old-cross-binutils/gdb/testsuite/gdb.base/consecutive-step-over.exp

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Consecutive step-overs trigger internal error. If a thread trips on a breakpoint that needs stepping over just after finishing a step over, GDB currently fails an assertion. This is a regression caused by the "Handle multiple step-overs." patch (99619beac6252113fed212fdb9e1ab97bface423) at https://sourceware.org/ml/gdb-patches/2014-02/msg00765.html. (gdb) x /4i $pc => 0x400540 <main+4>: movl $0x0,0x2003da(%rip) # 0x600924 <i> 0x40054a <main+14>: movl $0x1,0x2003d0(%rip) # 0x600924 <i> 0x400554 <main+24>: movl $0x2,0x2003c6(%rip) # 0x600924 <i> 0x40055e <main+34>: movl $0x3,0x2003bc(%rip) # 0x600924 <i> (gdb) PASS: gdb.base/consecutive-step-over.exp: get breakpoint addresses break *0x40054a Breakpoint 2 at 0x40054a: file ../../../src/gdb/testsuite/gdb.base/consecutive-step-over.c, line 23. (gdb) PASS: gdb.base/consecutive-step-over.exp: insn 1: set breakpoint condition $bpnum condition (gdb) PASS: gdb.base/consecutive-step-over.exp: insn 1: set condition break *0x400554 Breakpoint 3 at 0x400554: file ../../../src/gdb/testsuite/gdb.base/consecutive-step-over.c, line 24. (gdb) PASS: gdb.base/consecutive-step-over.exp: insn 2: set breakpoint condition $bpnum condition (gdb) PASS: gdb.base/consecutive-step-over.exp: insn 2: set condition break *0x40055e Breakpoint 4 at 0x40055e: file ../../../src/gdb/testsuite/gdb.base/consecutive-step-over.c, line 25. (gdb) PASS: gdb.base/consecutive-step-over.exp: insn 3: set breakpoint condition $bpnum condition (gdb) PASS: gdb.base/consecutive-step-over.exp: insn 3: set condition break 27 Breakpoint 5 at 0x400568: file ../../../src/gdb/testsuite/gdb.base/consecutive-step-over.c, line 27. (gdb) continue Continuing. ../../src/gdb/infrun.c:5200: internal-error: switch_back_to_stepped_thread: Assertion `!tp->control.trap_expected' failed. A problem internal to GDB has been detected, further debugging may prove unreliable. FAIL: gdb.base/consecutive-step-over.exp: continue to breakpoint: break here (GDB internal error) The assertion fails, because the code is not expecting that the event thread itself might need another step over. IOW, not expecting that TP in: tp = find_thread_needs_step_over (stepping_thread != NULL, stepping_thread); could be the event thread. A small fix for this would be to clear the event thread's trap_expected earlier, before asserting. But looking deeper, although currently_stepping_or_nexting_callback's intention is finding the thread that is doing a step/next, it also returns the thread that is doing a step-over dance, with trap_expected set. If there ever was a reason for that (it was I who added currently_stepping_or_nexting_callback , but I can't recall why I put trap_expected there in the first place), the only remaining reason nowadays is to aid in implementing switch_back_to_stepped_thread's assertion that is now triggering, by piggybacking on the walk over all threads, thus avoiding a separate walk. This is quite obscure, and I think we can do even better, by merging the walks that look for the stepping thread, and the walk that looks for some thread that might need a step over. Tested on x86_64 Fedora 17, native and gdbserver, and also native on top of my "software single-step on x86_64" series. gdb/ 2014-04-22 Pedro Alves <palves@redhat.com> * infrun.c (schedlock_applies): New function, factored out from find_thread_needs_step_over. (find_thread_needs_step_over): Use it. (switch_back_to_stepped_thread): Always clear trap_expected if the step over is finished. Return early if scheduler locking applies. Look for the stepping thread and a potential step-over thread with a single loop. (currently_stepping_or_nexting_callback): Delete. 2014-04-22 Pedro Alves <palves@redhat.com> * gdb.base/consecutive-step-over.c: New file. * gdb.base/consecutive-step-over.exp: New file.
2014-04-22 14:00:56 +00:00
# Copyright 2014 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# Regression test for a bug where GDB would internal error if a thread
# runs into a breakpoint that needs stepping over, just after stepping
# over another breakpoint, without a user visible stop in between.
#
standard_testfile
if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
return -1
}
if ![runto_main] then {
fail "Can't run to main"
return 0
}
# Make sure the target doesn't hide the breakpoint hits (that don't
# cause a user visible stop) from GDB.
gdb_test_no_output "set breakpoint condition-evaluation host"
set up_to_nl "\[^\r\n\]+\[\r\n\]+"
# Number of consecutive breakpoints in a row to try.
set n_insns 3
# Extract addresses of a few consecutive instructions.
set test "get breakpoint addresses"
if { [gdb_test_multiple "x /[expr $n_insns + 1]i \$pc" $test {
-re "=> $hex${up_to_nl} ($hex)${up_to_nl} ($hex)${up_to_nl} ($hex)${up_to_nl}$gdb_prompt $" {
for {set i 1} {$i <= $n_insns} {incr i} {
set bp_addrs($i) $expect_out($i,string)
}
pass $test
}
}] != 0 } {
# No use proceeding if bp_addrs wasn't set.
return
}
for {set i 1} {$i <= $n_insns} {incr i} {
with_test_prefix "insn $i" {
gdb_test "break \*$bp_addrs($i)" \
"Breakpoint $decimal at $bp_addrs($i): file .*" \
"set breakpoint"
# Give the breakpoint a condition that always fails, so that
# the thread is immediately re-resumed.
gdb_test_no_output "condition \$bpnum condition" \
"set condition"
}
}
set lineno [gdb_get_line_number "break here"]
gdb_breakpoint $lineno
gdb_continue_to_breakpoint "break here" ".*break here.*"