linux native async mode support

[Vladimir Prus]

Nick Roberts wrote:

> #
> # Test asynchronous Machine Interface (MI) operations
> #
> 
> # This currently only works with native linux and the async remote protocol.
> if { !([isnative] && [istarget *-linux*]) \
> Â  Â  Â && [board_info gdb_protocol] != "async" } then {
> Â  return
> }
> 
> # The plan is for async mode to become the default but toggle for now.
> set saved_gdbflags $GDBFLAGS
> set GDBFLAGS "-ex \"maint set linux-async on\""
> 
> load_lib mi-support.exp
> 
> gdb_exit
> if [mi_gdb_start] {
> Â  Â  continue
> }
> 
> set testfile "basics"
> set srcfile ${testfile}.c
> set binfile ${objdir}/${subdir}/${testfile}
> if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug
additional_flags=-DFAKEARGV}] != "" } {
> Â  Â  Â untested mi-async.exp
> Â  Â  Â return -1
> }
> 
> mi_delete_breakpoints
> mi_gdb_reinitialize_dir $srcdir/$subdir
> mi_gdb_load ${binfile}
> 
> # mi_gdb_test cannot be used for asynchronous commands because there are
> # two prompts involved and this can lead to a race condition.
> 
> proc linux_async_tests {} {
> Â  Â  global mi_gdb_prompt
> Â  Â  global hex
> 
>     set line_main_head     [gdb_get_line_number "main ("]
>     set line_main_body     [expr $line_main_head + 2]
>     set line_main_next     [expr $line_main_head + 3]
> 
> Â  Â  send_gdb "start\n"
> Â  Â  gdb_expect {
> Â Â Â Â Â Â Â Â -re ".*\\^running\r\n\\^done\r\n$mi_gdb_prompt" {

I don't think this is right. MI is (supposed to be) extensible. In particular, new async
notification may be added. The above will break if any notification will be emitted
between ^running and ^done and the prompt.

> Â Â Â Â Â Â Â Â  Â  Â gdb_expect {
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â -re "\\*stopped,thread-id=\"0\",frame=\{addr=\"$hex\",func=\"main\",args=\\\[\\\],file=\".*basics.c\",line=\"$line_main_body\"\}\r\n$mi_gdb_prompt$"
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â { 
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â  Â pass "Asynchronous response after start command"
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â }
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â -re ".*$mi_gdb_prompt$" {
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â  Â fail "Asynchronous response after start command (2)"
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â }
>                 timeout {
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â  Â fail "Asynchronous response after start command (timeout 2)"
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â }
> Â Â Â Â Â Â Â Â  Â  Â }
> Â Â Â Â Â Â Â Â }
> Â Â Â Â Â Â Â Â -re ".*$mi_gdb_prompt$" {
> Â Â Â Â Â Â Â Â  Â  Â fail "Asynchronous response after start command (1)"
> Â Â Â Â Â Â Â Â }
> Â Â Â Â Â Â Â Â timeout {fail "Asynchronous response after start command (timeout 1)"}
> Â  Â  }
> 
> Â  Â  send_gdb "next\n"
> Â  Â  gdb_expect {
> Â Â Â Â Â Â Â Â -re "\\^running\r\n\\^done\r\n$mi_gdb_prompt" {
> Â Â Â Â Â Â Â Â  Â  Â gdb_expect {
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â -re "\\*stopped,reason=\"end-stepping-range\",thread-id=\"0\",frame=\{addr=\"$hex\",func=\"main\",args=\\\[\\\],file=\".*basics.c\",line=\"$line_main_next\"\}\r\n$mi_gdb_prompt$"
{
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â  Â pass "Asynchronous response after next command"
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â }
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â -re ".*$mi_gdb_prompt$" {
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â  Â fail "Asynchronous response after next command (2)"
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â }
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â timeout {
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â  Â fail "Asynchronous response after next command (timeout 2)"
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â }
> Â Â Â Â Â Â Â Â  Â  Â }
> Â Â Â Â Â Â Â Â }

It appears there's a lot of duplicated logic above. Can we please have factor it out into a helper
function? This is not for the sake of abstract clarify -- I've already spend hours updating the
current MI testsuite for non-stop mode.

- Volodya