[binutils-gdb] [gdb/symtab] Handle DW_AT_string_length with location list

[Tom de Vries <vries@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5b151607e1faf27238e9dce6d3124741779dcc3a

commit 5b151607e1faf27238e9dce6d3124741779dcc3a
Author: Tom de Vries <tdevries@suse.de>
Date:   Thu Oct 28 10:43:34 2021 +0200

    [gdb/symtab] Handle DW_AT_string_length with location list
    
    Consider a fortran routine where a string variable s is modified:
    ...
    subroutine f(s)
      character*(*) s
      print *, s
      s(1:3) = 'oof'
      print *, s
    end subroutine f
    ...
    
    When compiling with optimization level -O1 and printing the type of
    variable s we get:
    ...
    $ gdb -q -batch outputs/gdb.opt/fortran-string/fortran-string \
      -ex "b f" \
      -ex run \
      -ex "ptype s"
    Breakpoint 1 at 0x4006f7: file fortran-string.f90, line 21.
    
    Breakpoint 1, f (s=..., _s=_s@entry=3) at fortran-string.f90:21
    21      subroutine f(s)
    type = character*1
    ...
    while with -O0 we have instead:
    ...
    type = character (3)
    ...
    
    The problem is that the type of s is:
    ...
     <1><2d6>: Abbrev Number: 21 (DW_TAG_string_type)
        <2d7>   DW_AT_string_length: 0xbf (location list)
        <2db>   DW_AT_byte_size   : 4
    ...
    where the DW_AT_string_length is a location list, a case that is not handled
    by attr_to_dynamic_prop.
    
    Fix this by handling attr->form_is_section_offset () in attr_to_dynamic_prop.
    
    Tested on x86_64-linux.
    
    The test-case is based on gdb.opt/fortran-string.exp from
    https://src.fedoraproject.org/rpms/gdb/raw/f32/f/gdb-archer-vla-tests.patch .
    I've updated the copyrights to stretch to 2021.
    
    [ I've tried to create a dwarf assembly test-case for this, but didn't
    manage. ]
    
    Co-Authored-By: Jan Kratochvil <jan.kratochvil@redhat.com>
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=26910

Diff:
---
 gdb/dwarf2/read.c                        | 24 ++++++++++++++++----
 gdb/testsuite/gdb.opt/fortran-string.exp | 38 ++++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.opt/fortran-string.f90 | 27 +++++++++++++++++++++++
 3 files changed, 85 insertions(+), 4 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index bd0754618d0..af184d4d1fd 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -18468,14 +18468,30 @@ attr_to_dynamic_prop (const struct attribute *attr, struct die_info *die,
     }
   else if (attr->form_is_constant ())
     prop->set_const_val (attr->constant_value (0));
-  else
+  else if (attr->form_is_section_offset ())
     {
-      dwarf2_invalid_attrib_class_complaint (dwarf_form_name (attr->form),
-					     dwarf2_name (die, cu));
-      return 0;
+      switch (attr->name)
+	{
+	case DW_AT_string_length:
+	  baton = XOBNEW (obstack, struct dwarf2_property_baton);
+	  baton->property_type = default_type;
+	  fill_in_loclist_baton (cu, &baton->loclist, attr);
+	  prop->set_loclist (baton);
+	  gdb_assert (prop->baton () != NULL);
+	  break;
+	default:
+	  goto invalid;
+	}
     }
+  else
+    goto invalid;
 
   return 1;
+
+ invalid:
+  dwarf2_invalid_attrib_class_complaint (dwarf_form_name (attr->form),
+					 dwarf2_name (die, cu));
+  return 0;
 }
 
 /* See read.h.  */
diff --git a/gdb/testsuite/gdb.opt/fortran-string.exp b/gdb/testsuite/gdb.opt/fortran-string.exp
new file mode 100644
index 00000000000..9bf6269f840
--- /dev/null
+++ b/gdb/testsuite/gdb.opt/fortran-string.exp
@@ -0,0 +1,38 @@
+# Copyright 2009-2021 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/> .
+
+# Test GDB can cope with Fortran strings having their length present in a CPU
+# register.  With -O0 the string length is passed on the stack.  To make this
+# test meaningful the follow assertion should pass.  It is not being checked
+# here as the "_s" symbol is compiler dependent:
+#   (gdb) info address _s
+#   Symbol "_s" is a variable in register XX.
+
+standard_testfile .f90
+
+if { [prepare_for_testing "prepare for testing" ${testfile} ${srcfile} \
+	  {debug f90 additional_flags=-O1}] } {
+    return -1
+}
+
+if ![runto f] then {
+    perror "couldn't run to f"
+    continue
+}
+
+gdb_test_no_output "set print frame-arguments all"
+gdb_test "frame" ".*s='foo'.*"
+gdb_test "ptype s" "type = character \\(3\\)"
+gdb_test "p s" "\\$\[0-9\]* = 'foo'"
diff --git a/gdb/testsuite/gdb.opt/fortran-string.f90 b/gdb/testsuite/gdb.opt/fortran-string.f90
new file mode 100644
index 00000000000..71b6baea05a
--- /dev/null
+++ b/gdb/testsuite/gdb.opt/fortran-string.f90
@@ -0,0 +1,27 @@
+! Copyright 2009-2021 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/>.
+
+subroutine f(s)
+  character*(*) s
+  print *, s
+  s(1:3) = 'oof'
+  print *, s
+end subroutine f
+
+program main
+  character*3 s;
+  s = 'foo'
+  call f (s)
+end program main