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From: Carl Love <cel@us.ibm.com>
To: Bruno Larsen <blarsen@redhat.com>,
	Tom de Vries <tdevries@suse.de>,
	Ulrich Weigand <Ulrich.Weigand@de.ibm.com>,
	gdb-patches@sourceware.org
Cc: cel@us.ibm.com
Subject: RE: [PATCH 2/2 version 2] fix for gdb.reverse/finish-precsave.exp and gdb.reverse/finish-reverse.exp
Date: Fri, 20 Jan 2023 12:04:53 -0800	[thread overview]
Message-ID: <71aa635593df0677811afb85409aa190bcfa4f6a.camel@us.ibm.com> (raw)
In-Reply-To: <d956a591cc7b7845495ec70023ea993e64198b73.camel@us.ibm.com>

On Thu, 2023-01-19 at 15:57 -0800, Carl Love wrote:
> Bruno, Tom:
> 
> 
> On Thu, 2023-01-19 at 08:56 -0800, Carl Love wrote:
> 
<snip>
> 
> Without the patch, when you were in the main program at "answer += 1"
> and did a reverse-next, gdb would go back thru the call to function
> bar
> and thru the call to function foo stopping in main.  That doesn't
> seem
> right to me as you have stepped back thru function foo and bar.  
> 
> With the patch the reverse-next only step back thru function bar and
> stops in function foo at the call to bar, i.e. doesn't continue to
> step
> back thru function bar.
> 
> The following is the tailcall source code with comments showing where
> the reverse-step and reverse-next stop with and without the X86 patch
> applied.  Hopefully the code below is a little easier to follow.
> Initially, the reverse-step and reverse-next tests are executed from
> the line "answer += 1;" in function main.
> 
> 
> static __attribute__ ((noinline)) int
> bar (void)
> {
>   return 42;
> }                    <- reverse-step stops here (with no patch
>                         and with X86 patch)
> 
> static __attribute__ ((noinline)) int
> foo (void)
> {
>   return bar ();     <- reverse-next stops here (patch X86 applied)
> }
> 
> int
> main (void)
> {
>   int answer;
> 
>   answer = foo ();    <- reverse-next tops here (no patch applied,
> stepped
>                          back thru both the bar and foo functions)
>   answer += 1;        <- GDB is here, now issue the reverse-step
>                          and reverse-next commands
> 
>   return answer;
> }
> 
> As a result of the change in the reverse-next instruction, the
> expected
> test results for the tailcall test need to be updated to reflect the
> fact that gdb now stops in function foo not main.
> 
> --- a/gdb/testsuite/gdb.btrace/tailcall.exp
> +++ b/gdb/testsuite/gdb.btrace/tailcall.exp
> @@ -102,9 +102,9 @@ gdb_test "reverse-step" "\[^\r\n\]*main \\(\\) at
> tailcall.c
> :37\r\n.*" \
>      "reverse-step.2"
>  gdb_test "next" "\[^\r\n\]*38.*" \
>      "next.1"
> -gdb_test "reverse-next" "\[^\r\n\]*main \\(\\) at
> tailcall.c:37\r\n.*" \
> +gdb_test "reverse-next" "\[^\r\n\]*foo \\(\\) at
> tailcall.c:29\r\n.*" \
>      "reverse-next.1"
> -gdb_test "step" "\[^\r\n\]*foo \\(\\) at tailcall.c:29\r\n.*" \
> +gdb_test "step" "\[^\r\n\]*bar \\(\\) at tailcall.c:24\r\n.*" \
>      "step.1"
>  gdb_test "finish" "\[^\r\n\]*main \\(\\) at tailcall.c:38\r\n.*" \
>      "finish.2"
> 
> With this change, the tailcall.exp test now passes on my X86 laptop.
> The PowerPC do not change since the test is not supported on PowerPC.
> 
> I will post an updated version of the X86 patch with the fixes to the
> tailcall test.  It will be version 3.  There are no changes to the
> PowerPC patch.
> 
> The gdb.btrace/rn-dl-bind.exp test passes with and without my
> patches. 
> I still can not get this test to fail on my system.  

I have been thinking about this and have decided the above change is
not what we should do.  Basically if we forward step at answer = foo();
we stop at answer += 1;.  Which is the expected behavior for next.  So,
is we are at answer += 1; and do a reverse step it should take us to
answer = foo().  It would be the opposite of the forward next.

I think I have identified the single line in the function call
set_step_info() which caused the regression in gdb.btrace/tailcall.exp.
I have so far run a few experiments and it looks like not doing the 
statement:

 tp->control.step_stack_frame_id = get_stack_frame_id (frame);

eliminates the regression in tailcall.exp. 

So far.  I need to do some more testing but it looks like there is a
couple of regressions on my X86 laptop. It looks like the expected
behavior in both of these tests is for the reverse step over a function
stops at a function call within the function not stepping all the way
back to the call of the function.  Basically, the expected behavior of
these reverse tests is not consistent across tests.  

I am not seeing any PowerPC regression failures with the above change. 
My IBM x86 machine tests are still running.

