[patch] Fix -readnow for -gdwarf-4 unused type units

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

currently -readnow on -gdwarf-4 files often crashes GDB if any of the type
units are unused (which happens).  There are two kinds of crashes.

I find the offset field was duplicate and in some cases uninitialized.

No regressions on {x86_64,x86_64-m32,i686}-fedora15-linux-gnu with -gdwarf-4.

This is a pre-requisite how to solve the problem:
	revert+new [patch]: Re: [patch] DWARF-3+ DW_AT_accessibility defaults #2 (GCC PR debug/45124)
	http://sourceware.org/ml/gdb-patches/2011-03/msg00984.html


Thanks,
Jan


gdb/
2011-03-28  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix -readnow for -gdwarf-4 unused type units.
	* dwarf2read.c (struct signatured_type): Remove the field offset.
	(create_signatured_type_table_from_index): Remove its initialization.
	(create_debug_types_hash_table): Likewise.  Initialize per_cu.offset
	instead.  Add a complaint call.
	(process_psymtab_comp_unit): Change assignment to gdb_assert.
	(process_type_comp_unit, lookup_die_type, dump_die_shallow)
	(lookup_signatured_type_at_offset, read_signatured_type)
	(write_one_signatured_type): Update the field for per_cu.

gdb/testsuite/
2011-03-28  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix -readnow for -gdwarf-4 unused type units.
	* gdb.dwarf2/dw4-sig-type-unused.S: New file.
	* gdb.dwarf2/dw4-sig-type-unused.exp: New file.

--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -454,9 +454,6 @@ struct signatured_type
 {
   ULONGEST signature;
 
-  /* Offset in .debug_types of the TU (type_unit) for this type.  */
-  unsigned int offset;
-
   /* Offset in .debug_types of the type defined by this TU.  */
   unsigned int type_offset;
 
@@ -1902,7 +1899,6 @@ create_signatured_type_table_from_index (struct objfile *objfile,
       type_sig = OBSTACK_ZALLOC (&objfile->objfile_obstack,
 				 struct signatured_type);
       type_sig->signature = signature;
-      type_sig->offset = offset;
       type_sig->type_offset = type_offset;
       type_sig->per_cu.from_debug_types = 1;
       type_sig->per_cu.offset = offset;
@@ -3063,13 +3059,24 @@ create_debug_types_hash_table (struct objfile *objfile)
       type_sig = obstack_alloc (&objfile->objfile_obstack, sizeof (*type_sig));
       memset (type_sig, 0, sizeof (*type_sig));
       type_sig->signature = signature;
-      type_sig->offset = offset;
       type_sig->type_offset = type_offset;
       type_sig->per_cu.objfile = objfile;
       type_sig->per_cu.from_debug_types = 1;
+      type_sig->per_cu.offset = offset;
 
       slot = htab_find_slot (types_htab, type_sig, INSERT);
       gdb_assert (slot != NULL);
+      if (*slot != NULL)
+	{
+	  const struct signatured_type *dup_sig = *slot;
+
+	  complaint (&symfile_complaints,
+		     _("debug type entry at offset 0x%x is duplicate to the "
+		       "entry at offset 0x%x, signature 0x%s"),
+		     offset, dup_sig->per_cu.offset,
+		     phex (signature, sizeof (signature)));
+	  gdb_assert (signature == dup_sig->signature);
+	}
       *slot = type_sig;
 
       if (dwarf2_die_debug)
@@ -3234,8 +3241,8 @@ process_psymtab_comp_unit (struct objfile *objfile,
 
   if (this_cu->from_debug_types)
     {
-      /* offset,length haven't been set yet for type units.  */
-      this_cu->offset = cu.header.offset;
+      /* LENGTH has not been set yet for type units.  */
+      gdb_assert (this_cu->offset == cu.header.offset);
       this_cu->length = cu.header.length + cu.header.initial_length_size;
     }
   else if (comp_unit_die->tag == DW_TAG_partial_unit)
@@ -3360,7 +3367,7 @@ process_type_comp_unit (void **slot, void *info)
   gdb_assert (dwarf2_per_objfile->types.readin);
   process_psymtab_comp_unit (objfile, this_cu,
 			     dwarf2_per_objfile->types.buffer,
-			     dwarf2_per_objfile->types.buffer + entry->offset,
+			     dwarf2_per_objfile->types.buffer + this_cu->offset,
 			     dwarf2_per_objfile->types.size);
 
   return 1;
@@ -11511,7 +11518,7 @@ lookup_die_type (struct die_info *die, struct attribute *attr,
 	       die->offset, cu->objfile->name);
 
       gdb_assert (sig_type->per_cu.from_debug_types);
-      offset = sig_type->offset + sig_type->type_offset;
+      offset = sig_type->per_cu.offset + sig_type->type_offset;
       this_type = get_die_type_at_offset (offset, &sig_type->per_cu);
     }
   else
@@ -13092,7 +13099,7 @@ dump_die_shallow (struct ui_file *f, int indent, struct die_info *die)
 	case DW_FORM_ref_sig8:
 	  if (DW_SIGNATURED_TYPE (&die->attrs[i]) != NULL)
 	    fprintf_unfiltered (f, "signatured type, offset: 0x%x",
-				DW_SIGNATURED_TYPE (&die->attrs[i])->offset);
+			  DW_SIGNATURED_TYPE (&die->attrs[i])->per_cu.offset);
 	  else
 	    fprintf_unfiltered (f, "signatured type, offset: unknown");
 	  break;
@@ -13489,7 +13496,7 @@ lookup_signatured_type_at_offset (struct objfile *objfile, unsigned int offset)
   /* This is only used to lookup previously recorded types.
      If we didn't find it, it's our bug.  */
   gdb_assert (type_sig != NULL);
-  gdb_assert (offset == type_sig->offset);
+  gdb_assert (offset == type_sig->per_cu.offset);
 
   return type_sig;
 }
@@ -13528,7 +13535,7 @@ read_signatured_type (struct objfile *objfile,
   struct cleanup *back_to, *free_cu_cleanup;
 
   dwarf2_read_section (objfile, &dwarf2_per_objfile->types);
-  types_ptr = dwarf2_per_objfile->types.buffer + type_sig->offset;
+  types_ptr = dwarf2_per_objfile->types.buffer + type_sig->per_cu.offset;
 
   gdb_assert (type_sig->per_cu.cu == NULL);
 
