gdb/testsuite/gdb.threads/pending-step.exp

# Copyright (C) 2009-2020 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/>.

# Test that a resume cancels a previously unfinished or unreported
# single-step correctly.
#
# The test consists of several threads all running the same loop.
# There is a breakpoint set in the loop, hence all threads may hit it.
# The test then issues several "next" commands in a loop.
#
# scheduler-locking must be set to the default of "off".
#
# Here's what would happen in gdbserver:
#
# 1) We issue a "continue", and wait until a thread hits the
#    breakpoint.  Could be any thread, but assume thread 1 hits it.
#
# 2) We issue a "next" --- this single-steps thread 1, and resumes all
#    other threads.
#
# 3) thread 2, due to scheduler-locking off, hits the breakpoint.
#    gdbserver stops all other threads by sending them SIGSTOPs.
#
# 4) While being stopped in step 3, thread 1 reports a SIGTRAP, that
#    corresponds to the finished single-step of step 2.  gdbserver
#    leaves the SIGTRAP pending to report later.
#
# 5) We issue another "next" --- this requests thread 2 to
#    single-step, and all other threads to continue, including thread
#    1.  Before resuming any thread, gdbserver notices that it
#    remembers from step 4 a pending SIGTRAP to report for thread 1,
#    so reports it now.
#
# 6) From GDB's perpective, this SIGTRAP can't represent a finished
#    single-step, since thread 1 was not single-stepping (it was
#    continued in step 5).  Neither does this SIGTRAP correspond to a
#    breakpoint hit.  GDB reports to the user a spurious SIGTRAP.

standard_testfile

if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable debug] != "" } {
    return -1
}

clean_restart ${binfile}

if ![runto_main] then {
    fail "can't run to main"
    return 0
}

gdb_breakpoint [gdb_get_line_number "insert breakpoint here"]
gdb_continue_to_breakpoint "continue to first breakpoint hit"

set test "next in multiple threads with breakpoints"
set iterations 20
set ok 0
for {set i 0} {$i < $iterations} {incr i} {
    set ok 0
    gdb_test_multiple "next" "$test" {
	-re " received signal SIGTRAP.*$gdb_prompt $" {
	    fail "$test (spurious SIGTRAP)"
	}
	-re "$gdb_prompt $" {
	    set ok 1
	}
    }

    if { $ok == 0 } {
	break
    }
}

if { $ok  } {
    pass "$test"
}