From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id RBdqNsoYHWA8GwAAWB0awg (envelope-from ) for ; Fri, 05 Feb 2021 05:07:06 -0500 Received: by simark.ca (Postfix, from userid 112) id D7D181E939; Fri, 5 Feb 2021 05:07:06 -0500 (EST) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id DEDFA1E939 for ; Fri, 5 Feb 2021 05:07:05 -0500 (EST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 531C13857032; Fri, 5 Feb 2021 10:07:05 +0000 (GMT) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by sourceware.org (Postfix) with ESMTPS id 137C43857032 for ; Fri, 5 Feb 2021 10:07:02 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 137C43857032 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tdevries@suse.de X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3035EACF4 for ; Fri, 5 Feb 2021 10:07:01 +0000 (UTC) Subject: [PING][PATCH][gdb/breakpoints] Workaround missing line-table entry From: Tom de Vries To: gdb-patches@sourceware.org References: <20210122091509.GA30312@delia> Message-ID: <22fce456-c018-649f-2d20-9d950dc6062a@suse.de> Date: Fri, 5 Feb 2021 11:07:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210122091509.GA30312@delia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: , Errors-To: gdb-patches-bounces@sourceware.org Sender: "Gdb-patches" On 1/22/21 10:15 AM, Tom de Vries wrote: > Hi, > > When running test-case gdb.opt/inline-cmds.exp, we run into this KFAIL with > gcc: > ... > Breakpoint 7, main () at gdb.opt/inline-cmds.c:71^M > 71 result = 0; /* set breakpoint 3 here */^M > (gdb) PASS: gdb.opt/inline-cmds.exp: continue to breakpoint: consecutive func1 > next^M > 73 func1 (); /* first call */^M > (gdb) PASS: gdb.opt/inline-cmds.exp: next to first func1 > next^M > 75 marker ();^M > (gdb) KFAIL: gdb.opt/inline-cmds.exp: next to second func1 (PRMS: gdb/25884) > ... > while with clang we have instead: > ... > next^M > 74 func1 (); /* second call */^M > (gdb) PASS: gdb.opt/inline-cmds.exp: next to second func1 > ... > > The relevant bit of the test source is here in inline-cmds.c: > ... > 71 result = 0; /* set breakpoint 3 here */ > 72 > 73 func1 (); /* first call */ > 74 func1 (); /* second call */ > 75 marker (); > ... > with func1 defined as: > ... > 33 inline __attribute__((always_inline)) int func1(void) > 34 { > 35 bar (); > 36 return x * y; > 37 } > ... > > The corresponding insns are: > ... > 40050b: movl $0x0,0x200b1f(%rip) # 601034 > 400515: callq 40057b > 40051a: callq 40057b > 40051f: callq 400596 > ... > and the line number info is: > ... > Line number Starting address View Stmt > 71 0x40050b x > 35 0x400515 x > 75 0x40051f x > ... > > The line number info is missing an entry for the insn at 40051a, and that is > causing the FAIL. This is a gcc issue, filed as PR gcc/98780 -" Missing line > table entry for inlined stmt at -g -O0". > > [ For contrast, with clang we have an extra entry: > ... > Line number Starting address View Stmt > 71 0x40050b x > 35 0x400515 x > 35 0x40051a > 75 0x40051f x > ... > though it appears to be missing the start-of-statement marker. ] > > However, there is debug info that indicates that the insn at 40051a is not > part of the line table entry for the insn at 400515: > ... > <2><1c4>: Abbrev Number: 8 (DW_TAG_inlined_subroutine) > <1c5> DW_AT_abstract_origin: <0x2a2> > <1c9> DW_AT_low_pc : 0x400515 > <1d1> DW_AT_high_pc : 0x5 > <1d9> DW_AT_call_file : 1 > <1da> DW_AT_call_line : 73 > <2><1db>: Abbrev Number: 8 (DW_TAG_inlined_subroutine) > <1dc> DW_AT_abstract_origin: <0x2a2> > <1e0> DW_AT_low_pc : 0x40051a > <1e8> DW_AT_high_pc : 0x5 > <1f0> DW_AT_call_file : 1 > <1f1> DW_AT_call_line : 74 > ... > and indeed lldb manages to "next" from line 73 to line 74. > > Work around the missing line table entry, by using the inline frame info to > narrow the stepping range in prepare_one_step. > > Tested on x86_64-linux. > > Any comments? > > Thanks, > - Tom > > [gdb/breakpoints] Workaround missing line-table entry > > gdb/ChangeLog: > > 2021-01-22 Tom de Vries > > PR breakpoints/25884 > * infcmd.c (prepare_one_step): Using inline frame info to narrow > stepping range. > > gdb/testsuite/ChangeLog: > > 2021-01-22 Tom de Vries > > PR breakpoints/25884 > * gdb.opt/inline-cmds.exp: Remove kfail. > > --- > gdb/infcmd.c | 14 ++++++++++++++ > gdb/testsuite/gdb.opt/inline-cmds.exp | 17 +---------------- > 2 files changed, 15 insertions(+), 16 deletions(-) > > diff --git a/gdb/infcmd.c b/gdb/infcmd.c > index 6f0ed952de6..ecb3de31879 100644 > --- a/gdb/infcmd.c > +++ b/gdb/infcmd.c > @@ -1009,6 +1009,20 @@ prepare_one_step (thread_info *tp, struct step_command_fsm *sm) > &tp->control.step_range_start, > &tp->control.step_range_end); > > + /* There's a problem in gcc (PR gcc/98780) that causes missing line > + table entries, which results in a too large stepping range. > + Use inlined_subroutine info to make the range more narrow. */ > + if (inline_skipped_frames (tp) > 0) > + { > + symbol *sym = inline_skipped_symbol (tp); > + if (SYMBOL_CLASS (sym) == LOC_BLOCK) > + { > + const block *block = SYMBOL_BLOCK_VALUE (sym); > + if (BLOCK_END (block) < tp->control.step_range_end) > + tp->control.step_range_end = BLOCK_END (block); > + } > + } > + > tp->control.may_range_step = 1; > > /* If we have no line info, switch to stepi mode. */ > diff --git a/gdb/testsuite/gdb.opt/inline-cmds.exp b/gdb/testsuite/gdb.opt/inline-cmds.exp > index 17720c46795..981dcbb4a29 100644 > --- a/gdb/testsuite/gdb.opt/inline-cmds.exp > +++ b/gdb/testsuite/gdb.opt/inline-cmds.exp > @@ -222,22 +222,7 @@ gdb_breakpoint $line3 > gdb_continue_to_breakpoint "consecutive func1" > > gdb_test "next" ".*func1 .*first call.*" "next to first func1" > -set msg "next to second func1" > -gdb_test_multiple "next" $msg { > - -re ".*func1 .*second call.*$gdb_prompt $" { > - pass $msg > - } > - -re ".*marker .*$gdb_prompt $" { > - # This assembles to two consecutive call instructions. > - # Both appear to be at the same line, because they're > - # in the body of the same inlined function. This is > - # reasonable for the line table. GDB should take the > - # containing block and/or function into account when > - # deciding how far to step. The single line table entry > - # is actually two consecutive instances of the same line. > - kfail gdb/25884 $msg > - } > -} > +gdb_test "next" ".*func1 .*second call.*" "next to second func1" > > # It is easier when the two inlined functions are not on the same line. > set line4 [gdb_get_line_number "set breakpoint 4 here"] >