Fortran function calls with arguments

Prior to this patch, calling functions on the inferior with arguments and
then using these arguments within a function resulted in an invalid
memory access. This is because Fortran arguments are typically passed as
pointers to values.

It is possible to call Fortran functions, but memory must be allocated in
the inferior, so a pointer can be passed to the function, and the
language must be set to C to enable C-style casting. This is cumbersome
and not a pleasant debug experience.

This patch implements the GNU Fortran argument passing conventions with
caveats. Firstly, it does not handle the VALUE attribute as there is
insufficient DWARF information to determine when this is the case.
Secondly, functions with optional parameters can only be called with all
parameters present. Both these cases are marked as KFAILS in the test.

Since the GNU Fortran argument passing convention has been implemented,
there is no guarantee that this patch will work correctly, in all cases,
with other compilers.

Despite these limitations, this patch improves the ease with which
functions can be called in many cases, without taking away the existing
approach of calling with the language set to C.

Regression tested on x86_64, aarch64 and POWER9 with GCC 7.3.0.
Regression tested with Ada on x86_64.
Regression tested with native-extended-gdbserver target board.

gdb/ChangeLog:

	* eval.c (evaluate_subexp_standard): Call Fortran argument
	wrapping logic.
	* f-lang.c (struct value): A value which can be passed into a
	Fortran function call.
	(fortran_argument_convert): Wrap Fortran arguments in a pointer
	where appropriate.
	(struct type): Value ready for a Fortran function call.
	(fortran_preserve_arg_pointer): Undo check_typedef, the pointer
	is needed.
	* f-lang.h (fortran_argument_convert): Declaration.
	(fortran_preserve_arg_pointer): Declaration.
	* infcall.c (value_arg_coerce): Call Fortran argument logic.

gdb/testsuite/ChangeLog:

	* gdb.fortran/function-calls.exp: New file.
	* gdb.fortran/function-calls.f90: New test.
This commit is contained in:
Richard Bunt 2019-03-06 08:23:00 +00:00
parent 2d0d5fc6f0
commit aa3cfbda2f
8 changed files with 457 additions and 3 deletions

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@ -1,3 +1,20 @@
2019-03-06 Richard Bunt <richard.bunt@arm.com>
Dirk Schubert <dirk.schubert@arm.com>
Chris January <chris.january@arm.com>
* eval.c (evaluate_subexp_standard): Call Fortran argument
wrapping logic.
* f-lang.c (struct value): A value which can be passed into a
Fortran function call.
(fortran_argument_convert): Wrap Fortran arguments in a pointer
where appropriate.
(struct type): Value ready for a Fortran function call.
(fortran_preserve_arg_pointer): Undo check_typedef, the pointer
is needed.
* f-lang.h (fortran_argument_convert): Declaration.
(fortran_preserve_arg_pointer): Declaration.
* infcall.c (value_arg_coerce): Call Fortran argument logic.
2019-03-05 Tom Tromey <tromey@adacore.com>
* python/py-prettyprint.c (print_string_repr): Remove #if.

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@ -1987,7 +1987,20 @@ evaluate_subexp_standard (struct type *expect_type,
argvec[0] = arg1;
tem = 1;
for (; tem <= nargs; tem++)
argvec[tem] = evaluate_subexp_with_coercion (exp, pos, noside);
{
argvec[tem] = evaluate_subexp_with_coercion (exp, pos, noside);
/* Arguments in Fortran are passed by address. Coerce the
arguments here rather than in value_arg_coerce as otherwise
the call to malloc to place the non-lvalue parameters in
target memory is hit by this Fortran specific logic. This
results in malloc being called with a pointer to an integer
followed by an attempt to malloc the arguments to malloc in
target memory. Infinite recursion ensues. */
bool is_artificial =
TYPE_FIELD_ARTIFICIAL (value_type (arg1), tem - 1);
argvec[tem] = fortran_argument_convert (argvec[tem],
is_artificial);
}
argvec[tem] = 0; /* signal end of arglist */
if (noside == EVAL_SKIP)
return eval_skip_value (exp);

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@ -27,6 +27,7 @@
#include "parser-defs.h"
#include "language.h"
#include "varobj.h"
#include "gdbcore.h"
#include "f-lang.h"
#include "valprint.h"
#include "value.h"
@ -371,3 +372,40 @@ _initialize_f_language (void)
{
f_type_data = gdbarch_data_register_post_init (build_fortran_types);
}
/* See f-lang.h. */
struct value *
fortran_argument_convert (struct value *value, bool is_artificial)
{
if (!is_artificial)
{
/* If the value is not in the inferior e.g. registers values,
convenience variables and user input. */
if (VALUE_LVAL (value) != lval_memory)
{
struct type *type = value_type (value);
const int length = TYPE_LENGTH (type);
const CORE_ADDR addr
= value_as_long (value_allocate_space_in_inferior (length));
write_memory (addr, value_contents (value), length);
struct value *val
= value_from_contents_and_address (type, value_contents (value),
addr);
return value_addr (val);
}
else
return value_addr (value); /* Program variables, e.g. arrays. */
}
return value;
}
/* See f-lang.h. */
struct type *
fortran_preserve_arg_pointer (struct value *arg, struct type *type)
{
if (TYPE_CODE (value_type (arg)) == TYPE_CODE_PTR)
return value_type (arg);
return type;
}

