[RFA] patch for 2384, dangling TYPE_VPTR_BASETYPE

["Doug Evans" <dje@google.com>]

[-- Attachment #1: Type: text/plain, Size: 569 bytes --]

I think(!) this patch is reasonable.  It seems to be in line with what
Jim has in mind
(based on my interpretation of your comments Jim on the gdb list -
please correct
me if I'm wrong of course).

When gdb resolves type information for class "derived" from objfile
gdb2384 (from the testcase), it fills in the TYPE_VPTR_BASETYPE field
with class "base"
from objfile gdb2384-base.so.  When the program is rerun the type
information for base-in-so-base.so is discarded leaving
TYPE_VPTR_BASETYPE dangling.

Ok to check in?  Or any suggestions for what's needed instead?

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: gdb-071213-2384-1.patch --]
[-- Type: text/x-patch; name=gdb-071213-2384-1.patch, Size: 5659 bytes --]

2007-12-13  Doug Evans  <dje@google.com>

	PR 2384
	* gdbtypes.c (fill_in_vptr_fieldno): Don't set TYPE_VPTR_FIELDNO,
	TYPE_VPTR_BASETYPE if from different objfile.

	* gdb.cp/gdb2384.exp: New file.
	* gdb.cp/gdb2384.cc: New file.
	* gdb.cp/gdb2384-base.h: New file.
	* gdb.cp/gdb2384-base.cc: New file.

Index: gdbtypes.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbtypes.c,v
retrieving revision 1.140
diff -u -p -u -p -r1.140 gdbtypes.c
--- gdbtypes.c	4 Dec 2007 23:33:00 -0000	1.140
+++ gdbtypes.c	13 Dec 2007 23:59:35 -0000
@@ -1307,8 +1307,13 @@ fill_in_vptr_fieldno (struct type *type)
 	  fill_in_vptr_fieldno (baseclass);
 	  if (TYPE_VPTR_FIELDNO (baseclass) >= 0)
 	    {
-	      TYPE_VPTR_FIELDNO (type) = TYPE_VPTR_FIELDNO (baseclass);
-	      TYPE_VPTR_BASETYPE (type) = TYPE_VPTR_BASETYPE (baseclass);
+	      /* If the type comes from a different objfile we can't use it
+		 here, it may have a different lifetime. PR 2384 */
+	      if (TYPE_OBJFILE (type) == TYPE_OBJFILE (baseclass))
+		{
+		  TYPE_VPTR_FIELDNO (type) = TYPE_VPTR_FIELDNO (baseclass);
+		  TYPE_VPTR_BASETYPE (type) = TYPE_VPTR_BASETYPE (baseclass);
+		}
 	      break;
 	    }
 	}
Index: testsuite/gdb.cp/gdb2384-base.cc
===================================================================
RCS file: testsuite/gdb.cp/gdb2384-base.cc
diff -N testsuite/gdb.cp/gdb2384-base.cc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/gdb2384-base.cc	13 Dec 2007 23:59:35 -0000
@@ -0,0 +1,12 @@
+#include "gdb2384-base.h"
+
+base::base (int _x)
+  : x (_x)
+{
+}
+
+int
+base::meth ()
+{
+  return x;
+}
Index: testsuite/gdb.cp/gdb2384-base.h
===================================================================
RCS file: testsuite/gdb.cp/gdb2384-base.h
diff -N testsuite/gdb.cp/gdb2384-base.h
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/gdb2384-base.h	13 Dec 2007 23:59:35 -0000
@@ -0,0 +1,7 @@
+class base
+{
+ public:
+  base (int _x);
+  int x;
+  virtual int meth ();
+};
Index: testsuite/gdb.cp/gdb2384.cc
===================================================================
RCS file: testsuite/gdb.cp/gdb2384.cc
diff -N testsuite/gdb.cp/gdb2384.cc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/gdb2384.cc	13 Dec 2007 23:59:35 -0000
@@ -0,0 +1,22 @@
+#include "gdb2384-base.h"
+
+class derived : public base
+{
+ public:
+  derived (int);
+};
+
+derived::derived (int _x)
+  : base (_x)
+{
+}
+
+int g;
+
+int
+main ()
+{
+  derived d (42);
+  g = d.meth (); // set breakpoint here
+  return 0;
+}
Index: testsuite/gdb.cp/gdb2384.exp
===================================================================
RCS file: testsuite/gdb.cp/gdb2384.exp
diff -N testsuite/gdb.cp/gdb2384.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/gdb2384.exp	13 Dec 2007 23:59:35 -0000
@@ -0,0 +1,99 @@
+# Copyright 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 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/>.
+
+# When gdb resolves type information for class "derived" from objfile
+# gdb2384, it use to fill in the TYPE_VPTR_BASETYPE field with class "base"
+# from objfile gdb2384-base.so.  When the program is rerun the type
+# information for base-in-so-base.so is discarded leaving
+# TYPE_VPTR_BASETYPE dangling.
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+if { [skip_cplus_tests] } { continue }
+
+set prms_id 2384
+set bug_id 0
+
+set testfile "gdb2384"
+set srcfile ${testfile}.cc
+set binfile $objdir/$subdir/$testfile
+
+set libfile "gdb2384-base"
+set libsrcfile ${libfile}.cc
+set sofile $objdir/$subdir/"${libfile}.so"
+
+# Create and source the file that provides information about the compiler
+# used to compile the test case.
+if [get_compiler_info ${binfile} "c++"] {
+    return -1
+}
+
+if { [gdb_compile_shlib $srcdir/$subdir/$libsrcfile $sofile {debug c++}] != ""
+     || [gdb_compile $srcdir/$subdir/$srcfile $binfile executable [list debug "c++" shlib=${sofile}]] != ""} {
+    untested gdb2384.exp
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+#gdb_load_shlibs ${sofile}
+
+set bp_location [gdb_get_line_number "set breakpoint here"]
+
+# Set a breakpoint with multiple locations.
+
+gdb_test "break $srcfile:$bp_location" \
+    "Breakpoint.*at.* file .*$srcfile, line.*" \
+    "set breakpoint"
+
+gdb_run_cmd
+gdb_expect {
+    -re "Breakpoint \[0-9\]+,.*main \\(.*\\).*$gdb_prompt $" {
+	pass "run to breakpoint"
+    }
+    -re "$gdb_prompt $" {
+	fail "run to breakpoint"
+    }
+    timeout {
+	fail "run to breakpoint (timeout)"
+    }
+}
+
+gdb_test "print d.meth ()" \
+    ".*42.*" \
+    "print d.meth ()"
+
+# Now try again.  gdb's without the fix will hopefully segv here
+
+gdb_run_cmd
+gdb_expect {
+    -re "Breakpoint \[0-9\]+,.*main \\(.*\\).*$gdb_prompt $" {
+	pass "run to breakpoint #2"
+    }
+    -re "$gdb_prompt $" {
+	fail "run to breakpoint #2"
+    }
+    timeout {
+	fail "run to breakpoint #2 (timeout)"
+    }
+}
+
+gdb_test "print d.meth ()" \
+    ".*42.*" \
+    "gdb2384"