
   tm2 = DATA_CHECK_GET_PTR(mrb, other, &mrb_time_type, struct mrb_time);
   eq_p = tm1 && tm2 && tm1->sec == tm2->sec && tm1->usec == tm2->usec;
@@ -530,10 +529,9 @@ mrb_time_eq(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_time_cmp(mrb_state *mrb, mrb_value self)
 {
-  mrb_value other;
+  mrb_value other = mrb_get_arg1(mrb);
   struct mrb_time *tm1, *tm2;
 
-  mrb_get_args(mrb, "o", &other);
   tm1 = DATA_GET_PTR(mrb, self, &mrb_time_type, struct mrb_time);
   tm2 = DATA_CHECK_GET_PTR(mrb, other, &mrb_time_type, struct mrb_time);
   if (!tm1 || !tm2) return mrb_nil_value();
@@ -556,11 +554,10 @@ mrb_time_cmp(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_time_plus(mrb_state *mrb, mrb_value self)
 {
-  mrb_value o;
+  mrb_value o = mrb_get_arg1(mrb);
   struct mrb_time *tm;
   time_t sec, usec;
 
-  mrb_get_args(mrb, "o", &o);
   tm = time_get_ptr(mrb, self);
   sec = mrb_to_time_t(mrb, o, &usec);
   return mrb_time_make_time(mrb, mrb_obj_class(mrb, self), tm->sec+sec, tm->usec+usec, tm->timezone);
@@ -569,10 +566,9 @@ mrb_time_plus(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_time_minus(mrb_state *mrb, mrb_value self)
 {
-  mrb_value other;
+  mrb_value other = mrb_get_arg1(mrb);
   struct mrb_time *tm, *tm2;
 
-  mrb_get_args(mrb, "o", &other);
   tm = time_get_ptr(mrb, self);
   tm2 = DATA_CHECK_GET_PTR(mrb, other, &mrb_time_type, struct mrb_time);
   if (tm2) {
@@ -770,10 +766,9 @@ mrb_time_initialize(mrb_state *mrb, mrb_value self)
 static mrb_value
 mrb_time_initialize_copy(mrb_state *mrb, mrb_value copy)
 {
-  mrb_value src;
+  mrb_value src = mrb_get_arg1(mrb);
   struct mrb_time *t1, *t2;
 
-  mrb_get_args(mrb, "o", &src);
   if (mrb_obj_equal(mrb, copy, src)) return copy;
   if (!mrb_obj_is_instance_of(mrb, src, mrb_obj_class(mrb, copy))) {
     mrb_raise(mrb, E_TYPE_ERROR, "wrong argument class");