gdb, testsuite, fortran: Fix sizeof intrinsic for Fortran pointers

For Fortran pointers gfortran/ifx emits DW_TAG_pointer_types like

<2><17d>: Abbrev Number: 22 (DW_TAG_variable)
   <180>   DW_AT_name        : (indirect string, offset: 0x1f1): fptr
   <184>   DW_AT_type        : <0x214>
...
<1><219>: Abbrev Number: 27 (DW_TAG_array_type)
   <21a>   DW_AT_type        : <0x10e>
   <216>   DW_AT_associated  : ...

The 'pointer property' in Fortran is implicitly modeled by adding a
DW_AT_associated to the type of the variable (see also the
DW_AT_associated description in DWARF 5).  A Fortran pointer is more
than an address and thus different from a C pointer.  It is a
self contained type having additional fields such as, e.g., the rank of
its underlying array.  This motivates the intended DWARF modeling of
Fortran pointers via the DW_AT_associated attribute.

This patch adds support for the sizeof intrinsic by simply dereferencing
pointer types when encountered during a sizeof evaluation.

The patch also adds a test for the sizeof intrinsic which was not tested
before.

Tested-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Approved-By: Tom Tromey <tom@tromey.com>

2 files changed, 223 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.fortran/sizeof.exp b/gdb/testsuite/gdb.fortran/sizeof.exp
new file mode 100644
index 0000000..be59a37
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/sizeof.exp
@@ -0,0 +1,115 @@
+# Copyright 2024 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/> .
+
+# Testing GDB's implementation of SIZE keyword.
+
+require allow_fortran_tests
+
+standard_testfile ".f90"
+load_lib fortran.exp
+
+if {[prepare_for_testing ${testfile}.exp ${testfile} ${srcfile} \
+    {debug f90}]} {
+    return -1
+}
+
+if ![fortran_runto_main] {
+    return -1
+}
+
+gdb_breakpoint [gdb_get_line_number "Test breakpoint"]
+gdb_breakpoint [gdb_get_line_number "Past unassigned pointers"]
+gdb_breakpoint [gdb_get_line_number "Final breakpoint"]
+
+set done_unassigned 0
+set found_final_breakpoint 0
+set test_count 0
+
+# We are running tests defined in the executable here.  So, in the .exp file
+# we do not know when the 'Final breakpoint' will be hit exactly.  We place a
+# limit on the number of tests that can be run, just in case something goes
+# wrong, and GDB gets stuck in an loop here.
+while { $test_count < 200 } {
+    with_test_prefix "test $test_count" {
+	incr test_count
+
+	gdb_test_multiple "continue" "continue" {
+	    -re -wrap "! Test breakpoint" {
+		# We can run a test from here.
+	    }
+	    -re -wrap "! Past unassigned pointers" {
+		# Done with testing unassigned pointers.
+		set done_unassigned 1
+		continue
+	    }
+	    -re -wrap "! Final breakpoint" {
+		# We're done with the tests.
+		set found_final_breakpoint 1
+	    }
+	}
+
+	if ($found_final_breakpoint) {
+	    break
+	}
+
+	# First grab the expected answer.
+	set answer [get_valueof "" "answer" "**unknown**"]
+
+	# Now move up a frame and figure out a command for us to run
+	# as a test.
+	set command ""
+	gdb_test_multiple "up" "up" {
+	    -re -wrap "\r\n\[0-9\]+\[ \t\]+call test_sizeof \\((\[^\r\n\]+)\\)" {
+		set command $expect_out(1,string)
+	    }
+	}
+
+	gdb_assert { ![string equal $command ""] } "found a command to run"
+
+	set is_pointer_to_array [string match "sizeof (*a_p)*" $command]
+
+	if {$done_unassigned || !$is_pointer_to_array} {
+	    gdb_test "p $command" " = $answer"
+	} else {
+	    # Gfortran and ifx have slightly different behavior for unassigned
