Re: [PATCH] Differentiate empty vs. opaque types

[Jan Kratochvil <jan.kratochvil@redhat.com>]

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On Mon, 12 Mar 2007 04:35:29 +0100, Daniel Jacobowitz wrote:
> On Sun, Mar 11, 2007 at 11:55:19PM +0100, Jan Kratochvil wrote:
> > attached testcase targets the difference of `struct x;' vs. `struct {} x;' by checking
> > the DWARF flag `DW_AT_declaration':
...
> Does this happen in HEAD?

Yes.


> It sounds just like the problem Joel fixed
> for Ada:
> 
> 2007-01-05  Joel Brobecker  <brobecker@adacore.com>
> 
>         * dwarf2read.c (partial_die_info): Add field has_byte_size.
>         (add_partial_symbol): Correct identification of external
>         references.
>         (process_structure_scope): Likewise.
>         (read_partial_die): Handle DW_AT_byte_size attribute.
> 
> There's an Ada testcase for this, and it passes now.

I was not aware of it, I checked it now, it looks really related.

But that patch / testcase is orthogonal to my patch / testcase below.
Joel's patch targets DWARF->symbols phase while my patch targets symbols found
in different object files (executable vs. shared library).

...
> An objfile flag is usually not right - this is per-compilation-unit,
> not per objfile.

You are right. Updated, as there is no compilation-unit info reachable from
`struct type *' I had to use a new flag in each type there.


Regards,
Jan

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2007-03-12  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdbtypes.h (TYPE_FLAG_STUB_SUPPORTED, TYPE_STUB_SUPPORTED): New
	macros.
	(TYPE_IS_OPAQUE): Empty vs. opaque structures are now
	distinct on the TYPE_STUB_SUPPORTED debug targets.
	* dwarf2read.c (read_structure_type): Set TYPE_FLAG_STUB_SUPPORTED.
	* dwarfread.c (struct_type): New comment on TYPE_FLAG_STUB_SUPPORTED.

2007-03-12  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.base/type-opaque-lib.c, gdb.base/type-opaque-main.c,
	gdb.base/type-opaque.exp: New files.


--- gdb/dwarf2read.c	12 Feb 2007 15:19:31 -0000	1.215
+++ gdb/dwarf2read.c	12 Mar 2007 21:33:06 -0000
@@ -3879,6 +3879,7 @@ read_structure_type (struct die_info *di
       TYPE_LENGTH (type) = 0;
     }
 
+  TYPE_FLAGS (type) |= TYPE_FLAG_STUB_SUPPORTED;
   if (die_is_declaration (die, cu))
     TYPE_FLAGS (type) |= TYPE_FLAG_STUB;
 
--- gdb/dwarfread.c	12 Feb 2007 15:19:31 -0000	1.47
+++ gdb/dwarfread.c	12 Mar 2007 21:33:07 -0000
@@ -1083,7 +1083,10 @@ struct_type (struct dieinfo *dip, char *
      not even have any fields, if this DIE was generated due to a reference
      to an anonymous structure or union.  In this case, TYPE_FLAG_STUB is
      set, which clues gdb in to the fact that it needs to search elsewhere
-     for the full structure definition. */
+     for the full structure definition.
+     As such opaque reference is not distinguishable from an empty STRUCT
+     definition as DWARF1 is missing DW_AT_declaration we cannot set
+     TYPE_FLAG_STUB_SUPPORTED here.  */
   if (nfields == 0)
     {
       TYPE_FLAGS (type) |= TYPE_FLAG_STUB;
--- gdb/gdbtypes.h	29 Jan 2007 17:31:06 -0000	1.68
+++ gdb/gdbtypes.h	12 Mar 2007 21:33:08 -0000
@@ -319,6 +319,14 @@ enum type_code
 
 #define TYPE_FLAG_FIXED_INSTANCE (1 << 15)
 
+/* This debug target supports TYPE_STUB(t).  In the unsupported case we have to
+   rely on NFIELDS to be zero etc., see TYPE_IS_OPAQUE ().
+   TYPE_STUB(t) with !TYPE_STUB_SUPPORTED(t) may exist if we only guessed
+   the TYPE_STUB(t) value (see dwarfread.c).  */
+
+#define TYPE_FLAG_STUB_SUPPORTED (1 << 16)
+#define TYPE_STUB_SUPPORTED(t)   (TYPE_FLAGS (t) & TYPE_FLAG_STUB_SUPPORTED)
+
 /*  Array bound type.  */
 enum array_bound_type
 {
@@ -969,7 +977,8 @@ extern void allocate_cplus_struct_type (
 #define TYPE_IS_OPAQUE(thistype) (((TYPE_CODE (thistype) == TYPE_CODE_STRUCT) ||        \
                                    (TYPE_CODE (thistype) == TYPE_CODE_UNION))        && \
                                   (TYPE_NFIELDS (thistype) == 0)                     && \
-                                  (TYPE_CPLUS_SPECIFIC (thistype) && (TYPE_NFN_FIELDS (thistype) == 0)))
+                                  (TYPE_CPLUS_SPECIFIC (thistype) && (TYPE_NFN_FIELDS (thistype) == 0)) && \
+                                  (TYPE_STUB (thistype) || !TYPE_STUB_SUPPORTED (thistype)))
 
