From 340d00fb783658a55a1e1d0bd97c9da360bf03fd Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Tue, 6 Apr 2021 15:12:38 +0200 Subject: [PATCH] [gdb/breakpoints] Workaround missing line-table entry 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. gdb/ChangeLog: 2021-04-06 Tom de Vries PR breakpoints/25884 * infcmd.c (prepare_one_step): Using inline frame info to narrow stepping range. gdb/testsuite/ChangeLog: 2021-04-06 Tom de Vries PR breakpoints/25884 * gdb.opt/inline-cmds.exp: Remove kfail. --- gdb/ChangeLog | 6 ++++++ gdb/infcmd.c | 14 ++++++++++++++ gdb/testsuite/ChangeLog | 5 +++++ gdb/testsuite/gdb.opt/inline-cmds.exp | 17 +---------------- 4 files changed, 26 insertions(+), 16 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 0abd3dd6df1..bcd3786598f 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2021-04-06 Tom de Vries + + PR breakpoints/25884 + * infcmd.c (prepare_one_step): Using inline frame info to narrow + stepping range. + 2021-04-06 Tom de Vries PR tui/27680 diff --git a/gdb/infcmd.c b/gdb/infcmd.c index 9b0186dd391..60f25d24686 100644 --- a/gdb/infcmd.c +++ b/gdb/infcmd.c @@ -1013,6 +1013,20 @@ 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/ChangeLog b/gdb/testsuite/ChangeLog index f5fe029c049..c6063be3832 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2021-04-06 Tom de Vries + + PR breakpoints/25884 + * gdb.opt/inline-cmds.exp: Remove kfail. + 2021-04-06 Tom de Vries PR testsuite/27691 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"] -- 2.30.2