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@ -82,4 +82,37 @@ struct builtin_f_type
/* Return the Fortran type table for the specified architecture. */
extern const struct builtin_f_type *builtin_f_type (struct gdbarch *gdbarch);
/* Ensures that function argument VALUE is in the appropriate form to
pass to a Fortran function. Returns a possibly new value that should
be used instead of VALUE.
When IS_ARTIFICIAL is true this indicates an artificial argument,
e.g. hidden string lengths which the GNU Fortran argument passing
convention specifies as being passed by value.
When IS_ARTIFICIAL is false, the argument is passed by pointer. If the
value is already in target memory then return a value that is a pointer
to VALUE. If VALUE is not in memory (e.g. an integer literal), allocate
space in the target, copy VALUE in, and return a pointer to the in
memory copy. */
extern struct value *fortran_argument_convert (struct value *value,
bool is_artificial);
/* Ensures that function argument TYPE is appropriate to inform the debugger
that ARG should be passed as a pointer. Returns the potentially updated
argument type.
If ARG is of type pointer then the type of ARG is returned, otherwise
TYPE is returned untouched.
This function exists to augment the types of Fortran function call
parameters to be pointers to the reported value, when the corresponding ARG
has also been wrapped in a pointer (by fortran_argument_convert). This
informs the debugger that these arguments should be passed as a pointer
rather than as the pointed to type. */
extern struct type *fortran_preserve_arg_pointer (struct value *arg,
struct type *type);
#endif /* F_LANG_H */

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@ -33,6 +33,7 @@
#include "command.h"
#include "dummy-frame.h"
#include "ada-lang.h"
#include "f-lang.h"
#include "gdbthread.h"
#include "event-top.h"
#include "observable.h"
@ -130,7 +131,7 @@ show_unwind_on_terminating_exception_p (struct ui_file *file, int from_tty,
}
/* Perform the standard coercions that are specified
for arguments to be passed to C or Ada functions.
for arguments to be passed to C, Ada or Fortran functions.
If PARAM_TYPE is non-NULL, it is the expected parameter type.
IS_PROTOTYPED is non-zero if the function declaration is prototyped.
@ -146,9 +147,11 @@ value_arg_coerce (struct gdbarch *gdbarch, struct value *arg,
struct type *type
= param_type ? check_typedef (param_type) : arg_type;
/* Perform any Ada-specific coercion first. */
/* Perform any Ada- and Fortran-specific coercion first. */
if (current_language->la_language == language_ada)
arg = ada_convert_actual (arg, type);
else if (current_language->la_language == language_fortran)
type = fortran_preserve_arg_pointer (arg, type);
/* Force the value to the target if we will need its address. At
this point, we could allocate arguments on the stack instead of

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@ -1,3 +1,8 @@
2019-03-06 Richard Bunt <richard.bunt@arm.com>
* gdb.fortran/function-calls.exp: New file.
* gdb.fortran/function-calls.f90: New test.
2019-03-04 Richard Bunt <richard.bunt@arm.com>
* gdb.fortran/short-circuit-argument-list.exp: Remove reliance

