1 /* Fortran language support routines for GDB, the GNU debugger.
3 Copyright (C) 1993-2020 Free Software Foundation, Inc.
5 Contributed by Motorola. Adapted from the C parser by Farooq Butt
6 (fmbutt@engage.sps.mot.com).
8 This file is part of GDB.
10 This program is free software; you can redistribute it and/or modify
11 it under the terms of the GNU General Public License as published by
12 the Free Software Foundation; either version 3 of the License, or
13 (at your option) any later version.
15 This program is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
20 You should have received a copy of the GNU General Public License
21 along with this program. If not, see <http://www.gnu.org/licenses/>. */
26 #include "expression.h"
27 #include "parser-defs.h"
34 #include "cp-support.h"
37 #include "target-float.h"
44 static void f_printchar (int c
, struct type
*type
, struct ui_file
* stream
);
45 static void f_emit_char (int c
, struct type
*type
,
46 struct ui_file
* stream
, int quoter
);
48 /* Return the encoding that should be used for the character type
52 f_get_encoding (struct type
*type
)
56 switch (TYPE_LENGTH (type
))
59 encoding
= target_charset (get_type_arch (type
));
62 if (type_byte_order (type
) == BFD_ENDIAN_BIG
)
63 encoding
= "UTF-32BE";
65 encoding
= "UTF-32LE";
69 error (_("unrecognized character type"));
75 /* Print the character C on STREAM as part of the contents of a literal
76 string whose delimiter is QUOTER. Note that that format for printing
77 characters and strings is language specific.
78 FIXME: This is a copy of the same function from c-exp.y. It should
79 be replaced with a true F77 version. */
82 f_emit_char (int c
, struct type
*type
, struct ui_file
*stream
, int quoter
)
84 const char *encoding
= f_get_encoding (type
);
86 generic_emit_char (c
, type
, stream
, quoter
, encoding
);
89 /* Implementation of la_printchar. */
92 f_printchar (int c
, struct type
*type
, struct ui_file
*stream
)
94 fputs_filtered ("'", stream
);
95 LA_EMIT_CHAR (c
, type
, stream
, '\'');
96 fputs_filtered ("'", stream
);
99 /* Print the character string STRING, printing at most LENGTH characters.
100 Printing stops early if the number hits print_max; repeat counts
101 are printed as appropriate. Print ellipses at the end if we
102 had to stop before printing LENGTH characters, or if FORCE_ELLIPSES.
103 FIXME: This is a copy of the same function from c-exp.y. It should
104 be replaced with a true F77 version. */
107 f_printstr (struct ui_file
*stream
, struct type
*type
, const gdb_byte
*string
,
108 unsigned int length
, const char *encoding
, int force_ellipses
,
109 const struct value_print_options
*options
)
111 const char *type_encoding
= f_get_encoding (type
);
113 if (TYPE_LENGTH (type
) == 4)
114 fputs_filtered ("4_", stream
);
116 if (!encoding
|| !*encoding
)
117 encoding
= type_encoding
;
119 generic_printstr (stream
, type
, string
, length
, encoding
,
120 force_ellipses
, '\'', 0, options
);
124 /* Table of operators and their precedences for printing expressions. */
126 static const struct op_print f_op_print_tab
[] =
128 {"+", BINOP_ADD
, PREC_ADD
, 0},
129 {"+", UNOP_PLUS
, PREC_PREFIX
