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 0B4BD395C07B for ; Wed, 8 Jun 2022 11:17:19 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 0B4BD395C07B 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-83-Bhf-pJe7MSOi-8wHNTI49w-1; Wed, 08 Jun 2022 07:17:17 -0400 X-MC-Unique: Bhf-pJe7MSOi-8wHNTI49w-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 5D1373C10144 for ; Wed, 8 Jun 2022 11:17:17 +0000 (UTC) Received: from [10.97.116.44] (ovpn-116-44.gru2.redhat.com [10.97.116.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AFBD52166B26 for ; Wed, 8 Jun 2022 11:17:16 +0000 (UTC) Message-ID: Date: Wed, 8 Jun 2022 08:17:11 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: [PING] [PATCH] gdb/reverse: Fix stepping over recursive functions To: "gdb-patches@sourceware.org" References: <20220525180247.29731-1-blarsen@redhat.com> From: Bruno Larsen In-Reply-To: <20220525180247.29731-1-blarsen@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: 7bit X-Spam-Status: No, score=-13.3 required=5.0 tests=BAYES_00, 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, 08 Jun 2022 11:17:21 -0000 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"