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@ -0,0 +1,103 @@
# Copyright 2019 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/> .
# Exercise passing and returning arguments in Fortran. This test case
# is based on the GNU Fortran Argument passing conventions.
if {[skip_fortran_tests]} { return -1 }
standard_testfile ".f90"
if {[prepare_for_testing ${testfile}.exp ${testfile} ${srcfile} {debug f90}]} {
return -1
}
if {![runto [gdb_get_line_number "post_init"]]} then {
perror "couldn't run to breakpoint post_init"
continue
}
# Use inspired by gdb.base/callfuncs.exp.
gdb_test_no_output "set unwindonsignal on"
# Baseline: function and subroutine call with no arguments.
gdb_test "p no_arg()" " = .TRUE."
gdb_test_no_output "call no_arg_subroutine()"
# Argument class: literal, inferior variable, convenience variable,
# function call return value, function.
# Paragraph 3: Variables are passed by reference.
gdb_test "p one_arg(.TRUE.)" " = .TRUE."
gdb_test "p one_arg(untrue)" " = .FALSE."
gdb_test_no_output "set \$var = .FALSE."
gdb_test "p one_arg(\$var)" " = .FALSE."
gdb_test "p one_arg(one_arg(.TRUE.))" " = .TRUE."
gdb_test "p one_arg(one_arg(.FALSE.))" " = .FALSE."
gdb_test_no_output "call run(no_arg_subroutine)"
# Return: constant.
gdb_test "p return_constant()" " = 17"
# Return derived type and call a function in a module.
gdb_test "p derived_types_and_module_calls::build_cart(7,8)" \
" = \\\( x = 7, y = 8 \\\)"
# Two hidden arguments. 1. returned string and 2. string length.
# Paragraph 1.
gdb_test "p return_string(returned_string_debugger, 40)" ""
gdb_test "p returned_string_debugger" "'returned in hidden first argument '"
# Argument type: real(kind=4), complex, array, pointer, derived type,
# derived type with allocatable, nested derived type.
# Paragraph 4: pointer.
gdb_test "p pointer_function(int_pointer)" " = 87"
# Paragraph 4: array.
gdb_test "call array_function(integer_array)" " = 17"
gdb_test "p derived_types_and_module_calls::pass_cart(c)" \
" = \\\( x = 2, y = 4 \\\)"
# Allocatable elements in a derived type. Technical report ISO/IEC 15581.
gdb_test "p derived_types_and_module_calls::pass_cart_nd(c_nd)" " = 4"
gdb_test "p derived_types_and_module_calls::pass_nested_cart(nested_c)" \
"= \\\( d = \\\( x = 1, y = 2 \\\), z = 3 \\\)"
# Result within some tolerance.
gdb_test "p real4_argument(real4)" " = 3.${decimal}"
# Paragraph 2. Complex argument and return.
gdb_test "p complex_argument(fft)" " = \\\(2.${decimal},3.${decimal}\\\)"
# Function with optional arguments.
# Paragraph 10: Option reference arguments.
gdb_test "p sum_some(1,2,3)" " = 6"
# There is currently no mechanism to call a function without all
# optional parameters present.
setup_kfail "gdb/24147" *-*-*
gdb_test "p sum_some(1,2)" " = 3"
# Paragraph 10: optional value arguments. There is insufficient DWARF
# information to reliably make this case work.
setup_kfail "gdb/24305" *-*-*
gdb_test "p one_arg_value(10)" " = 10"
# DW_AT_artificial formal parameters must be passed manually. This
# assert will fail if the length of the string is wrapped in a pointer.
# Paragraph 7: Character type.
gdb_test "p hidden_string_length('arbitrary string', 16)" " = 16"
# Several arguments.
gdb_test "p several_arguments(2, 3, 5)" " = 10"
gdb_test "p mix_of_scalar_arguments(5, .TRUE., 3.5)" " = 9"
# Calling other functions: Recursive call.
gdb_test "p fibonacci(6)" " = 8"

