sigbug

Demonstrates a Ctrl-C issue in Symfony QuestionHelper when selecting input from a list of choices.

Using Ctrl-C can leave the terminal in a broken state on Unixy platforms under certain conditions:

• When a signal handler is installed and calls exit
• When xdebug-handler restarts a process

When calling other QuestionHelper functions, Ctrl-C works okay.

Usage

# Installation
git clone https://github.com/johnstevenson/sigbug
composer update

# Demo with a signal handler
php sigbug handler

# Demo using a restart
php sigbug restart

Commands

The following information is also available from the application's Help:

• php sigbug handler -h
• php sigbug restart -h

handler

The handler command uses a signal handler to demonstrate a Ctrl-C issue in Symfony QuestionHelper when selecting input from a list (ChoiceQuestion):

php sigbug handler

The handler reports receiving a Ctrl-C signal then exits, which unfortunately leaves the terminal in a broken state. Use Ctrl-Break then Enter to restart it.

Ctrl-C will work normally if the signal handler does not call exit or when using the other QuestionHelper methods:

• php sigbug handler --no-exit
• php sigbug handler --info
• php sigbug handler --confirm

The --default option uses a signal handler that explicitly sets SIGINT to its default action (SIG_DFL). This mimics the behaviour of the child process in the restart command, which is needed because the parent sets SIGINT to be ignored (SIG_IGN) and the child process inherits this state.

Here it can be used to examine calling a new process from a parent with SIGINT ignored, by using the trap command:

trap "" SIGINT; php -r "passthru(PHP_BINARY.' sigbug handler --default');"; trap - SIGINT;

Using Ctrl-C will break the terminal, but only if PHP is the parent process. If the shell is the parent, Ctrl-C will work normally:

trap "" SIGINT; php sigbug handler --default; trap - SIGINT;

restart

The restart command uses a process restart to demonstrate a Ctrl-C issue in Symfony QuestionHelper when selecting input from a list (ChoiceQuestion):

php sigbug restart

Using Ctrl-C unfortunately leaves the terminal in a broken state. Use Ctrl-Break then Enter to restart it.

Ctrl-C will work normally if there is no restart, or when using the other QuestionHelper methods:

• php sigbug restart --none
• php sigbug restart --info
• php sigbug restart --confirm

The issue is triggered when SIGINT is set to be ignored (SIG_IGN) in the parent process, then set to its default action (SIG_DFL) in the child process because it inherited the ignored state.

When there is no restart, SIGINT remains in its initial state - which is the default action.

xdebug-handler is used for the restart, regardless of whether Xdebug is loaded or not.