+	    # pointers to arrays.  While ifx will print 0 as the sizeof result,
+	    # gfortran will print the size of the base type of the pointer or
+	    # array.  Since the default behavior in GDB was to print 0 we keep
+	    # this and make an exception for gfortran here.
+	    gdb_test_multiple "p $command" "p $command" {
+		-re -wrap " = $answer" {
+		    pass $gdb_test_name
+		}
+		-re -wrap " = 0" {
+		    pass $gdb_test_name
+		}
+	    }
+	}
+    }
+}
+
+gdb_assert {$found_final_breakpoint} "ran all compiled in tests"
+
+# Here some more GDB specific tests that might fail with compilers.
+# GDB will print sizeof(1.4) = 8 while gfortran will probably print 4 but
+# GDB says ptype 1.4 is real*8 so the output is expected.
+
+gdb_test "ptype 1" "type = int"
+gdb_test "p sizeof(1)" "= 4"
+
+gdb_test "ptype 1.3" "type = real\\*8"
+gdb_test "p sizeof(1.3)" "= 8"
+
+gdb_test  "p sizeof ('asdsasd')" "= 7"
diff --git a/gdb/testsuite/gdb.fortran/sizeof.f90 b/gdb/testsuite/gdb.fortran/sizeof.f90
new file mode 100644
index 0000000..b8490a1
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/sizeof.f90
@@ -0,0 +1,108 @@
+! Copyright 2024 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/>.
+
+module data
+  use, intrinsic :: iso_c_binding, only : C_SIZE_T
+  implicit none
+
+  character, target :: char_v
+  character (len=3), target :: char_a
+  integer, target :: int_v
+  integer, target, dimension(:,:) :: int_2da (3,2)
+  real*4, target :: real_v
+  real*4, target :: real_a(4)
+  real*4, target, dimension (:), allocatable :: real_a_alloc
+
+  character, pointer :: char_v_p
+  character (len=3), pointer :: char_a_p
+  integer, pointer :: int_v_p
+  integer, pointer, dimension (:,:) :: int_2da_p
+  real*4, pointer :: real_v_p
+  real*4, pointer, dimension(:) :: real_a_p
+  real*4, dimension(:), pointer :: real_alloc_a_p
+
+contains
+subroutine test_sizeof (answer)
+  integer(C_SIZE_T) :: answer
+
+  print *, answer ! Test breakpoint
+end subroutine test_sizeof
+
+subroutine run_tests ()
+  call test_sizeof (sizeof (char_v))
+  call test_sizeof (sizeof (char_a))
+  call test_sizeof (sizeof (int_v))
+  call test_sizeof (sizeof (int_2da))
+  call test_sizeof (sizeof (real_v))
+  call test_sizeof (sizeof (real_a))
+  call test_sizeof (sizeof (real_a_alloc))
+
+  call test_sizeof (sizeof (char_v_p))
+  call test_sizeof (sizeof (char_a_p))
+  call test_sizeof (sizeof (int_v_p))
+  call test_sizeof (sizeof (int_2da_p))
+  call test_sizeof (sizeof (real_v_p))
+  call test_sizeof (sizeof (real_a_p))
+  call test_sizeof (sizeof (real_alloc_a_p))
+end subroutine run_tests
+
+end module data
+
+program sizeof_tests
+  use iso_c_binding
+  use data
+
+  implicit none
+
+  allocate (real_a_alloc(5))
+
+  nullify (char_v_p)
+  nullify (char_a_p)
+  nullify (int_v_p)
+  nullify (int_2da_p)
+  nullify (real_v_p)
+  nullify (real_a_p)
+  nullify (real_alloc_a_p)
+
+  ! Test nullified
+  call run_tests ()
+
+  char_v_p => char_v ! Past unassigned pointers
+  char_a_p => char_a
+  int_v_p => int_v
+  int_2da_p => int_2da
+  real_v_p => real_v
+  real_a_p => real_a
+  real_alloc_a_p => real_a_alloc
+
+  ! Test pointer assignment
+  call run_tests ()
+
+  char_v = 'a'
+  char_a = "aaa"
+  int_v = 10
+  int_2da = reshape((/1, 2, 3, 4, 5, 6/), shape(int_2da))
+  real_v = 123.123
+  real_a_p = (/-1.1, -1.2, -1.3, -1.4/)
+  real_a_alloc = (/1.1, 2.2, 3.3, 4.4, 5.5/)
+
+  ! After allocate/value assignment
+  call run_tests ()
+
+  deallocate (real_a_alloc)
+
+  print *, "done" ! Final breakpoint
+
+end program sizeof_tests