Anyway, just wanted to give people a heads up that I am pursuing
another fix and that I now think the above fix is not the best
direction to go.

                          Carl


  reply	other threads:[~2023-01-20 20:04 UTC|newest]

Thread overview: 105+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <f594ec0070a6c585e83a6d6c8b29481a86778c0f.camel@us.ibm.com>
     [not found] ` <bc6bb459f153c0c5850d4a3e5d80bbf957ec36cc.camel@de.ibm.com>
     [not found]   ` <8bce850fa1e03e798506dc170d9b57f52034a18a.camel@us.ibm.com>
     [not found]     ` <cb5875db4e1ac60475877c685e5f172770314523.camel@de.ibm.com>
     [not found]       ` <adeeeae47c4ca79b32d79aea632ff8b2a24dd93d.camel@us.ibm.com>
     [not found]         ` <86c5e9c47945894f21b1d8bf6089c730a9f0e1a5.camel@de.ibm.com>
     [not found]           ` <b1d7ea600d6bb7af487968d938566fae9d5e1745.camel@us.ibm.com>
     [not found]             ` <5f9047b9582403561d7cce998cab9184167366a1.camel@de.ibm.com>
     [not found]               ` <e7c8093c350ad475277154014a4f0bb9b472b7af.camel@us.ibm.com>
     [not found]                 ` <f8d6379aff7af076d9edcee7d2981d052b2161ee.camel@de.ibm.com>
     [not found]                   ` <5b50668cbe882c57b8c0e9dcf5be0a253713c4c6.camel@us.ibm.com>
     [not found]                     ` <51c4bfc82ac72e475e10577dc60e4d75fa48767e.camel@de.ibm.com>
     [not found]                       ` <3ea97a8aa9cccb39299adde682f92055d1986ab3.camel@us.ibm.com>
     [not found]                         ` <f5ea8da12631f2496ba0e2263e65a0adc7ac56ca.camel@de.ibm.com>
     [not found]                           ` <53878e37c6e57de1d04d9c9960c5d0a74324ee6e.camel@us.ibm.com>
     [not found]                             ` <a5300b64533fdc753c1d50fa0e6efc21b5457547.camel@de.ibm.com>
     [not found]                               ` <50474aa92ba82eff05cdc8f49001eae56be29670.camel@us.ibm.com>
     [not found]                                 ` <f3ef4486c4ba051024602928acdfe5ddf6942b82.camel@de.ibm.com>
     [not found]                                   ` <dae6c9790b23a90d5f1494f5b6798346444f257e.camel@us.ibm.com>
     [not found]                                     ` <89331c26795e3f7743e1e068dce43b3c2dd53008.camel@us.ibm.com>
     [not found]                                       ` <c10a008e441666e4edb0916842d8eefe83f5b2f9.camel@de.ibm.com>
     [not found]                                         ` <071f24ecf9b3a2bbbe8fee7db77492eb55c5f3ff.camel@us.ibm.com>
     [not found]                                           ` <1d9b21914354bef6a290ac30673741e722e11757.camel@de.ibm.com>
2023-01-11 18:27                                             ` [PATCH 0/2] " Carl Love
2023-01-11 18:27                                             ` [PATCH 1/2] " Carl Love
2023-01-12 16:56                                               ` Tom de Vries
2023-01-12 18:54                                                 ` Carl Love
2023-01-13 13:33                                               ` Bruno Larsen
2023-01-13 16:43                                                 ` Carl Love
2023-01-13 17:04                                                   ` Bruno Larsen
2023-01-13 19:10                                                     ` Carl Love
2023-01-14 18:08                                                 ` Carl Love
2023-01-16 12:31                                                   ` Bruno Larsen
2023-01-16 16:37                                                     ` [PATCH 0/2 version 2] " Carl Love
2023-01-16 16:37                                                     ` [PATCH 1/2 " Carl Love
2023-01-17 12:35                                                       ` Bruno Larsen
2023-01-20  0:03                                                         ` [PATCH 1/2 version 3] " Carl Love
2023-01-23 19:17                                                           ` Pedro Alves
2023-01-23 21:13                                                             ` Carl Love
2023-01-24 14:08                                                               ` Pedro Alves
2023-01-24 14:23                                                                 ` Bruno Larsen
2023-01-24 15:06                                                                   ` Pedro Alves
2023-01-24 16:04                                                                     ` Bruno Larsen
2023-01-24 19:12                                                                       ` Pedro Alves
2023-01-25  9:49                                                                         ` Bruno Larsen
2023-01-25 14:11                                                                         ` Ulrich Weigand
2023-01-25 16:42                                                                           ` Pedro Alves
2023-01-25 17:13                                                                             ` Ulrich Weigand
2023-01-25 17:24                                                                               ` Pedro Alves
2023-01-25 19:38                                                                                 ` Carl Love
2023-01-24 15:51                                                                 ` Carl Love
2023-01-24 18:37                                                                   ` Pedro Alves
2023-01-24 18:25                                                                 ` Carl Love
2023-01-24 19:21                                                                   ` Pedro Alves
2023-01-24 19:26                                                                     ` Pedro Alves
2023-01-31  0:17                                                                 ` Reverse-next bug test case Carl Love
2023-02-01 14:37                                                                   ` Pedro Alves
2023-02-01 18:40                                                                     ` Carl Love
2023-01-24 15:53                                                             ` [PATCH 1/2 version 3] fix for gdb.reverse/finish-precsave.exp and gdb.reverse/finish-reverse.exp Tom de Vries
2023-01-24 18:48                                                               ` Pedro Alves
2023-01-16 16:37                                                     ` [PATCH 2/2 version 2] " Carl Love
2023-01-17 14:29                                                       ` Bruno Larsen
2023-01-17 16:36                                                         ` Carl Love
2023-01-17 16:55                                                           ` Tom de Vries
2023-01-17 17:03                                                             ` Carl Love
2023-01-17 17:14                                                               ` Tom de Vries
2023-01-17 19:31                                                                 ` Carl Love
2023-01-18 10:55                                                                   ` Tom de Vries
2023-01-18 16:16                                                                     ` Carl Love
2023-01-18 22:26                                                                     ` Carl Love
