From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by sourceware.org (Postfix) with ESMTPS id 1271F3890406 for ; Fri, 22 Jan 2021 09:15:13 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 1271F3890406 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 3424BAE87 for ; Fri, 22 Jan 2021 09:15:12 +0000 (UTC) Date: Fri, 22 Jan 2021 10:15:10 +0100 From: Tom de Vries To: gdb-patches@sourceware.org Subject: [PATCH][gdb/breakpoints] Workaround missing line-table entry Message-ID: <20210122091509.GA30312@delia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Status: No, score=-11.6 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, KAM_STOCKGEN, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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: Fri, 22 Jan 2021 09:15:14 -0000 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"]