Re: [PATCH] process-dies-while-detaching.exp: Exit early if GDB misses sync breakpoint

[Guinevere Larsen <blarsen@redhat.com>]

On 29/09/2023 19:53, Thiago Jung Bauermann via Gdb-patches wrote:
> I'm seeing a lot of variability in the failures of
> gdb.threads/process-dies-while-detaching.exp on aarch64-linux.  On this
> platform, a problem yet to be investigated causes GDB to miss the _exit
> breakpoint.  What happens next is random because after missing that
> breakpoint, GDB is out of sync with the inferior.  This causes the tests
> following that point in the testcase to fail in a random way.
>
> In this scenario it's better to exit the testcase early to avoid random
> results in the testsuite.
Thanks for working on this test, it has been driving me up the wall for 
a while!
>
> We are relying on gdb_continue_to_breakpoint to return the result of
> gdb_test_multiple.  This is already the case because in Tcl the return
> value of a function is the return value of the last command it runs.  But
> change gdb_continue_to_breakpoint to explicitly return this value, to make
> it clear this is the intended behaviour.
I like this change, since I didn't actually know that this was TCL's 
behavior!
>
> Tested on aarch64-linux.

I tested on x86_64 and I see no regressions.

Tested-By: Guinevere Larsen <blarsen@redhat.com>

I hope this gets approved soon!

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

> ---
>   .../gdb.threads/process-dies-while-detaching.exp       | 10 +++++-----
>   gdb/testsuite/lib/gdb.exp                              |  4 ++--
>   2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp b/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp
> index bbbe82df30cd..c7d43d7dddcc 100644
> --- a/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp
> +++ b/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp
> @@ -127,7 +127,7 @@ proc detach_and_expect_exit {inf_output_re test} {
>   
>   proc continue_to_exit_bp {} {
>       gdb_breakpoint "_exit" temporary
> -    gdb_continue_to_breakpoint "_exit" ".*_exit.*"
> +    return [gdb_continue_to_breakpoint "_exit" ".*_exit.*"]
>   }
>   
>   # If testing single-process, simply detach from the process.
> @@ -226,7 +226,7 @@ proc test_detach {multi_process cmd} {
>   	}
>   
>   	# Run to _exit in the child.
> -	continue_to_exit_bp
> +	return_if_fail [continue_to_exit_bp]
>   
>   	do_detach $multi_process $cmd "normal"
>       }
> @@ -265,13 +265,13 @@ proc test_detach_watch {wp multi_process cmd} {
>   	    # them out, and handle the case of the thread disappearing
>   	    # while doing that (on targets that need to detach from each
>   	    # thread individually).
> -	    continue_to_exit_bp
> +	    return_if_fail [continue_to_exit_bp]
>   	} else {
>   	    # Force software watchpoints.
>   	    gdb_test_no_output "set can-use-hw-watchpoints 0"
>   
>   	    # As above, but flip order, other wise things take too long.
> -	    continue_to_exit_bp
> +	    return_if_fail [continue_to_exit_bp]
>   	    gdb_test "watch globalvar" "Watchpoint $decimal: globalvar"
>   
>   	    if { $multi_process == 0 && $cmd == "continue" } {
> @@ -304,7 +304,7 @@ proc test_detach_killed_outside {multi_process cmd} {
>   	}
>   
>   	# Run to _exit in the child.
> -	continue_to_exit_bp
> +	return_if_fail [continue_to_exit_bp]
>   
>   	set childpid [get_integer_valueof "mypid" -1]
>   	if { $childpid == -1 } {
> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
> index 1b9179401c45..dfabc99fe4be 100644
> --- a/gdb/testsuite/lib/gdb.exp
> +++ b/gdb/testsuite/lib/gdb.exp
> @@ -822,14 +822,14 @@ proc gdb_continue_to_breakpoint {name {location_pattern .*}} {
>       set full_name "continue to breakpoint: $name"
>   
>       set kfail_pattern "Process record does not support instruction 0xfae64 at.*"
> -    gdb_test_multiple "continue" $full_name {
> +    return [gdb_test_multiple "continue" $full_name {
>   	-re "(?:Breakpoint|Temporary breakpoint) .* (at|in) $location_pattern\r\n$gdb_prompt $" {
>   	    pass $full_name
>   	}
>   	-re "(?:$kfail_pattern)\r\n$gdb_prompt $" {
>   	    kfail "gdb/25038" $full_name
>   	}
> -    }
> +    }]
>   }
>   
>   
>