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# 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] {
continue
}
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
}
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