DWARF: cannot break on out-of-line function nested inside inlined function.

Consider the following code, which defines a function, Child2,
which is itself nested inside Child1:

    procedure Foo_O224_021 is
        O1 : constant Object_Type := Get_Str ("Foo");
        procedure Child1 is
            O2 : constant Object_Type := Get_Str ("Foo");
            function Child2 (S : String) return Boolean is -- STOP
            begin
                for C of S loop
                    Do_Nothing (C);
                    if C = 'o' then
                        return True;
                    end if;
                end loop;
                return False;
            end Child2;
            R : Boolean;
        begin
            R := Child2 ("Foo");
            R := Child2 ("Bar");
            R := Child2 ("Foobar");
        end Child1;
    begin
        Child1;
    end Foo_O224_021;

On x86_64-linux, when compiled at -O2, GDB is unable to insert
a breakpoint on Child2:

    % gnatmake -g -O2 foo_o224_021
    % gdb foo_o224_021
    (gdb) b child2
    Function "child2" not defined.
    (gdb) b foo_o224_021.child1.child2
    Function "foo_o224_021.child1.child2" not defined.

The problem is caused by the fact that GDB did not create a symbol
for Child2, and this, in turn, is caused by the fact that the compiler
decided to inline Child1, but not Child2. The DWARF debugging info
first provides an abstract instance tree for Child1...

 <3><1b7b>: Abbrev Number: 29 (DW_TAG_subprogram)
    <1b7c>   DW_AT_name        : (indirect string, offset: 0x23f8): foo_o224_021__child1
    <1b82>   DW_AT_inline      : 1      (inlined)
    <1b83>   DW_AT_sibling     : <0x1c01>

... where that subprogram is given the DW_AT_inline attribute.
Inside that function there is a lexical block which has no PC
range (corresponding to the fact that this is the abstract tree):

 <4><1b87>: Abbrev Number: 30 (DW_TAG_lexical_block)

... inside which our subprogram Child2 is described:

 <5><1b92>: Abbrev Number: 32 (DW_TAG_subprogram)
    <1b93>   DW_AT_name        : (indirect string, offset: 0x2452): foo_o224_021__child1__child2
    <1b99>   DW_AT_type        : <0x1ab1>
    <1b9d>   DW_AT_low_pc      : 0x402300
    <1ba5>   DW_AT_high_pc     : 0x57
    [...]

Then, later on, we get the concrete instance tree, starting at:

 <3><1c5e>: Abbrev Number: 41 (DW_TAG_inlined_subroutine)
    <1c5f>   DW_AT_abstract_origin: <0x1b7b>
    <1c63>   DW_AT_entry_pc    : 0x4025fd
    <1c6b>   DW_AT_ranges      : 0x150

... which refers to Child1. One of that inlined subroutine children
is the concrete instance of the empty lexical block we saw above
(in the abstract instance tree), which gives the actual address
range for this inlined instance:

 <5><1c7a>: Abbrev Number: 43 (DW_TAG_lexical_block)
    <1c7b>   DW_AT_abstract_origin: <0x1b87>
    <1c7f>   DW_AT_ranges      : 0x180

This is the DIE which provides the context inside which we can
record Child2. But unfortunately, GDB does not take the abstract
origin into account when handling lexical blocks, causing it
to miss the fact that this block contains some symbols described
in the abstract instance tree. This is the first half of this patch:
modifying GDB to follow DW_AT_abstract_origin attributes for
lexical blocks.

But this not enough to fix the issue, as we're still unable to
break on Child2 with just that change. The second issue can be
traced to the way inherit_abstract_dies determines the list of
DIEs to inherit from. For that, it iterates over all the DIEs in
the concrete instance tree, and finds the list of DIEs from the
abstract instance tree that are not referenced from the concrete
instance tree. As it happens, there is one type of DIE in the
concrete instance tree which does reference Child2's DIE, but
in fact does otherwise define a concrete instance of the reference
DIE; that's (where <0x1b92> is Child2's DIE):

 <6><1d3c>: Abbrev Number: 35 (DW_TAG_GNU_call_site)
    <1d3d>   DW_AT_low_pc      : 0x4026a4
    <1d45>   DW_AT_abstract_origin: <0x1b92>

So, the second part of the patch is to modify inherit_abstract_dies
to ignore DW_TAG_GNU_call_site DIEs when iterating over the concrete
instance tree.

