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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id DE6233857825 for ; Wed, 25 May 2022 18:03:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DE6233857825 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-674-aBCHFrJrNA6yVyJgtNEG5g-1; Wed, 25 May 2022 14:02:59 -0400 X-MC-Unique: aBCHFrJrNA6yVyJgtNEG5g-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id ECA64101A54E for ; Wed, 25 May 2022 18:02:58 +0000 (UTC) Received: from blarsen.com (ovpn-116-24.gru2.redhat.com [10.97.116.24]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D282940CFD0B; Wed, 25 May 2022 18:02:57 +0000 (UTC) From: Bruno Larsen To: gdb-patches@sourceware.org Subject: [PATCH] gdb/reverse: Fix stepping over recursive functions Date: Wed, 25 May 2022 15:02:47 -0300 Message-Id: <20220525180247.29731-1-blarsen@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII"; x-default=true X-Spam-Status: No, score=-12.3 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, 25 May 2022 18:03:04 -0000 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" -- 2.31.1