Re: [reverse RFC] test for restored machine state

[teawater <teawater at gmail dot com>]

OK. Looks good.

On Wed, Sep 17, 2008 at 07:54, Michael Snyder <msnyder@vmware.com> wrote:
> Here's a test for the question we've been discussing,
> about the restored machine state after reverse execution
> stops.
>
> Although it probably would have been sufficient to test
> two cases (register and memory), I went for completeness
> and tested five cases:
>  * a register variable
>  * an auto variable
>  * a function static
>  * a module static, and
>  * a module global.
>
> In each case, I let the program increment the variable.
> Then I tested whether the pre-increment value was restored
> under two conditions:
>  * continue backward to a breakpoint, and
>  * step backward.
>
> I checked each value "before" and "after", and the
> Teawater record/replay implementation passes 100 percent.
>
> I would welcome any suggestions for improving or extending
> the test.  I've suggested a few possible extensions in the
> comments.  I did a little hoop-dancing to make it as likely
> as possible that the compiler would emit a single instruction
> in the register case, so we can see that the side effect of
> the breakpoint instruction (incrementing the register variable)
> is in fact reverted.
>
>
> 2008-09-16  Michael Snyder  <msnyder@vmware.com>
>
>        * gdb.twreverse/machinestate.exp: New file.
>        * gdb.twreverse/machinestate.c: New file.
>        * gdb.twreverse/machinestate1.c: New file.
>        * gdb.twreverse/Makefile.in: Update for make clean.
>
> Index: machinestate.c
> ===================================================================
> RCS file: machinestate.c
> diff -N machinestate.c
> --- /dev/null   1 Jan 1970 00:00:00 -0000
> +++ machinestate.c      16 Sep 2008 23:43:04 -0000
> @@ -0,0 +1,101 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2008 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/>.
>  */
> +
> +/*
> + * Test restoration of machine state
> + */
> +
> +extern void hide (int);
> +
> +/* Test register variable
> +   Requires -- compiler honors 'register'.  */
> +
> +void
> +register_state (void)
> +{
> +  register int a = 0;
> +
> +  hide (a);    /* External function to defeat optimization.  */
> +  a++;         /* register_state: set breakpoint here */
> +  hide (a);    /* register post-change */
> +}
> +
> +/* Test auto variable (whatever that means).  */
> +
> +void
> +auto_state (void)
> +{
> +  auto int a = 0;
> +
> +  hide (a);    /* External function to defeat optimization.  */
> +  a++;         /* auto_state: set breakpoint here */
> +  hide (a);    /* auto post-change */
> +}
> +
> +/* Test function-static variable.  */
> +
> +void
> +function_static_state (void)
> +{
> +  static int a = 0;
> +
> +  hide (a);    /* External function to defeat optimization.  */
> +  a++;         /* function_static_state: set breakpoint here */
> +  hide (a);    /* function static post-change */
> +}
> +
> +/* Test module-static variable.  */
> +
> +static int astatic;
> +
> +void
> +module_static_state (void)
> +{
> +  astatic = 0;
> +
> +  hide (astatic);      /* External function to defeat optimization.  */
> +  astatic++;           /* module_static_state: set breakpoint here */
> +  hide (astatic);      /* module static post-change */
> +}
> +
> +/* Test module-global variable.  */
> +
> +int aglobal;
> +
> +void
> +module_global_state (void)
> +{
> +  aglobal = 0;
> +
> +  hide (aglobal);      /* External function to defeat optimization.  */
> +  aglobal++;           /* module_global_state: set breakpoint here */
> +  hide (aglobal);      /* module global post-change */
> +}
> +
> +/* main test driver */
> +
> +int
> +main (int argc, char **argv)
> +{
> +  register_state ();   /* begin main */
> +  auto_state ();
> +  function_static_state ();
> +  module_static_state ();
> +  module_global_state ();
> +
> +  return 0;            /* end main */
> +}
> Index: machinestate.exp
> ===================================================================
> RCS file: machinestate.exp
> diff -N machinestate.exp
> --- /dev/null   1 Jan 1970 00:00:00 -0000
> +++ machinestate.exp    16 Sep 2008 23:43:04 -0000
> @@ -0,0 +1,142 @@
> +# Copyright 2008 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/>.
> +
> +# Please email any bugs, comments, and/or additions to this file to:
> +# bug-gdb@prep.ai.mit.edu
> +
> +#
> +# This test tests the restoration of various kinds of machine state
> +# to their original values by reverse execution.  We will execute
> +# the program forward while it changes various types of data, and
> +# then execute it backward to see if their values get restored.
> +#
> +# The types of machine state (data) that are tested are:
> +#   register variable
> +#   auto variable
> +#   function static variable
> +#   module static variable
> +#   module global variable
> +#
> +# TODO:
> +# various, possibly including...
> +#   .bss variable, .data variable, ...
> +#   shared library variable
> +#   heap variable (pointer)...
> +#   overlay variables...
> +#
> +
