Index: printcmd.c
===================================================================
RCS file: /cvs/src/src/gdb/printcmd.c,v
retrieving revision 1.144
diff -u -p -u -r1.144 printcmd.c
--- printcmd.c	25 Feb 2009 18:26:53 -0000	1.144
+++ printcmd.c	5 Mar 2009 23:29:35 -0000
@@ -43,6 +43,11 @@
 #include "disasm.h"
 #include "dfp.h"
 #include "valprint.h"
+#include "exceptions.h"
+#include "observer.h"
+#include "solist.h"
+#include "solib.h"
+#include "parser-defs.h"
 
 #ifdef TUI
 #include "tui/tui.h"		/* For tui_active et.al.   */
@@ -1395,7 +1400,7 @@ display_command (char *exp, int from_tty
 	  fmt.count = 0;
 	}
 
-      innermost_block = 0;
+      innermost_block = NULL;
       expr = parse_expression (exp);
 
       new = (struct display *) xmalloc (sizeof (struct display));
@@ -1519,6 +1524,25 @@ do_one_display (struct display *d)
   if (d->enabled_p == 0)
     return;
 
+  if (d->exp == NULL)
+    {
+      volatile struct gdb_exception ex;
+      TRY_CATCH (ex, RETURN_MASK_ALL)
+	{
+	  innermost_block = NULL;
+	  d->exp = parse_expression (d->exp_string);
+	  d->block = innermost_block;
+	}
+      if (ex.reason < 0)
+	{
+	  /* Can't re-parse the expression.  Disable this display item.  */
+	  d->enabled_p = 0;
+	  warning (_("Unable to display \"%s\": %s"),
+		   d->exp_string, ex.message);
+	  return;
+	}
+    }
+
   if (d->block)
     within_current_scope = contained_in (get_selected_block (0), d->block);
   else
@@ -1731,6 +1755,72 @@ disable_display_command (char *args, int
 	  p++;
       }
 }
+
+/* Return 1 if D uses SOLIB (and will become dangling when SOLIB
+   is unloaded), otherwise return 0.  */
+
+static int
+display_uses_solib_p (const struct display *d,
+		      const struct so_list *solib)
+{
+  int i;
+  struct expression *const exp = d->exp;
+
+  if (d->block != NULL
+      && solib_address (d->block->startaddr) == solib->so_name)
+    return 1;
+
+  for (i = 0; i < exp->nelts; )
+    {
+      int args, oplen = 0;
+      const union exp_element *const elts = exp->elts;
+
+      if (elts[i].opcode == OP_VAR_VALUE)
+	{
+	  const struct block *const block = elts[i + 1].block;
+	  const struct symbol *const symbol = elts[i + 2].symbol;
+	  const struct obj_section *const section =
+	    SYMBOL_OBJ_SECTION (symbol);
+
+	  if (block != NULL
+	      && solib_address (block->startaddr) == solib->so_name)
+	    return 1;
+
+	  if (section && section->objfile == solib->objfile)
+	    return 1;
+	}
+      exp->language_defn->la_exp_desc->operator_length (exp, i + 1,
+							&oplen, &args);
+      gdb_assert (oplen > 0);
+      i += oplen;
+    }
+  return 0;
+}
+
+/* display_chain items point to blocks and expressions.  Some expressions in
+   turn may point to symbols.
+   Both symbols and blocks are obstack_alloc'd on objfile_stack, and are
+   obstack_free'd when a shared library is unloaded.
+   Clear pointers that are about to become dangling.
+   Both .exp and .block fields will be restored next time we need to display
+   an item by re-parsing .exp_string field in the new execution context.  */
+
+static void
+clear_dangling_display_expressions (struct so_list *solib)
+{
+  struct display *d;
+  struct objfile *objfile = NULL;
+
+  for (d = display_chain; d; d = d->next)
+    {
+      if (d->exp && display_uses_solib_p (d, solib))
+	{
+	  xfree (d->exp);
+	  d->exp = NULL;
+	  d->block = NULL;
+	}
+    }
+}
 
 
 /* Print the value in stack frame FRAME of a variable specified by a
@@ -2367,6 +2457,8 @@ _initialize_printcmd (void)
 
   current_display_number = -1;
 
+  observer_attach_solib_unloaded (clear_dangling_display_expressions);
+
   add_info ("address", address_info,
 	    _("Describe where symbol SYM is stored."));
 
