From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 3587F386CE78 for ; Wed, 29 Jun 2022 18:46:29 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 3587F386CE78 Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-547-rP42_FOBMc6O-YPBAPOMHg-1; Wed, 29 Jun 2022 14:46:27 -0400 X-MC-Unique: rP42_FOBMc6O-YPBAPOMHg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 34E933C11E71 for ; Wed, 29 Jun 2022 18:46:27 +0000 (UTC) Received: from [10.97.116.55] (ovpn-116-55.gru2.redhat.com [10.97.116.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BF82A2166B26 for ; Wed, 29 Jun 2022 18:46:26 +0000 (UTC) Message-ID: <85d7b4e2-761e-aa32-b0a5-319b682666f3@redhat.com> Date: Wed, 29 Jun 2022 15:46:25 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: [PINGv4] [PATCH] gdb/reverse: Fix stepping over recursive functions From: Bruno Larsen To: "gdb-patches@sourceware.org" References: <20220525180247.29731-1-blarsen@redhat.com> <94a25d4e-5ca0-9411-8941-2c3be1d3fa4c@redhat.com> In-Reply-To: <94a25d4e-5ca0-9411-8941-2c3be1d3fa4c@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-11.6 required=5.0 tests=BAYES_00, BODY_8BITS, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 29 Jun 2022 18:46:31 -0000 ping! Cheers! Bruno Larsen On 6/22/22 15:49, Bruno Larsen wrote: > ping! > > Cheers! > Bruno Larsen > > On 6/15/22 16:21, Bruno Larsen wrote: >> ping! >> >> Cheers! >> Bruno Larsen >> >> On 6/8/22 08:17, Bruno Larsen wrote: >>> Ping! >>> >>> Cheers! >>> Bruno Larsen >>> >>> On 5/25/22 15:02, Bruno Larsen wrote: >>>> Currently, when using GDB to do reverse debugging, if we try to use the >>>> command "reverse next" to skip a recursive function, instead of skipping >>>> all of the recursive calls and stopping in the previous line, we stop at >>>> the second to last recursive call, and need to manually step backwards >>>> until we leave the first call.  This is well documented in PR gdb/16678. >>>> >>>> This bug happens because when GDB notices that a reverse step has >>>> entered into a function, GDB will add a step_resume_breakpoint at the >>>> start of the function, then single step out of the prologue once that >>>> breakpoint is hit.  Recursion poses a problem because that breakpoint will >>>> be hit many times before GDB should actually stop the inferior.  To fix >>>> this issue, when the step_resume_breakpoint is hit (and GDB is executing >>>> backwards), we analyze if the caller of the frame is the original frame >>>> where we started the "reverse next", and if it is, GDB will stop the >>>> inferior, otherwise GDB will just ignore the breakpoint. >>>> >>>> This commit also changes gdb.reverse/step-reverse.exp to contain a >>>> recursive function and attempt to both, skip it altogether, and to skip >>>> the second call from inside the first call, as this setup broke a >>>> previous version of the patch. >>>> --- >>>>   gdb/infrun.c                               | 24 +++++++++ >>>>   gdb/testsuite/gdb.reverse/step-reverse.c   | 16 +++++- >>>>   gdb/testsuite/gdb.reverse/step-reverse.exp | 59 ++++++++++++++++++++-- >>>>   3 files changed, 95 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/gdb/infrun.c b/gdb/infrun.c >>>> index 02c98b50c8c..95fb3227aa3 100644 >>>> --- a/gdb/infrun.c >>>> +++ b/gdb/infrun.c >>>> @@ -6761,6 +6761,30 @@ process_event_stop_test (struct execution_control_state *ecs) >>>>       case BPSTAT_WHAT_STEP_RESUME: >>>>         infrun_debug_printf ("BPSTAT_WHAT_STEP_RESUME"); >>>> +      /* If we are executing backwards, we are doing a "next" and the >>>> +     current frame is not the same as where we started, the >>>> +     step_resume_breakpoint we have just hit has been added to the start >>>> +     of a function so we can skip the whle function.  