, 0},
130 {"-", BINOP_SUB
, PREC_ADD
, 0},
131 {"-", UNOP_NEG
, PREC_PREFIX
, 0},
132 {"*", BINOP_MUL
, PREC_MUL
, 0},
133 {"/", BINOP_DIV
, PREC_MUL
, 0},
134 {"DIV", BINOP_INTDIV
, PREC_MUL
, 0},
135 {"MOD", BINOP_REM
, PREC_MUL
, 0},
136 {"=", BINOP_ASSIGN
, PREC_ASSIGN
, 1},
137 {".OR.", BINOP_LOGICAL_OR
, PREC_LOGICAL_OR
, 0},
138 {".AND.", BINOP_LOGICAL_AND
, PREC_LOGICAL_AND
, 0},
139 {".NOT.", UNOP_LOGICAL_NOT
, PREC_PREFIX
, 0},
140 {".EQ.", BINOP_EQUAL
, PREC_EQUAL
, 0},
141 {".NE.", BINOP_NOTEQUAL
, PREC_EQUAL
, 0},
142 {".LE.", BINOP_LEQ
, PREC_ORDER
, 0},
143 {".GE.", BINOP_GEQ
, PREC_ORDER
, 0},
144 {".GT.", BINOP_GTR
, PREC_ORDER
, 0},
145 {".LT.", BINOP_LESS
, PREC_ORDER
, 0},
146 {"**", UNOP_IND
, PREC_PREFIX
, 0},
147 {"@", BINOP_REPEAT
, PREC_REPEAT
, 0},
148 {NULL
, OP_NULL
, PREC_REPEAT
, 0}
151 enum f_primitive_types
{
152 f_primitive_type_character
,
153 f_primitive_type_logical
,
154 f_primitive_type_logical_s1
,
155 f_primitive_type_logical_s2
,
156 f_primitive_type_logical_s8
,
157 f_primitive_type_integer
,
158 f_primitive_type_integer_s2
,
159 f_primitive_type_real
,
160 f_primitive_type_real_s8
,
161 f_primitive_type_real_s16
,
162 f_primitive_type_complex_s8
,
163 f_primitive_type_complex_s16
,
164 f_primitive_type_void
,
169 f_language_arch_info (struct gdbarch
*gdbarch
,
170 struct language_arch_info
*lai
)
172 const struct builtin_f_type
*builtin
= builtin_f_type (gdbarch
);
174 lai
->string_char_type
= builtin
->builtin_character
;
175 lai
->primitive_type_vector
176 = GDBARCH_OBSTACK_CALLOC (gdbarch
, nr_f_primitive_types
+ 1,
179 lai
->primitive_type_vector
[f_primitive_type_character
]
180 = builtin
->builtin_character
;
181 lai
->primitive_type_vector
[f_primitive_type_logical
]
182 = builtin
->builtin_logical
;
183 lai
->primitive_type_vector
[f_primitive_type_logical_s1
]
184 = builtin
->builtin_logical_s1
;
185 lai
->primitive_type_vector
[f_primitive_type_logical_s2
]
186 = builtin
->builtin_logical_s2
;
187 lai
->primitive_type_vector
[f_primitive_type_logical_s8
]
188 = builtin
->builtin_logical_s8
;
189 lai
->primitive_type_vector
[f_primitive_type_real
]
190 = builtin
->builtin_real
;
191 lai
->primitive_type_vector
[f_primitive_type_real_s8
]
192 = builtin
->builtin_real_s8
;
193 lai
->primitive_type_vector
[f_primitive_type_real_s16
]
194 = builtin
->builtin_real_s16
;
195 lai
->primitive_type_vector
[f_primitive_type_complex_s8
]
196 = builtin
->builtin_complex_s8
;
197 lai
->primitive_type_vector
[f_primitive_type_complex_s16
]
198 = builtin
->builtin_complex_s16
;
199 lai
->primitive_type_vector
[f_primitive_type_void
]
200 = builtin
->builtin_void
;
202 lai
->bool_type_symbol
= "logical";
203 lai
->bool_type_default
= builtin
->builtin_logical_s2
;
206 /* Remove the modules separator :: from the default break list. */
209 f_word_break_characters (void)
217 retval
= xstrdup (default_word_break_characters ());
218 s
= strchr (retval
, ':');
221 char *last_char
= &s
[strlen (s
) - 1];
230 /* Consider the modules separator :: as a valid symbol name character
234 f_collect_symbol_completion_matches (completion_tracker
&tracker
,
235 complete_symbol_mode mode
,