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@ -0,0 +1,242 @@
! Copyright 2019 Free Software Foundation, Inc.
!
! This program is free software; you can redistribute it and/or modify
! it under the terms of the GNU General Public License as published by
! the Free Software Foundation; either version 3 of the License, or
! (at your option) any later version.
!
! This program is distributed in the hope that it will be useful,
! but WITHOUT ANY WARRANTY; without even the implied warranty of
! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
! GNU General Public License for more details.
!
! You should have received a copy of the GNU General Public License
! along with this program. If not, see <http://www.gnu.org/licenses/> .
! Source code for function-calls.exp.
subroutine no_arg_subroutine()
end subroutine
logical function no_arg()
no_arg = .TRUE.
end function
subroutine run(a)
external :: a
call a()
end subroutine
logical function one_arg(x)
logical, intent(in) :: x
one_arg = x
end function
integer(kind=4) function one_arg_value(x)
integer(kind=4), value :: x
one_arg_value = x
end function
integer(kind=4) function several_arguments(a, b, c)
integer(kind=4), intent(in) :: a
integer(kind=4), intent(in) :: b
integer(kind=4), intent(in) :: c
several_arguments = a + b + c
end function
integer(kind=4) function mix_of_scalar_arguments(a, b, c)
integer(kind=4), intent(in) :: a
logical(kind=4), intent(in) :: b
real(kind=8), intent(in) :: c
mix_of_scalar_arguments = a + floor(c)
if (b) then
mix_of_scalar_arguments=mix_of_scalar_arguments+1
end if
end function
real(kind=4) function real4_argument(a)
real(kind=4), intent(in) :: a
real4_argument = a
end function
integer(kind=4) function return_constant()
return_constant = 17
end function
character(40) function return_string()
return_string='returned in hidden first argument'
end function
recursive function fibonacci(n) result(item)
integer(kind=4) :: item
integer(kind=4), intent(in) :: n
select case (n)
case (0:1)
item = n
case default
item = fibonacci(n-1) + fibonacci(n-2)
end select
end function
complex function complex_argument(a)
complex, intent(in) :: a
complex_argument = a
end function
integer(kind=4) function array_function(a)
integer(kind=4), dimension(11) :: a
array_function = a(ubound(a, 1, 4))
end function
integer(kind=4) function pointer_function(int_pointer)
integer, pointer :: int_pointer
pointer_function = int_pointer
end function
integer(kind=4) function hidden_string_length(string)
character*(*) :: string
hidden_string_length = len(string)
end function
integer(kind=4) function sum_some(a, b, c)
integer :: a, b
integer, optional :: c
sum_some = a + b
if (present(c)) then
sum_some = sum_some + c
end if
end function
module derived_types_and_module_calls
type cart
integer :: x
integer :: y
end type
type cart_nd
integer :: x
integer, allocatable :: d(:)
end type
type nested_cart_3d
type(cart) :: d
integer :: z
end type
contains
type(cart) function pass_cart(c)
type(cart) :: c
pass_cart = c
end function
integer(kind=4) function pass_cart_nd(c)
type(cart_nd) :: c
pass_cart_nd = ubound(c%d,1,4)
end function
type(nested_cart_3d) function pass_nested_cart(c)
type(nested_cart_3d) :: c
pass_nested_cart = c
end function
type(cart) function build_cart(x,y)
integer :: x, y
build_cart%x = x
build_cart%y = y
end function
end module
program function_calls
use derived_types_and_module_calls
implicit none
interface
logical function no_arg()
end function
logical function one_arg(x)
logical, intent(in) :: x
end function
integer(kind=4) function pointer_function(int_pointer)
integer, pointer :: int_pointer
end function
integer(kind=4) function several_arguments(a, b, c)
integer(kind=4), intent(in) :: a
integer(kind=4), intent(in) :: b
integer(kind=4), intent(in) :: c
end function
complex function complex_argument(a)
complex, intent(in) :: a
end function
real(kind=4) function real4_argument(a)
real(kind=4), intent(in) :: a
end function
integer(kind=4) function return_constant()
end function
character(40) function return_string()
end function
integer(kind=4) function one_arg_value(x)
integer(kind=4), value :: x
end function
integer(kind=4) function sum_some(a, b, c)
integer :: a, b
integer, optional :: c
end function
integer(kind=4) function mix_of_scalar_arguments(a, b, c)
integer(kind=4), intent(in) :: a
logical(kind=4), intent(in) :: b
real(kind=8), intent(in) :: c
end function
integer(kind=4) function array_function(a)
integer(kind=4), dimension(11) :: a
end function
integer(kind=4) function hidden_string_length(string)
character*(*) :: string
end function
end interface
logical :: untrue, no_arg_return
complex :: fft, fft_result
integer(kind=4), dimension (11) :: integer_array
real(kind=8) :: real8
real(kind=4) :: real4
integer, pointer :: int_pointer
integer, target :: pointee, several_arguments_return
integer(kind=4) :: integer_return
type(cart) :: c, cout
type(cart_nd) :: c_nd
type(nested_cart_3d) :: nested_c
character(40) :: returned_string, returned_string_debugger
real8 = 3.00
real4 = 9.3
integer_array = 17
fft = cmplx(2.1, 3.3)
print *, fft
untrue = .FALSE.
int_pointer => pointee
pointee = 87
c%x = 2
c%y = 4
c_nd%x = 4
allocate(c_nd%d(4))
c_nd%d = 6
nested_c%z = 3
nested_c%d%x = 1
nested_c%d%y = 2
! Use everything so it is not elided by the compiler.
call no_arg_subroutine()
no_arg_return = no_arg() .AND. one_arg(.FALSE.)
several_arguments_return = several_arguments(1,2,3) + return_constant()
integer_return = array_function(integer_array)
integer_return = mix_of_scalar_arguments(2, untrue, real8)
real4 = real4_argument(3.4)
integer_return = pointer_function(int_pointer)
c = pass_cart(c)
integer_return = pass_cart_nd(c_nd)
nested_c = pass_nested_cart(nested_c)
integer_return = hidden_string_length('string of implicit length')
call run(no_arg_subroutine)
integer_return = one_arg_value(10)
integer_return = sum_some(1,2,3)
returned_string = return_string()
cout = build_cart(4,5)
fft_result = complex_argument(fft)
print *, cout
print *, several_arguments_return
print *, fft_result
print *, real4
print *, integer_return
print *, returned_string_debugger
deallocate(c_nd%d) ! post_init
end program