Re: [PATCH 04/12] Delete reinsert breakpoints from forked child

[Pedro Alves <palves@redhat.com>]

On 06/14/2016 12:16 PM, Yao Qi wrote:

>> >
>>> >> I think
>>> >> they've already covered by gdb.base/step-over-syscall.exp.
>> >
>> > In that case, shouldn't we be extending that test instead?
> OK, I extend step-over-syscall.exp by setting different
> combinations of follow-fork and detach-on-fork modes, and it still can
> trigger GDBserver internal errors.  How about the patch below?  

Fine with me.  One suggestion below.

> +    foreach_with_prefix detach-on-fork {"on" "off"} {
> +	foreach_with_prefix follow-fork {"parent" "child"} {
> +	    foreach syscall { "fork" "vfork" "clone" } {
> +
> +		if { $syscall != "vfork"
> +		     || ${follow-fork} != "parent"
> +		     || ${detach-on-fork} != "off" } {
> +		    # Both vforked child process and parent process are
> +		    # under GDB's control, but GDB follows the parent
> +		    # process only, which can't be run until vforked child
> +		    # finishes.  Skip the test in this scenario.
> +		    break_cond_on_syscall $syscall ${follow-fork} ${detach-on-fork}
> +		}

I'd suggest reversing the condition logic, making it match the
comment, like this:

		if { $syscall == "vfork"
		     && ${follow-fork} == "parent"
		     && ${detach-on-fork} == "off" } {
		    # Both vforked child process and parent process are
		    # under GDB's control, but GDB follows the parent
		    # process only, which can't be run until vforked child
		    # finishes.  Skip the test in this scenario.
                    continue
		}

	        break_cond_on_syscall $syscall ${follow-fork} ${detach-on-fork}


This way makes it easier to add more "skip" conditions in the future too.  E.g.,

		if { $syscall == "vfork"
		     && ${follow-fork} == "parent"
		     && ${detach-on-fork} == "off" } {
		    # Both vforked child process and parent process are
		    # under GDB's control, but GDB follows the parent
		    # process only, which can't be run until vforked child
		    # finishes.  Skip the test in this scenario.
                    continue
		}

+		if { $syscall == "whatnot"
+		     && ${follow-fork} == "parent"} {
+		    # For whatever reason, this shouldn't be tested either.
+                   continue
+		}

	        break_cond_on_syscall $syscall ${follow-fork} ${detach-on-fork}

> +	    }
> +	}
> +    }
>  }

Thanks,
Pedro Alves