236 symbol_name_match_type compare_name
,
237 const char *text
, const char *word
,
240 default_collect_symbol_completion_matches_break_on (tracker
, mode
,
242 text
, word
, ":", code
);
245 /* Special expression evaluation cases for Fortran. */
247 static struct value
*
248 evaluate_subexp_f (struct type
*expect_type
, struct expression
*exp
,
249 int *pos
, enum noside noside
)
251 struct value
*arg1
= NULL
, *arg2
= NULL
;
258 op
= exp
->elts
[pc
].opcode
;
264 return evaluate_subexp_standard (expect_type
, exp
, pos
, noside
);
267 arg1
= evaluate_subexp (NULL_TYPE
, exp
, pos
, noside
);
268 if (noside
== EVAL_SKIP
)
269 return eval_skip_value (exp
);
270 type
= value_type (arg1
);
271 switch (type
->code ())
276 = fabs (target_float_to_host_double (value_contents (arg1
),
278 return value_from_host_double (type
, d
);
282 LONGEST l
= value_as_long (arg1
);
284 return value_from_longest (type
, l
);
287 error (_("ABS of type %s not supported"), TYPE_SAFE_NAME (type
));
290 arg1
= evaluate_subexp (NULL_TYPE
, exp
, pos
, noside
);
291 arg2
= evaluate_subexp (value_type (arg1
), exp
, pos
, noside
);
292 if (noside
== EVAL_SKIP
)
293 return eval_skip_value (exp
);
294 type
= value_type (arg1
);
295 if (type
->code () != value_type (arg2
)->code ())
296 error (_("non-matching types for parameters to MOD ()"));
297 switch (type
->code ())
302 = target_float_to_host_double (value_contents (arg1
),
305 = target_float_to_host_double (value_contents (arg2
),
307 double d3
= fmod (d1
, d2
);
308 return value_from_host_double (type
, d3
);
312 LONGEST v1
= value_as_long (arg1
);
313 LONGEST v2
= value_as_long (arg2
);
315 error (_("calling MOD (N, 0) is undefined"));
316 LONGEST v3
= v1
- (v1
/ v2
) * v2
;
317 return value_from_longest (value_type (arg1
), v3
);
320 error (_("MOD of type %s not supported"), TYPE_SAFE_NAME (type
));
322 case UNOP_FORTRAN_CEILING
:
324 arg1
= evaluate_subexp (NULL_TYPE
, exp
, pos
, noside
);
325 if (noside
== EVAL_SKIP
)
326 return eval_skip_value (exp
);
327 type
= value_type (arg1
);
328 if (type
->code () != TYPE_CODE_FLT
)
329 error (_("argument to CEILING must be of type float"));
331 = target_float_to_host_double (value_contents (arg1
),
334 return value_from_host_double (type
, val
);
337 case UNOP_FORTRAN_FLOOR
:
339 arg1
= evaluate_subexp (NULL_TYPE
, exp
, pos
, noside
);
340 if (noside
== EVAL_SKIP
)
341 return eval_skip_value (exp
);
342 type
= value_type (arg1
);
343 if (type
->code () != TYPE_CODE_FLT
)
344 error (_("argument to FLOOR must be of type float"));
346 = target_float_to_host_double (value_contents (arg1
),
349 return value_from_host_double (type
, val
);
352 case BINOP_FORTRAN_MODULO
:
354 arg1
= evaluate_subexp (NULL_TYPE
, exp
, pos
, noside
);
355 arg2
= evaluate_subexp (value_type (arg1
), exp
, pos
, noside
);
356 if (noside
== EVAL_SKIP
)
357 return eval_skip_value (exp
);
358 type
= value_type (arg1
);
359 if (type
->code () != value_type (arg2
)->code ())
360 error (_("non-matching types for parameters to MODULO ()"));
361 /* MODULO(A, P) = A - FLOOR (A / P) * P */
362 switch (type
->code ())
366 LONGEST a
= value_as_long (arg1
);
367 LONGEST p
= value_as_long (arg2
);