However, if we are >>>> +     skipping a recursive call, we only want to act as if we hit the >>>> +     breakpoint only when the caller of the current frame is the original >>>> +     frame we were single stepping from.  */ >>>> +      if (execution_direction == EXEC_REVERSE >>>> +      && ecs->event_thread->control.step_over_calls == STEP_OVER_ALL >>>> +      && !frame_id_eq (get_stack_frame_id (get_current_frame ()), >>>> +               ecs->event_thread->control.step_stack_frame_id)) >>>> +    { >>>> +      infrun_debug_printf ("We are not done with recursing yet"); >>>> +      /* If the caller's ID is not the same as the starting frame, we >>>> +         can ignore this breakpoint.  */ >>>> +      if (!frame_id_eq (frame_unwind_caller_id (get_current_frame ()), >>>> +                ecs->event_thread->control.step_stack_frame_id)) >>>> +        { >>>> +          keep_going (ecs); >>>> +          return; >>>> +        } >>>> +    } else >>>> +        infrun_debug_printf ("are we not recursing?"); >>>> + >>>>         delete_step_resume_breakpoint (ecs->event_thread); >>>>         if (ecs->event_thread->control.proceed_to_finish >>>>         && execution_direction == EXEC_REVERSE) >>>> diff --git a/gdb/testsuite/gdb.reverse/step-reverse.c b/gdb/testsuite/gdb.reverse/step-reverse.c >>>> index aea2a98541d..a390ac2580c 100644 >>>> --- a/gdb/testsuite/gdb.reverse/step-reverse.c >>>> +++ b/gdb/testsuite/gdb.reverse/step-reverse.c >>>> @@ -26,6 +26,17 @@ int callee() {        /* ENTER CALLEE */ >>>>     return myglob++;    /* ARRIVED IN CALLEE */ >>>>   }            /* RETURN FROM CALLEE */ >>>> +/* We need to make this function take more than a single instruction >>>> +   to run, otherwise it could hide PR gdb/16678, as reverse execution can >>>> +   step over a single-instruction function.  */ >>>> +int recursive_callee (int val){ >>>> +    if (val == 0) return 0; >>>> +    val /= 2; >>>> +    if (val>1) >>>> +    val++; >>>> +    return recursive_callee (val);    /* RECURSIVE CALL */ >>>> +} /* EXIT RECURSIVE FUNCTION */ >>>> + >>>>   /* A structure which, we hope, will need to be passed using memcpy.  */ >>>>   struct rhomboidal { >>>>     int rather_large[100]; >>>> @@ -51,6 +62,9 @@ int main () { >>>>      y = y + 4; >>>>      z = z + 5;    /* STEP TEST 2 */ >>>> +   /* Test that next goes over recursive calls too */ >>>> +   recursive_callee (32); /* NEXT OVER THIS RECURSION */ >>>> + >>>>      /* Test that "next" goes over a call */ >>>>      callee();    /* NEXT OVER THIS CALL */ >>>> @@ -60,7 +74,7 @@ int main () { >>>>      /* Test "stepi" */ >>>>      a[5] = a[3] - a[4]; /* FINISH TEST */ >>>>      callee();    /* STEPI TEST */ >>>> - >>>> + >>>>      /* Test "nexti" */ >>>>      callee();    /* NEXTI TEST */ >>>> diff --git a/gdb/testsuite/gdb.reverse/step-reverse.exp b/gdb/testsuite/gdb.reverse/step-reverse.exp >>>> index 997b62604d5..4f56b4785ca 100644 >>>> --- a/gdb/testsuite/gdb.reverse/step-reverse.exp >>>> +++ b/gdb/testsuite/gdb.reverse/step-reverse.exp >>>> @@ -47,9 +47,11 @@ gdb_test "step" ".