This patch also includes a testcase which can be used to reproduce
the issue. Unfortunately, for it to actually pass, a smal patch in
GCC is also necessary to make sure that GCC provides lexical blocks'
DW_AT_abstract_origin attributes from the concrete tree back to
the abstract tree. We hope to be able to submit and integrate that
patch in the GCC tree soon. Meanwhile, a setup_xfail has been added.

gdb/ChangeLog:

	2014-05-05  Pierre-Marie de Rodat  <derodat@adacore.com>
	* dwarf2read.c (inherit_abstract_dies): Skip
	DW_TAG_GNU_call_site dies while inheriting children of an
	abstract DIE into a scope.
	(read_lexical_block_scope): Inherit abstract DIE's for
	lexical scopes.

gdb/testsuite/ChangeLog:

        * gdb.ada/out_of_line_in_inlined: New testcase.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e01b98b53704d4777c2f23783d0df4a48517aa44..b4bcef156df44f95ce61e428a3305568ec977cc3 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,11 @@
+2014-05-05  Pierre-Marie de Rodat  <derodat@adacore.com>
+
+       * dwarf2read.c (inherit_abstract_dies): Skip
+       DW_TAG_GNU_call_site dies while inheriting children of an
+       abstract DIE into a scope.
+       (read_lexical_block_scope): Inherit abstract DIE's for
+       lexical scopes.
+
 2015-05-05  Joel Brobecker  <brobecker@adacore.com>
 
        * ada-valprint.c (val_print_packed_array_elements): Delete

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index b91fbf5d34fd317b5eb5e0dc906ca730d65dcfa3..4982922157511c7a711fe70f055559cba5de9729 100644 (file)
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -11216,17 +11216,28 @@ inherit_abstract_dies (struct die_info *die, struct dwarf2_cu *cu)
   cleanups = make_cleanup (xfree, offsets);
 
   offsets_end = offsets;
-  child_die = die->child;
-  while (child_die && child_die->tag)
+  for (child_die = die->child;
+       child_die && child_die->tag;
+       child_die = sibling_die (child_die))
     {
+      struct die_info *child_origin_die;
+      struct dwarf2_cu *child_origin_cu;
+
+      /* We are trying to process concrete instance entries:
+        DW_TAG_GNU_call_site DIEs indeed have a DW_AT_abstract_origin tag, but
+        it's not relevant to our analysis here. i.e. detecting DIEs that are
+        present in the abstract instance but not referenced in the concrete
+        one.  */
+      if (child_die->tag == DW_TAG_GNU_call_site)
+       continue;
+
       /* For each CHILD_DIE, find the corresponding child of
         ORIGIN_DIE.  If there is more than one layer of
         DW_AT_abstract_origin, follow them all; there shouldn't be,
         but GCC versions at least through 4.4 generate this (GCC PR
         40573).  */
-      struct die_info *child_origin_die = child_die;
-      struct dwarf2_cu *child_origin_cu = cu;
-
+      child_origin_die = child_die;
+      child_origin_cu = cu;
       while (1)
        {
          attr = dwarf2_attr (child_origin_die, DW_AT_abstract_origin,
@@ -11256,7 +11267,6 @@ inherit_abstract_dies (struct die_info *die, struct dwarf2_cu *cu)
          else
            *offsets_end++ = child_origin_die->offset;
        }
-      child_die = sibling_die (child_die);
     }
   qsort (offsets, offsets_end - offsets, sizeof (*offsets),
         unsigned_int_compar);
@@ -11503,6 +11513,7 @@ read_lexical_block_scope (struct die_info *die, struct dwarf2_cu *cu)
          child_die = sibling_die (child_die);
        }
     }
+  inherit_abstract_dies (die, cu);
   newobj = pop_context ();
 
   if (local_symbols != NULL || using_directives != NULL)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index c0b51bed53385b008726a42d93e2d9f587a38ba0..66a87c8f6c2ac7ac33823a918d7bba0a8a101f54 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2015-05-05  Joel Brobecker  <brobecker@adacore.com>
+
+       * gdb.ada/out_of_line_in_inlined: New testcase.
+
 2015-05-05  Joel Brobecker  <brobecker@adacore.com>
 