368 LONGEST result
= a
- (a
/ p
) * p
;
369 if (result
!= 0 && (a
< 0) != (p
< 0))
371 return value_from_longest (value_type (arg1
), result
);
376 = target_float_to_host_double (value_contents (arg1
),
379 = target_float_to_host_double (value_contents (arg2
),
381 double result
= fmod (a
, p
);
382 if (result
!= 0 && (a
< 0.0) != (p
< 0.0))
384 return value_from_host_double (type
, result
);
387 error (_("MODULO of type %s not supported"), TYPE_SAFE_NAME (type
));
390 case BINOP_FORTRAN_CMPLX
:
391 arg1
= evaluate_subexp (NULL_TYPE
, exp
, pos
, noside
);
392 arg2
= evaluate_subexp (value_type (arg1
), exp
, pos
, noside
);
393 if (noside
== EVAL_SKIP
)
394 return eval_skip_value (exp
);
395 type
= builtin_f_type(exp
->gdbarch
)->builtin_complex_s16
;
396 return value_literal_complex (arg1
, arg2
, type
);
398 case UNOP_FORTRAN_KIND
:
399 arg1
= evaluate_subexp (NULL
, exp
, pos
, EVAL_AVOID_SIDE_EFFECTS
);
400 type
= value_type (arg1
);
402 switch (type
->code ())
404 case TYPE_CODE_STRUCT
:
405 case TYPE_CODE_UNION
:
406 case TYPE_CODE_MODULE
:
408 error (_("argument to kind must be an intrinsic type"));
411 if (!TYPE_TARGET_TYPE (type
))
412 return value_from_longest (builtin_type (exp
->gdbarch
)->builtin_int
,
414 return value_from_longest (builtin_type (exp
->gdbarch
)->builtin_int
,
415 TYPE_LENGTH (TYPE_TARGET_TYPE (type
)));
418 /* Should be unreachable. */
422 /* Return true if TYPE is a string. */
425 f_is_string_type_p (struct type
*type
)
427 type
= check_typedef (type
);
428 return (type
->code () == TYPE_CODE_STRING
429 || (type
->code () == TYPE_CODE_ARRAY
430 && TYPE_TARGET_TYPE (type
)->code () == TYPE_CODE_CHAR
));
433 /* Special expression lengths for Fortran. */
436 operator_length_f (const struct expression
*exp
, int pc
, int *oplenp
,
442 switch (exp
->elts
[pc
- 1].opcode
)
445 operator_length_standard (exp
, pc
, oplenp
, argsp
);
448 case UNOP_FORTRAN_KIND
:
449 case UNOP_FORTRAN_FLOOR
:
450 case UNOP_FORTRAN_CEILING
:
455 case BINOP_FORTRAN_CMPLX
:
456 case BINOP_FORTRAN_MODULO
:
466 /* Helper for PRINT_SUBEXP_F. Arguments are as for PRINT_SUBEXP_F, except
467 the extra argument NAME which is the text that should be printed as the
468 name of this operation. */
471 print_unop_subexp_f (struct expression
*exp
, int *pos
,
472 struct ui_file
*stream
, enum precedence prec
,
476 fprintf_filtered (stream
, "%s(", name
);
477 print_subexp (exp
, pos
, stream
, PREC_SUFFIX
);
478 fputs_filtered (")", stream
);
481 /* Helper for PRINT_SUBEXP_F. Arguments are as for PRINT_SUBEXP_F, except
482 the extra argument NAME which is the text that should be printed as the
483 name of this operation. */
486 print_binop_subexp_f (struct expression
*exp
, int *pos
,
487 struct ui_file
*stream
, enum precedence prec
,
491 fprintf_filtered (stream
, "%s(", name
);
492 print_subexp (exp
, pos
, stream
, PREC_SUFFIX
);
493 fputs_filtered (",", stream
);
494 print_subexp (exp
, pos
, stream
, PREC_SUFFIX
);
495 fputs_filtered (")", stream
);
498 /* Special expression printing for Fortran. */
501 print_subexp_f (struct expression
*exp
, int *pos
,
502 struct ui_file
*stream
, enum precedence prec
)
505 enum exp_opcode op