Index: solib.c
===================================================================
RCS file: /cvs/src/src/gdb/solib.c,v
retrieving revision 1.111
diff -u -p -u -r1.111 solib.c
--- solib.c	21 Feb 2009 16:14:49 -0000	1.111
+++ solib.c	5 Mar 2009 23:29:35 -0000
@@ -999,8 +999,13 @@ sharedlibrary_command (char *args, int f
 void
 no_shared_libraries (char *ignored, int from_tty)
 {
-  objfile_purge_solibs ();
+  /* The order of the two routines below is important: clear_solib notifies
+     the solib_unloaded observers, and some of these observers might need
+     access to their associated objfiles.  Therefore, we can not purge the
+     solibs' objfiles before clear_solib has been called.  */
+
   clear_solib ();
+  objfile_purge_solibs ();
 }
 
 static void
Index: testsuite/gdb.base/solib-display-lib.c
===================================================================
RCS file: testsuite/gdb.base/solib-display-lib.c
diff -N testsuite/gdb.base/solib-display-lib.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/solib-display-lib.c	5 Mar 2009 23:29:36 -0000
@@ -0,0 +1,30 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2009 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/>.  */
+
+int a_global = 41;
+#ifndef NO_B_GLOBAL
+int b_global = 42;
+#endif
+int c_global = 43;
+
+int foo () {
+  return a_global +
+#ifndef NO_B_GLOBAL
+    b_global +
+#endif
+    c_global;
+}
Index: testsuite/gdb.base/solib-display-main.c
===================================================================
RCS file: testsuite/gdb.base/solib-display-main.c
diff -N testsuite/gdb.base/solib-display-main.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/solib-display-main.c	5 Mar 2009 23:29:36 -0000
@@ -0,0 +1,32 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2009 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/>.  */
+
+extern int foo ();
+
+int main_global = 44;
+int bar ()
+{
+  int a_local = 45;
+  static int a_static = 46;
+  return main_global + a_local + a_static; /* break here */
+}
+
+int main ()
+{
+  bar ();
+  return foo ();
+}
Index: testsuite/gdb.base/solib-display.exp
===================================================================
RCS file: testsuite/gdb.base/solib-display.exp
diff -N testsuite/gdb.base/solib-display.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/solib-display.exp	5 Mar 2009 23:29:36 -0000
@@ -0,0 +1,115 @@
+# Copyright 2009 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/>.
+#
+# Contributed by Paul Pluzhnikov <ppluzhnikov@google.com>
+#
+
+# This test case verifies that if a display is active on a variable
+# which belongs in a shared library, and that shared library is
+# reloaded (e.g. due to re-execution of the program), GDB will continue
+# to display it (gdb-6.8 crashed under this scenario).
+
+# Also test that a display of variable which is currently present in
+# a shared library, but disappears before re-run, doesn't cause GDB
+# difficulties, and that it continues to display other variables.
+
+# Finally, test that displays which refer to main executable
+# (and thus aren't affected by shared library unloading) are not
+# disabled prematurely.
+
+if [skip_shlib_tests] then {
+    return 0
+}
+
+# Library file.
+set libname "solib-display-lib"
+set srcfile_lib ${srcdir}/${subdir}/${libname}.c
+set binfile_lib ${objdir}/${subdir}/${libname}.so
+set lib_flags [list debug]
+# Binary file.
+set testfile "solib-display-main"
+set srcfile ${srcdir}/${subdir}/${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+set bin_flags [list debug shlib=${binfile_lib}]
+
+if [get_compiler_info ${binfile}] {
+    return -1
+}
+
+if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} $lib_flags] != ""
+     || [gdb_compile ${srcfile} ${binfile} executable $bin_flags] != "" } {
+  untested "Could not compile $binfile_lib or $binfile."
+  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
+}
+
+gdb_test "display a_global" "1: a_global = 41"
+gdb_test "display b_global" "2: b_global = 42"
+gdb_test "display c_global" "3: c_global = 43"
+
+if { [gdb_start_cmd] < 0 } {
+    fail "Can't run to main (2)"
+    return 0
+}
+
+gdb_test "" "3: c_global = 43\\r\\n2: b_global = 42\\r\\n1: a_global = 41" "after rerun"
+
+# Now rebuild the library without b_global
+if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} \
+	  "$lib_flags additional_flags=-DNO_B_GLOBAL"] != ""} {
+    fail "Can't rebuild $binfile_lib"
+}
+
+if { [gdb_start_cmd] < 0 } {
+    fail "Can't run to main (3)"
+    return 0
+}
+
+gdb_test "" "3: c_global = 43\\r\\nwarning: .*b_global.*\\r\\n1: a_global = 41" "after rerun"
+
+# Now verify that displays which are not in the shared library
+# are not cleared permaturely.
+
+gdb_test "break [gdb_get_line_number "break here" ${testfile}.c]" \
+	".*Breakpoint.* at .*" 
+
+gdb_test "continue"
+gdb_test "display main_global" "4: main_global = 44"
+gdb_test "display a_local" "5: a_local = 45"
+gdb_test "display a_static" "6: a_static = 46"
+
+if { [gdb_start_cmd] < 0 } {
+    fail "Can't run to main (4)"
+    return 0
+}
+
+gdb_test "" "6: a_static = 46\\r\\n4: main_global = 44\\r\\n.*"
+gdb_test "break [gdb_get_line_number "break here" ${testfile}.c]" \
+	".*Breakpoint.* at .*" 
+gdb_test "continue" "6: a_static = 46\\r\\n5: a_local = 45\\r\\n4: main_global = 44\\r\\n.*"
+
+gdb_exit
+
+return 0
+
+