[Help-bash] Why does ctrl-c behave differently for builtin sleep in a subshell?

[Peng Yu]

Hi,

See the follow code, '(/main_builtin.sh' behaves differently from the
other three scripts upon receiving ctrl-c. This is counter-intuitive.
I'd expect whether a built-in command called the result should be the
same.

How to understand why there is such a difference? Is there an easy
workaround to make the result the same as the other three?

$   ./main.sh
^Cat EXIT

$   ./main_builtin.sh
^Cat EXIT

$ \(/main.sh
^Cat EXIT

$ \(/main_builtin.sh
^C

$ cat main.sh
#!/usr/bin/env bash
trap 'echo at EXIT' EXIT
sleep 10

$ cat main_builtin.sh
#!/usr/bin/env bash
trap 'echo at EXIT' EXIT
enable -f ~/Downloads/bash-4.4/examples/loadables/sleep sleep
sleep 10

$ cat '(/main.sh'
#!/usr/bin/env bash
(
    trap 'echo at EXIT' EXIT
    sleep 10
)

$ cat '(/main_builtin.sh'
#!/usr/bin/env bash
(
    trap 'echo at EXIT' EXIT
    enable -f ~/Downloads/bash-4.4/examples/loadables/sleep sleep
    sleep 10
)

-- 
Regards,
Peng