= exp
->elts
[pc
].opcode
;
510 print_subexp_standard (exp
, pos
, stream
, prec
);
513 case UNOP_FORTRAN_KIND
:
514 print_unop_subexp_f (exp
, pos
, stream
, prec
, "KIND");
517 case UNOP_FORTRAN_FLOOR
:
518 print_unop_subexp_f (exp
, pos
, stream
, prec
, "FLOOR");
521 case UNOP_FORTRAN_CEILING
:
522 print_unop_subexp_f (exp
, pos
, stream
, prec
, "CEILING");
525 case BINOP_FORTRAN_CMPLX
:
526 print_binop_subexp_f (exp
, pos
, stream
, prec
, "CMPLX");
529 case BINOP_FORTRAN_MODULO
:
530 print_binop_subexp_f (exp
, pos
, stream
, prec
, "MODULO");
535 /* Special expression names for Fortran. */
538 op_name_f (enum exp_opcode opcode
)
543 return op_name_standard (opcode
);
548 #include "fortran-operator.def"
553 /* Special expression dumping for Fortran. */
556 dump_subexp_body_f (struct expression
*exp
,
557 struct ui_file
*stream
, int elt
)
559 int opcode
= exp
->elts
[elt
].opcode
;
565 return dump_subexp_body_standard (exp
, stream
, elt
);
567 case UNOP_FORTRAN_KIND
:
568 case UNOP_FORTRAN_FLOOR
:
569 case UNOP_FORTRAN_CEILING
:
570 case BINOP_FORTRAN_CMPLX
:
571 case BINOP_FORTRAN_MODULO
:
572 operator_length_f (exp
, (elt
+ 1), &oplen
, &nargs
);
577 for (i
= 0; i
< nargs
; i
+= 1)
578 elt
= dump_subexp (exp
, stream
, elt
);
583 /* Special expression checking for Fortran. */
586 operator_check_f (struct expression
*exp
, int pos
,
587 int (*objfile_func
) (struct objfile
*objfile
,
591 const union exp_element
*const elts
= exp
->elts
;
593 switch (elts
[pos
].opcode
)
595 case UNOP_FORTRAN_KIND
:
596 case UNOP_FORTRAN_FLOOR
:
597 case UNOP_FORTRAN_CEILING
:
598 case BINOP_FORTRAN_CMPLX
:
599 case BINOP_FORTRAN_MODULO
:
600 /* Any references to objfiles are held in the arguments to this
601 expression, not within the expression itself, so no additional
602 checking is required here, the outer expression iteration code
603 will take care of checking each argument. */
607 return operator_check_standard (exp
, pos
, objfile_func
, data
);
613 static const char *f_extensions
[] =
615 ".f", ".F", ".for", ".FOR", ".ftn", ".FTN", ".fpp", ".FPP",
616 ".f90", ".F90", ".f95", ".F95", ".f03", ".F03", ".f08", ".F08",
620 /* Expression processing for Fortran. */
621 static const struct exp_descriptor exp_descriptor_f
=
631 extern const struct language_defn f_language_defn
=
642 f_parse
, /* parser */
644 f_printchar
, /* Print character constant */
645 f_printstr
, /* function to print string constant */
646 f_emit_char
, /* Function to print a single character */
647 f_print_type
, /* Print a type using appropriate syntax */
648 f_print_typedef
, /* Print a typedef using appropriate syntax */
649 f_value_print_innner
, /* la_value_print_inner */
650 c_value_print
, /* FIXME */
651 default_read_var_value
, /* la_read_var_value */
652 NULL
, /* Language specific skip_trampoline */
653 NULL
, /* name_of_this */
654 false, /* la_store_sym_names_in_linkage_form_p */
655 cp_lookup_symbol_nonlocal
, /* lookup_symbol_nonlocal */
656 basic_lookup_transparent_type
,/* lookup_transparent_type */
658 /* We could support demangling here to provide module namespaces
659 also for inferiors with only minimal symbol table (ELF symbols).