*STEP TEST 1.*" "step test 1" >>>>   gdb_test "next 2" ".*NEXT TEST 2.*" "next test 2" >>>>   gdb_test "step 3" ".*STEP TEST 2.*" "step test 2" >>>> +# next through a recursive function call >>>> +gdb_test "next 2" "NEXT OVER THIS CALL.*" "next over recursion" >>>> + >>>>   # step over call >>>> -gdb_test "step" ".*NEXT OVER THIS CALL.*" "step up to call" >>>>   gdb_test "next" ".*STEP INTO THIS CALL.*" "next over call" >>>>   # step into call >>>> @@ -118,7 +120,7 @@ gdb_test_multiple "stepi" "$test_message" { >>>>   set test_message "stepi back from function call" >>>>   gdb_test_multiple "stepi" "$test_message" { >>>> -    -re "NEXTI TEST.*$gdb_prompt $" { >>>> +    -re -wrap "NEXTI TEST.*" { >>>>       pass "$test_message" >>>>       } >>>>       -re "ARRIVED IN CALLEE.*$gdb_prompt $" { >>>> @@ -143,7 +145,6 @@ gdb_test_multiple "stepi" "$test_message" { >>>>   ### >>>>   # Set reverse execution direction >>>> - >>>>   gdb_test_no_output "set exec-dir reverse" "set reverse execution" >>>>   # stepi backward thru return and into a function >>>> @@ -247,6 +248,58 @@ gdb_test_multiple "step" "$test_message" { >>>>   gdb_test "next" ".*NEXT OVER THIS CALL.*" "reverse next over call" >>>> +# Dont reverse the execution direction yet, as we will need another >>>> +# forward step after this test >>>> + >>>> +set step_out 0 >>>> +gdb_test_multiple "next" "reverse next over recursion" { >>>> +    -re -wrap ".*NEXT OVER THIS RECURSION.*" { >>>> +    pass "reverse next over recursion" >>>> +    } >>>> +    -re -wrap ".*RECURSIVE CALL.*" { >>>> +    fail "reverse next over recursion" >>>> +    set step_out 1 >>>> +    } >>>> +} >>>> +if { "$step_out" == 1 } { >>>> +    gdb_test_multiple "next" "stepping out of recursion" { >>>> +    -re -wrap "NEXT OVER THIS RECURSION.*" { >>>> +        set step_out 0 >>>> +    } >>>> +    -re -wrap ".*" { >>>> +        send_gdb "reverse-next\n" >>>> +        exp_continue >>>> +    } >>>> +    } >>>> +} >>>> + >>>> +# Step forward over recursion again so we can test stepping over calls >>>> +# inside the recursion itself. >>>> +gdb_test_no_output "set exec-dir forward" "forward again to test recursion" >>>> +gdb_test "next" "NEXT OVER THIS CALL.*" "reverse next over recursion again" >>>> +gdb_test_no_output "set exec-dir reverse" "reverse again to test recursion" >>>> + >>>> +gdb_test "step" ".*EXIT RECURSIVE FUNCTION.*" "enter recursive function" >>>> +set step_pass 1 >>>> +gdb_test_multiple "next" "step over recursion inside the recursion" { >>>> +    -re -wrap ".*EXIT RECURSIVE FUNCTION.*" { >>>> +    set step_pass 0 >>>> +    send_gdb "next\n" >>>> +    exp_continue >>>> +    } >>>> +    -re -wrap ".*NEXT OVER THIS RECURSION.*" { >>>> +    if {$step_pass} { >>>> +        pass "step over recursion inside the recursion" >>>> +    } else { >>>> +        fail "step over recursion inside the recursion" >>>> +    } >>>> +    } >>>> +    -re -wrap ".*" { >>>> +    send_gdb "next\n" >>>> +    exp_continue >>>> +    } >>>> +} >>>> + >>>>   # step/next backward with count >>>>   gdb_test "step 3" ".*REVERSE STEP TEST 1.*" "reverse step test 1"