2023-01-19  8:04                                                                       ` Bruno Larsen
2023-01-19 16:56                                                                         ` Carl Love
2023-01-19 23:57                                                                           ` Carl Love
2023-01-20 20:04                                                                             ` Carl Love [this message]
2023-01-23 16:42                                                                               ` [PATCH 1/2 version 3] " Carl Love
2023-01-23 16:42                                                                               ` [PATCH 2/2 " Carl Love
2023-02-10 20:55                                                                               ` [PATCH ] PowerPC: " Carl Love
2023-02-17 12:24                                                                                 ` Ulrich Weigand
2023-02-20 16:34                                                                                   ` Carl Love
2023-02-20 16:48                                                                                     ` Bruno Larsen
2023-02-20 20:24                                                                                   ` Carl Love
2023-02-27 16:09                                                                                     ` [PING] " Carl Love
2023-02-28 13:39                                                                                     ` Bruno Larsen
2023-02-28 16:19                                                                                       ` Carl Love
2023-03-01 13:43                                                                                     ` Tom de Vries
2023-03-01 16:26                                                                                       ` Carl Love
2023-03-01 14:03                                                                                     ` Tom de Vries
2023-03-01 16:43                                                                                       ` Carl Love
2023-03-01 14:34                                                                                     ` Tom de Vries
2023-03-01 20:39                                                                                       ` Carl Love
2023-03-01 20:59                                                                                         ` [PATCH 0/2 " Carl Love
2023-03-01 20:59                                                                                         ` [PATCH 1/2] " Carl Love
2023-03-03 11:56                                                                                           ` Bruno Larsen
2023-03-08 16:19                                                                                             ` [PING] " Carl Love
2023-03-09 16:09                                                                                               ` Carl Love
2023-03-09 19:03                                                                                           ` Tom Tromey
2023-03-09 21:42                                                                                             ` Carl Love
2023-03-09 21:54                                                                                             ` [PATCH 1/2 ver 2] " Carl Love
2023-03-10  3:53                                                                                               ` Tom Tromey
2023-03-01 20:59                                                                                         ` [PATCH 2/2 ] " Carl Love
2023-03-08 16:19                                                                                           ` [PING] " Carl Love
2023-03-09 16:09                                                                                             ` Carl Love
2023-03-13 14:16                                                                                           ` Ulrich Weigand
2023-03-13 17:31                                                                                             ` Carl Love
2023-03-13 17:38                                                                                             ` [PATCH 2/2 ver2] " Carl Love
2023-03-17 17:19                                                                                               ` Ulrich Weigand
2023-03-17 23:05                                                                                                 ` Tom de Vries
2023-03-20 15:04                                                                                                   ` Carl Love
2023-03-20 23:21                                                                                                   ` Carl Love
2023-03-21  3:17                                                                                                     ` Carl Love
2023-03-21  6:52                                                                                                       ` Ulrich Weigand
2023-03-24 17:23                                                                                           ` [PATCH 2/2 ] " Simon Marchi
2023-03-24 22:16                                                                                             ` Carl Love
2023-03-25 12:39                                                                                               ` Simon Marchi
2023-03-27 23:59                                                                                                 ` Carl Love
2023-03-28  1:19                                                                                                   ` Simon Marchi
2023-03-28 15:17                                                                                                     ` Carl Love
2023-03-28 15:38                                                                                                       ` Simon Marchi
2023-07-20 12:01                                                                                                         ` Bruno Larsen
2023-07-20 14:45                                                                                                           ` Carl Love
2023-07-21  7:24                                                                                                             ` Bruno Larsen
2023-07-31 22:59                                                                                                               ` Carl Love
2023-08-02  9:29                                                                                                                 ` Bruno Larsen
2023-08-02 15:11                                                                                                                   ` Carl Love
2023-01-13 15:42                                               ` [PATCH 1/2] " Bruno Larsen
2023-01-11 18:27                                             ` [PATCH 2/2] " Carl Love
2023-01-13 15:55                                               ` Bruno Larsen
2023-01-14 18:08                                                 ` Carl Love

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