# Copyright 2022 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/>.

# In the past we would use glibc's buffered input for the mi tty.
# This buffering would cause problems if two commands are sent to gdb
# in a single write call, and, if the first command (excluding its
# trailing newline) exactly filled glibc's internal buffer.
#
# The solution to this problem was to stop using glibc's buffering for
# the mi tty.
#
# To test for this situation we send two command to gdb in a loop, the
# first command gets progressively bigger.  We check that gdb
# correctly sees both commands.

load_lib mi-support.exp
set MIFLAGS "-i=mi"

# Start gdb, passing ARGS to mi_gdb_start.  Then run a series of tests
# passing two commands to gdb in a single write action.  The first
# command is increasingly long, while the second command stays very
# short.
#
# Check that gdb sees, and performs, both commands.
proc run_test { args } {
    global mi_gdb_prompt
    global decimal

    gdb_exit
    if [mi_gdb_start $args] {
	return
    }

    set start 1
    set limit 2049

    mi_gdb_test "set \$a = \"FIRST COMMAND\"" ".*"
    mi_gdb_test "set \$b = \"TEST COMPLETE\"" ".*"

    for { set i $start } { $i < $limit } { incr i } {

	set cmd ""

	# Create a command that is at least `i` characters long.
	set first_cmd "-data-evaluate-expression \$a"
	while { [string length $first_cmd] < $i } {
	    set first_cmd " $first_cmd"
	}

	# We reset `i`, our loop counter, here.  When i is large this
	# should be a nop as we attempt to make the first command
	# length be i above.  However, the first time around the loop
	# we start with an i value of 1, however, we can't make a
	# command that short, so, by resetting i here we effectively
	# skip the first couple of loop iterations where i is less
	# than the minimum command length.
	set i [string length $first_cmd]
	verbose -log "length of first command is $i"

	set cmd "${first_cmd}\n-data-evaluate-expression \$b\n"

	# We need to call send_gdb ourselves here as gdb_test_multiple
	# will try to send each line of the command separately (breaking
	# the command at newline characters).  This splitting will more
	# than likely mean that gdb will see and process the first command
	# before the second command arrives, this prevents the bug from
	# triggering.
	send_gdb "$cmd"

	# Now check for output from the two commands.  We do this
	# using two calls to gdb_test_multiple, this is because the
	# echoing of the second command can sometime get mixed
	# unexpectedly with the command output, this is especially
	# likely when running using the read1 technique.
	#
	# When using a single gdb_test_multiple we need to anchor
	# patterns using a ^, however, this requires us to consume and
	# discard all lines that are not part of the output that we're
	# looking for.  However, due to the unpredictable
	# intermingling, it's much easier if we drop the ^ anchor.
	# However, with this gone dejagnu would sometimes match the
	# second comand output before the first commands output.
	#
	# This approach just looks for the first command output, then,
	# once that has been found, we start looking for the second
	# command output, this seems pretty reliable.
	set seen_first_message false
	set seen_second_message false

	gdb_test_multiple "" "look for first command output, command length $i" -prompt "$mi_gdb_prompt" {
	    -re "\\^done.*,value=\"\\\\\"FIRST COMMAND\\\\\"\"" {
		set seen_first_message true
		exp_continue
	    }
	    -re "\r\n$mi_gdb_prompt" {
		gdb_assert $seen_first_message $gdb_test_name
	    }
	}

	gdb_test_multiple "" "look for second command output, command length $i" -prompt "$mi_gdb_prompt" {
	    -re "\\^done,value=\"\\\\\"TEST COMPLETE\\\\\"\"\r\n$mi_gdb_prompt" {
		pass $gdb_test_name
		set seen_second_message true
	    }
	}

	# If one of the above tests failed then lets no waste our time
	# checking different command lengths.  The actual bug this
	# test checks for would result in a timeout, so we don't want
	# to risk lots more timeouts.
	if { ! [expr $seen_first_message && $seen_second_message ] } {
	    break
	}
    }
}

foreach_with_prefix args { "" "separate-mi-tty" } {
    run_test $args
}