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.

3 files changed, 350 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 8805fd9..5f2100b 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -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
diff --git a/gdb/testsuite/gdb.fortran/function-calls.exp b/gdb/testsuite/gdb.fortran/function-calls.exp
new file mode 100644
index 0000000..9db889a
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/function-calls.exp
@@ -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"
diff --git a/gdb/testsuite/gdb.fortran/function-calls.f90 b/gdb/testsuite/gdb.fortran/function-calls.f90
new file mode 100644
index 0000000..d7bcd71
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/function-calls.f90
@@ -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