@@ -15647,7 +15654,7 @@ write_one_signatured_type (void **slot, void *d)
 		  psymtab->n_static_syms, info->cu_index,
 		  1);
 
-  store_unsigned_integer (val, 8, BFD_ENDIAN_LITTLE, entry->offset);
+  store_unsigned_integer (val, 8, BFD_ENDIAN_LITTLE, entry->per_cu.offset);
   obstack_grow (info->types_list, val, 8);
   store_unsigned_integer (val, 8, BFD_ENDIAN_LITTLE, entry->type_offset);
   obstack_grow (info->types_list, val, 8);
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw4-sig-type-unused.S
@@ -0,0 +1,87 @@
+/* Copyright 2011 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/>.  */
+
+	.section	.debug_info
+debug_start:
+	.long	debug_end - 1f	/* Length of Compilation Unit Info */
+1:
+	.2byte	0x4	/* DWARF version number */
+	.long	.Ldebug_abbrev0	/* Offset Into Abbrev. Section */
+	.byte	0x4	/* Pointer Size (in bytes) */
+	.uleb128 0x3	/* (DIE (0xb) DW_TAG_compile_unit) */
+	.ascii "GNU C 4.4.3\0"	/* DW_AT_producer */
+	.byte	0x0c	/* DW_AT_language = DW_LANG_C99 */
+	.ascii "1.c\0"	/* DW_AT_name */
+debug_end:
+
+	.section	.debug_types
+types_start:
+	.macro	unit sig1 sig2 name
+	.long	2f - 1f	/* Length of Compilation Unit Info */
+1:
+	.2byte	0x4	/* DWARF version number */
+	.long	.Ldebug_abbrev0	/* Offset Into Abbrev. Section */
+	.byte	0x4	/* Pointer Size (in bytes) */
+	/* signature */
+	.4byte	\sig1
+	.4byte	\sig2
+	.long	3f-types_start	/* offset into type DIE */
+	.uleb128 0x1	/* DW_TAG_type_unit) */
+	.byte	0x0c	/* DW_AT_language = DW_LANG_C99 */
+3:
+	.uleb128 0x2	/* DW_TAG_structure_type */
+	.ascii	"\name"	/* DW_AT_name ... */
+	.byte	0	/* ... DW_AT_name */
+	.4byte	0	/* DW_AT_byte_size */
+	.byte	0x0	/* end of children of CU */
+2:
+	.endm
+
+	unit	0x01234567, 0x01234567, foo
+	/* One duplicate.  */
+	unit	0x01234567, 0x01234567, foo
+	/* One different, but still unused.  */
+	unit	0x89abcdef, 0x89abcdef, bar
+
+	.section	.debug_abbrev
+.Ldebug_abbrev0:
+	.uleb128 0x1	/* (abbrev code) */
+	.uleb128 0x11	/* (TAG: DW_TAG_type_unit) */
+	.byte	0x1	/* DW_children_yes */
+	.uleb128 0x13	/* (DW_AT_language) */
+	.uleb128 0xb	/* (DW_FORM_data1) */
+	.byte	0x0
+	.byte	0x0
+	.uleb128 0x2	/* (abbrev code) */
+	.uleb128 0x13	/* (TAG: DW_TAG_structure_type) */
+	.byte	0x0	/* DW_children_no */
+	.uleb128 0x3	/* (DW_AT_name) */
+	.uleb128 0x8	/* (DW_FORM_string) */
+	.uleb128 0x0b	/* (DW_AT_byte_size) */
+	.uleb128 0x6	/* (DW_FORM_data4) */
+	.byte	0x0
+	.byte	0x0
+	.uleb128 0x3	/* (abbrev code) */
+	.uleb128 0x11	/* (TAG: DW_TAG_compile_unit) */
+	.byte	0x0	/* DW_children_no */
+	.uleb128 0x25	/* (DW_AT_producer) */
+	.uleb128 0x8	/* (DW_FORM_string) */
+	.uleb128 0x13	/* (DW_AT_language) */
+	.uleb128 0xb	/* (DW_FORM_data1) */
+	.uleb128 0x3	/* (DW_AT_name) */
+	.uleb128 0x8	/* (DW_FORM_string) */
+	.byte	0x0
+	.byte	0x0
+	.byte	0x0
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw4-sig-type-unused.exp
@@ -0,0 +1,36 @@
+# Copyright 2011 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 dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0  
+}
+
+set testfile "dw4-sig-type-unused"
+set srcfile ${testfile}.S
+set executable ${testfile}.x
+set binfile ${objdir}/${subdir}/${executable}
+
+if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" object {}] != "" } {
+    return -1
+}
+
+set saved_gdbflags $GDBFLAGS
+set GDBFLAGS "$GDBFLAGS --readnow"
+clean_restart $executable
+set GDBFLAGS $saved_gdbflags
+
+gdb_test "p 1" " = 1" "alive"