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 DFF2538582B4 for ; Wed, 15 Jun 2022 19:21:26 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DFF2538582B4 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-615-sDkFXqNaNcKeGyIQSkg12Q-1; Wed, 15 Jun 2022 15:21:24 -0400 X-MC-Unique: sDkFXqNaNcKeGyIQSkg12Q-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 93D3D1C0CE6C for ; Wed, 15 Jun 2022 19:21:24 +0000 (UTC) Received: from [10.97.116.32] (ovpn-116-32.gru2.redhat.com [10.97.116.32]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1447E2026D64 for ; Wed, 15 Jun 2022 19:21:23 +0000 (UTC) Message-ID: Date: Wed, 15 Jun 2022 16:21:22 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: [PINGv2] [PATCH] gdb/reverse: Fix stepping over recursive functions From: Bruno Larsen To: "gdb-patches@sourceware.org" References: <20220525180247.29731-1-blarsen@redhat.com> In-Reply-To: X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 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=-11.7 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_NONE, 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, 15 Jun 2022 19:21:29 -0000 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"