> +
> +set testfile "machinestate"
> +set srcfile  ${testfile}.c
> +set srcfile1 ${testfile}1.c
> +
> +if { [prepare_for_testing machinestate.exp $testfile {machinestate.c
> machinestate1.c} ] } {
> +    return -1
> +}
> +
> +set newline "\[\r\n\]+"
> +
> +set beginmain [gdb_get_line_number " begin main " $srcfile]
> +set endmain   [gdb_get_line_number " end main "   $srcfile]
> +
> +# Test begins
> +
> +runto main
> +
> +# FIXME 'record' command should say something so we know it's working.
> +gdb_test "record" "" "start recording"
> +
> +# Proceed to end of main
> +
> +gdb_test "break $endmain" \
> +    "Breakpoint.* file .*/$srcfile, line $endmain.*" ""
> +gdb_continue_to_breakpoint "end of main" ".*/$srcfile:$endmain.*"
> +
> +###
> +###
> +###
> +
> +# Now run backward to each of several points where data is changed.
> +#
> +
> +# Module global variable
> +
> +set breakloc [gdb_get_line_number \
> +                 "module_global_state: set breakpoint here" $srcfile]
> +
> +gdb_test "tbreak $breakloc" ".*/$srcfile, line $breakloc.*" ""
> +gdb_test "reverse-continue" ".*/$srcfile:$breakloc.*" "reverse to
> $breakloc"
> +
> +gdb_test "print aglobal" ".* = 0$newline"  "module global reverse"
> +gdb_test "step"          ".* module global post-change .*" ""
> +gdb_test "print aglobal" ".* = 1$newline"  "module global forward"
> +
> +
> +# Module static variable
> +
> +set breakloc [gdb_get_line_number \
> +                 "module_static_state: set breakpoint here" $srcfile]
> +
> +gdb_test "tbreak $breakloc" ".*/$srcfile, line $breakloc.*" ""
> +gdb_test "reverse-continue" ".*/$srcfile:$breakloc.*" "reverse to
> $breakloc"
> +
> +gdb_test "print astatic" ".* = 0$newline"  "module static
> reverse-breakpoint"
> +gdb_test "step"          ".* module static post-change .*" ""
> +gdb_test "print astatic" ".* = 1$newline"  "module static forward"
> +gdb_test "reverse-step"  ".*$newline$breakloc.*" ""
> +gdb_test "print astatic" ".* = 0$newline"  "module static reverse-step"
> +
> +# Function static variable
> +
> +set breakloc [gdb_get_line_number \
> +                 "function_static_state: set breakpoint here" $srcfile]
> +
> +gdb_test "tbreak $breakloc" ".*/$srcfile, line $breakloc.*" ""
> +gdb_test "reverse-continue" ".*/$srcfile:$breakloc.*" "reverse to
> $breakloc"
> +
> +gdb_test "print a"      ".* = 0$newline"  "function static
> reverse-breakpoint"
> +gdb_test "step"         ".* function static post-change .*" ""
> +gdb_test "print a"      ".* = 1$newline"  "function static forward"
> +gdb_test "reverse-step" ".*$newline$breakloc.*" ""
> +gdb_test "print a"      ".* = 0$newline"  "function static reverse-step"
> +
> +# Auto variable
> +
> +set breakloc [gdb_get_line_number \
> +                 "auto_state: set breakpoint here" $srcfile]
> +
> +gdb_test "tbreak $breakloc" ".*/$srcfile, line $breakloc.*" ""
> +gdb_test "reverse-continue" ".*/$srcfile:$breakloc.*" "reverse to
> $breakloc"
> +
> +gdb_test "print a"      ".* = 0$newline"  "auto var reverse-breakpoint"
> +gdb_test "step"         ".* auto post-change .*" ""
> +gdb_test "print a"      ".* = 1$newline"  "auto var forward"
> +gdb_test "reverse-step" ".*$newline$breakloc.*" ""
> +gdb_test "print a"      ".* = 0$newline"  "auto var reverse-step"
> +
> +# Register variable
> +
> +set breakloc [gdb_get_line_number \
> +                 "register_state: set breakpoint here" $srcfile]
> +
> +gdb_test "tbreak $breakloc" ".*/$srcfile, line $breakloc.*" ""
> +gdb_test "reverse-continue" ".*/$srcfile:$breakloc.*" "reverse to
> $breakloc"
> +
> +gdb_test "print a"      ".* = 0$newline"  "register var reverse-breakpoint"
> +gdb_test "step"         ".* register post-change .*" ""
> +gdb_test "print a"      ".* = 1$newline"  "register var forward"
> +gdb_test "reverse-step" ".*$newline$breakloc.*" ""
> +gdb_test "print a"      ".* = 0$newline"  "register var reverse-step"
> +
> Index: machinestate1.c
> ===================================================================
> RCS file: machinestate1.c
> diff -N machinestate1.c
> --- /dev/null   1 Jan 1970 00:00:00 -0000
> +++ machinestate1.c     16 Sep 2008 23:43:04 -0000
> @@ -0,0 +1,25 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2008 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/>.
>  */
> +
> +/*
> + * Aux function for machine state test.
> + */
> +
> +void
> +hide (int x)
> +{
> +}
> Index: Makefile.in
> ===================================================================
> RCS file: /cvs/src/src/gdb/testsuite/gdb.twreverse/Attic/Makefile.in,v
> retrieving revision 1.1.2.5
> diff -u -p -r1.1.2.5 Makefile.in
> --- Makefile.in 9 Sep 2008 19:05:17 -0000       1.1.2.5
> +++ Makefile.in 16 Sep 2008 23:43:04 -0000
> @@ -1,7 +1,9 @@
>  VPATH = @srcdir@
>  srcdir = @srcdir@
>
> -EXECUTABLES   = break-reverse step-reverse return2-reverse watch-reverse
> +EXECUTABLES   = break-reverse step-reverse finish-reverse \
> +       until-reverse watch-reverse consecutive-reverse machinestate
> +
>  MISCELLANEOUS =
>
>  all info install-info dvi install uninstall installcheck check:
>
>