 struct builtin_type
 {
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.base/type-opaque-lib.c	12 Mar 2007 21:33:09 -0000
@@ -0,0 +1,56 @@
+/* Test resolving of an opaque type from the loaded shared library.
+
+   Copyright 2007, Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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 2 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, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+struct struct_libtype_opaque
+{ 
+  int libfield_opaque;
+};
+struct struct_libtype_opaque struct_libtype_opaque_use;
+
+struct struct_libtype_empty
+{ 
+  int libfield_empty;
+};
+struct struct_libtype_empty struct_libtype_empty_use;
+
+struct struct_libtype_filled
+{ 
+  int libfield_filled;
+};
+struct struct_libtype_filled struct_libtype_filled_use;
+
+union union_libtype_opaque
+{ 
+  int libfield_opaque;
+};
+union union_libtype_opaque union_libtype_opaque_use;
+
+union union_libtype_empty
+{ 
+  int libfield_empty;
+};
+union union_libtype_empty union_libtype_empty_use;
+
+union union_libtype_filled
+{ 
+  int libfield_filled;
+};
+union union_libtype_filled union_libtype_filled_use;
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.base/type-opaque-main.c	12 Mar 2007 21:33:09 -0000
@@ -0,0 +1,56 @@
+/* Test resolving of an opaque type from the loaded shared library.
+
+   Copyright 2007, Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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 2 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, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+struct struct_libtype_opaque;
+
+struct struct_libtype_empty
+  {
+  };    
+
+struct struct_libtype_filled
+  {
+    long mainfield_filled;
+  };    
+
+union union_libtype_opaque;
+
+union union_libtype_empty
+  {
+  };    
+
+union union_libtype_filled
+  {
+    long mainfield_filled;
+  };    
+
+int main (void)
+{
+  volatile struct struct_libtype_opaque *pointer_struct_opaque = (void *) 0;
+  volatile struct struct_libtype_empty *pointer_struct_empty = (void *) 0;
+  volatile struct struct_libtype_filled *pointer_struct_filled = (void *) 0;
+  volatile union union_libtype_opaque *pointer_union_opaque = (void *) 0;
+  volatile union union_libtype_empty *pointer_union_empty = (void *) 0;
+  volatile union union_libtype_filled *pointer_union_filled = (void *) 0;
+
+  return (int) pointer_struct_opaque + (int) pointer_struct_empty
+	 + (int) pointer_struct_filled + (int) pointer_union_opaque
+	 + (int) pointer_union_empty + (int) pointer_union_filled;
+}
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.base/type-opaque.exp	12 Mar 2007 21:33:09 -0000
@@ -0,0 +1,134 @@
+# Copyright 2004, 2007 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 2 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+# Please email any bugs, comments, and/or additions to this file to:
+# bug-gdb@prep.ai.mit.edu
+
+# Test resolving of an opaque type from the loaded shared library.
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+set testfile type-opaque-main
+set libfile type-opaque-lib
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+
+set libsrc "${srcdir}/${subdir}/${libfile}.c"
+set libobj "${objdir}/${subdir}/${libfile}.so"
+set execsrc "${srcdir}/${subdir}/${srcfile}"
+
+remote_exec build "rm -f ${binfile}"
+
+# Are we on a target board?  No support for downloading shared libraries
+# to a target yet.
+if ![isnative] then {
+    return 0
+}
+
+# get the value of gcc_compiled
+if [get_compiler_info ${binfile}] {
+    return -1
+}
+
+if { [gdb_compile_shlib $libsrc $libobj {debug}] != ""
+     || [gdb_compile $execsrc ${binfile} executable \
+	     [list debug shlib=${libobj}]] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+if ![runto_main] then {
+    fail "Can't run to main"
+    return 0
+}
+
+
+# DWARF3: An incomplete structure, union or class type is represented by
+# a structure, union or class entry that does not have a byte size attribute
+# and that has a DW_AT_declaration attribute.
+
+
+proc body { struct } {
+    global gdb_prompt
+
+
+    # <1><15f>: Abbrev Number: 8 (DW_TAG_structure_type)
+    #     DW_AT_name        : libtype_opaque
+    #     DW_AT_declaration : 1
+
+    set name "opaque $struct type resolving"
+    gdb_test_multiple "ptype pointer_${struct}_opaque" $name \
+    {
+	-re "libfield_opaque.*$gdb_prompt $"  {
+	    pass $name
+	}
+    }
+
+
+    # <1><9e>: Abbrev Number: 2 (DW_TAG_structure_type)
+    #     DW_AT_name        : libtype_empty
+    #     DW_AT_byte_size   : 0
+    #     DW_AT_decl_file   : 1
+    #     DW_AT_decl_line   : 25
+
+    set name "empty $struct type resolving"
+    gdb_test_multiple "ptype pointer_${struct}_empty" $name \
+    {
+	-re "\\{\[ \t\r\n\]*<no data fields>\[ \t\r\n\]*\\}.*$gdb_prompt $"  {
+	    pass $name
+	}
+	-re "libfield_empty.*$gdb_prompt $"  {
+	    fail $name
+	}
+    }
+
+
+    # <1><b0>: Abbrev Number: 3 (DW_TAG_structure_type)
+    #     DW_AT_sibling     : <e3>
+    #     DW_AT_name        : libtype_filled
+    #     DW_AT_byte_size   : 4
+    #     DW_AT_decl_file   : 1
+    #     DW_AT_decl_line   : 29
+    # <2><c7>: Abbrev Number: 4 (DW_TAG_member)
+    #     DW_AT_name        : mainfield_filled
+    #     DW_AT_decl_file   : 1
+    #     DW_AT_decl_line   : 30
+    #     DW_AT_type        : <e3>
+    #     DW_AT_data_member_location: 2 byte block: 23 0     (DW_OP_plus_uconst: 0)
+
+    set name "filled $struct type resolving"
+    gdb_test_multiple "ptype pointer_${struct}_filled" $name \
+    {
+	-re "mainfield_filled.*$gdb_prompt $"  {
+	    pass $name
+	}
+	-re "libfield_filled.*$gdb_prompt $"  {
+	    fail $name
+	}
+    }
+
+
+}
+
+
+body struct
+body union