        * gdb.ada/var_rec_arr: New testcase.

diff --git a/gdb/testsuite/gdb.ada/out_of_line_in_inlined.exp b/gdb/testsuite/gdb.ada/out_of_line_in_inlined.exp
new file mode 100644 (file)
index 0000000..ebebb6c
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/out_of_line_in_inlined.exp
@@ -0,0 +1,31 @@
+# Copyright 2015 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/>.
+
+load_lib "ada.exp"
+
+standard_ada_testfile foo_o224_021
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable {debug optimize=-O2}] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+# GCC currently is missing a DW_AT_origin attribute in one of the
+# lexical blocks, preventing GDB from creating a symbol for the
+# subprogram we want to break on.
+setup_xfail "*-*-*"
+gdb_test "break foo_o224_021.child1.child2" \
+         "Breakpoint \[0-9\]+ at.*: file .*foo_o224_021.adb, line \[0-9\]+."

diff --git a/gdb/testsuite/gdb.ada/out_of_line_in_inlined/bar.adb b/gdb/testsuite/gdb.ada/out_of_line_in_inlined/bar.adb
new file mode 100644 (file)
index 0000000..a7178cc
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/out_of_line_in_inlined/bar.adb
@@ -0,0 +1,28 @@
+--  Copyright 2015 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/>.
+
+package body Bar is
+
+    procedure Do_Nothing (C : Character) is
+    begin
+        null;
+    end Do_Nothing;
+
+    function Get_Str (S1 : String; S2 : String := "") return Object_Type is
+    begin
+        return (Ada.Finalization.Controlled with Value => True);
+    end Get_Str;
+
+end Bar;

diff --git a/gdb/testsuite/gdb.ada/out_of_line_in_inlined/bar.ads b/gdb/testsuite/gdb.ada/out_of_line_in_inlined/bar.ads
new file mode 100644 (file)
index 0000000..81a249c
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/out_of_line_in_inlined/bar.ads
@@ -0,0 +1,27 @@
+--  Copyright 2015 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/>.
+
+with Ada.Finalization;
+
+package Bar is
+
+    type Object_Type is new Ada.Finalization.Controlled with record
+        Value : Boolean;
+    end record;
+
+    function Get_Str (S1 : String; S2 : String := "") return Object_Type;
+    procedure Do_Nothing (C : Character);
+
+end Bar;

diff --git a/gdb/testsuite/gdb.ada/out_of_line_in_inlined/foo_o224_021.adb b/gdb/testsuite/gdb.ada/out_of_line_in_inlined/foo_o224_021.adb
new file mode 100644 (file)
index 0000000..15e108d
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/out_of_line_in_inlined/foo_o224_021.adb
@@ -0,0 +1,44 @@
+--  Copyright 2015 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/>.
+
+with Bar; use Bar;
+
+procedure Foo_O224_021 is
+    O1 : constant Object_Type := Get_Str ("Foo");
+
+    procedure Child1 is
+        O2 : constant Object_Type := Get_Str ("Foo");
+
+        function Child2 (S : String) return Boolean is -- STOP
+        begin
+            for C of S loop
+                Do_Nothing (C);
+                if C = 'o' then
+                    return True;
+                end if;
+            end loop;
+            return False;
+        end Child2;
+
+        R : Boolean;
+
+    begin
+        R := Child2 ("Foo");
+        R := Child2 ("Bar");
+        R := Child2 ("Foobar");
+    end Child1;
+begin
+    Child1;
+end Foo_O224_021;