660 Just the mangling standard is not standardized across compilers
661 and there is no DW_AT_producer available for inferiors with only
662 the ELF symbols to check the mangling kind. */
663 NULL
, /* Language specific symbol demangler */
665 NULL
, /* Language specific
666 class_name_from_physname */
667 f_op_print_tab
, /* expression operators for printing */
668 0, /* arrays are first-class (not c-style) */
669 1, /* String lower bound */
670 f_word_break_characters
,
671 f_collect_symbol_completion_matches
,
672 f_language_arch_info
,
673 default_print_array_index
,
674 default_pass_by_reference
,
675 c_watch_location_expression
,
676 cp_get_symbol_name_matcher
, /* la_get_symbol_name_matcher */
677 iterate_over_symbols
,
683 "(...)" /* la_struct_too_deep_ellipsis */
687 build_fortran_types (struct gdbarch
*gdbarch
)
689 struct builtin_f_type
*builtin_f_type
690 = GDBARCH_OBSTACK_ZALLOC (gdbarch
, struct builtin_f_type
);
692 builtin_f_type
->builtin_void
693 = arch_type (gdbarch
, TYPE_CODE_VOID
, TARGET_CHAR_BIT
, "void");
695 builtin_f_type
->builtin_character
696 = arch_type (gdbarch
, TYPE_CODE_CHAR
, TARGET_CHAR_BIT
, "character");
698 builtin_f_type
->builtin_logical_s1
699 = arch_boolean_type (gdbarch
, TARGET_CHAR_BIT
, 1, "logical*1");
701 builtin_f_type
->builtin_integer_s2
702 = arch_integer_type (gdbarch
, gdbarch_short_bit (gdbarch
), 0,
705 builtin_f_type
->builtin_integer_s8
706 = arch_integer_type (gdbarch
, gdbarch_long_long_bit (gdbarch
), 0,
709 builtin_f_type
->builtin_logical_s2
710 = arch_boolean_type (gdbarch
, gdbarch_short_bit (gdbarch
), 1,
713 builtin_f_type
->builtin_logical_s8
714 = arch_boolean_type (gdbarch
, gdbarch_long_long_bit (gdbarch
), 1,
717 builtin_f_type
->builtin_integer
718 = arch_integer_type (gdbarch
, gdbarch_int_bit (gdbarch
), 0,
721 builtin_f_type
->builtin_logical
722 = arch_boolean_type (gdbarch
, gdbarch_int_bit (gdbarch
), 1,
725 builtin_f_type
->builtin_real
726 = arch_float_type (gdbarch
, gdbarch_float_bit (gdbarch
),
727 "real", gdbarch_float_format (gdbarch
));
728 builtin_f_type
->builtin_real_s8
729 = arch_float_type (gdbarch
, gdbarch_double_bit (gdbarch
),
730 "real*8", gdbarch_double_format (gdbarch
));
731 auto fmt
= gdbarch_floatformat_for_type (gdbarch
, "real(kind=16)", 128);
733 builtin_f_type
->builtin_real_s16
734 = arch_float_type (gdbarch
, 128, "real*16", fmt
);
735 else if (gdbarch_long_double_bit (gdbarch
) == 128)
736 builtin_f_type
->builtin_real_s16
737 = arch_float_type (gdbarch
, gdbarch_long_double_bit (gdbarch
),
738 "real*16", gdbarch_long_double_format (gdbarch
));
740 builtin_f_type
->builtin_real_s16
741 = arch_type (gdbarch
, TYPE_CODE_ERROR
, 128, "real*16");
743 builtin_f_type
->builtin_complex_s8
744 = init_complex_type ("complex*8", builtin_f_type
->builtin_real
);
745 builtin_f_type
->builtin_complex_s16
746 = init_complex_type ("complex*16", builtin_f_type
->builtin_real_s8
);
748 if (builtin_f_type
->builtin_real_s16
->code () == TYPE_CODE_ERROR
)
749 builtin_f_type
->builtin_complex_s32
750 = arch_type (gdbarch
, TYPE_CODE_ERROR
, 256, "complex*32");
752 builtin_f_type
->builtin_complex_s32
753 = init_complex_type ("complex*32", builtin_f_type
->builtin_real_s16
);
755 return builtin_f_type
;
758 static struct gdbarch_data
*f_type_data
;
760 const struct builtin_f_type
*
761 builtin_f_type (struct gdbarch
*gdbarch
)
763 return (const struct builtin_f_type
*) gdbarch_data (gdbarch
, f_type_data
);
766 void _initialize_f_language ();
768 _initialize_f_language ()
770 f_type_data
= gdbarch_data_register_post_init (build_fortran_types
);
776 fortran_argument_convert (struct value
*value
, bool is_artificial
)
780 /* If the value is not in the inferior e.g. registers values,
781 convenience variables and user input. */
782 if (VALUE_LVAL (value
) != lval_memory
)
784 struct type
*type
= value_type (value
);
785 const int length
= TYPE_LENGTH (type
);
787 = value_as_long (value_allocate_space_in_inferior (length
));
788 write_memory (addr
, value_contents (value
), length
);
790 = value_from_contents_and_address (type
, value_contents (value
),
792 return value_addr (val
);
795 return value_addr (value
); /* Program variables, e.g. arrays. */
803 fortran_preserve_arg_pointer (struct value
*arg
, struct type
*type
)
805 if (value_type (arg
)->code () == TYPE_CODE_PTR
)
806 return value_type (arg
);