Re: [PATCH] gdb: Don't let SIGWINCH interrupt waiting for remote target

[Simon Marchi <simark@simark.ca>]

Wow thanks, I didn't expect a patch when I filed the bug report, and especially
not that fast :).

> gdb/testsuite/ChangeLog:
> 
> 	PR remote/26221
> 	* gdb.server/connect-resize-quit.exp: New file.

Does the new test really belong in `gdb.server`?  I would imagine that
this directory contains tests specific to GDBserver.  This is more a
test for GDB's remote target.

> +	# Open a connection to a remote target, but use a port number that is
> +	# unlikely to actually be in use.  We want this connection to block
> +	# waiting for a remote so we can test GDB's behaviour in this blocked
> +	# state.
> +	gdb_test_no_output "set tcp connect-timeout 2"
> +
> +	set timeout_count 0
> +	while { $timeout_count < 5} {
> +	    # Try connecting.  This should block waiting for a remote to appear.
> +	    send_gdb "target remote :0\n"

What happens when trying to connect to port 0? At first I thought it would try
to connect to a random port, but that wouldn't make sense (it wouldn't be very
useful).  I confused that with trying to _bind_ to port 0.

According to this:

https://unix.stackexchange.com/questions/180492/is-it-possible-to-connect-to-tcp-port-0

It will actually try to connect to port 0, but since there's no way of binding
to port 0, it will never connect.  Smart!

So it should be fine on Linux, I don't know about other platforms.  I could imagine
other OSes returning EINVAL or something like that.  We'll see.

> +
> +	    # Now send a signal to GDB and follow up by sending some other command.
> +	    set gdb_pid [exp_pid -i [board_info host fileid]]

GDB's spawn id is available as $gdb_spawn_id.  I don't know which is better between
that and `[board_info host fileid]`, but I usually get it from $gdb_spawn_id.

> +	    remote_exec host "kill -${sig} $gdb_pid"
> +	    send_gdb "echo xxyyzz\\n\n"
> +
> +	    # Now try to figure out what GDB did.
> +	    set got_timeout false
> +	    gdb_test_multiple "" "$testname" {
> +		-re "^target remote :0\r\n:0: Connection timed out\\..*$gdb_prompt $" {
> +		    # It's possible that we didn't send the signal quickly enough.
> +		    # Maybe the testing machine is heavily loaded?
> +		    set got_timeout true
> +		}
> +		-re "^target remote :0\r\n:0: Interrupted system call\\.\r\n$gdb_prompt.*xxyyzz.*$gdb_prompt $" {
> +		    fail "$gdb_test_name (interrupted by $sig)"
> +		    return
> +		}
> +		-re "^target remote :0\r\necho xxyyzz\\\\n\r.:0: Connection timed out.\r\n$gdb_prompt.*xxyyzz.*$gdb_prompt $" {
> +		    if { $sig == "WINCH" } {
> +			pass $gdb_test_name
> +		    } else {
> +			fail "$gdb_test_name (unexpected timeout)"
> +		    }
> +		    return
> +		}
> +		-re "^target remote :0\r\nQuit\r\n$gdb_prompt.*xxyyzz.*$gdb_prompt $" {
> +		    if { $sig == "INT" } {
> +			pass $gdb_test_name
> +		    } else {
> +			fail "$gdb_test_name (unexpected QUIT)"
> +		    }
> +		    return
> +		}
> +	    }

I don't remember, what happens if none of the -re match, will that generate
a FAIL?  I just want to be sure that if GDB outputs something else, we'll
see a failure.

Simon