Re: [PATCH] pager: exit without error on SIGPIPE

[Johannes Sixt <j6t@kdbg.org>]

Am 30.01.21 um 00:48 schrieb Denton Liu:
> If the pager closes before the git command feeding the pager finishes,
> git is killed by a SIGPIPE and the corresponding exit code is 141.
> Since the pipe is just an implementation detail, it does not make sense
> for this error code to be user-facing.
> 
> Handle SIGPIPEs by simply calling exit(0) in wait_for_pager_signal().
> 
> Introduce `test-tool pager` which infinitely prints `y` to the pager in
> order to test the new behavior. This cannot be tested with any existing
> git command because there are no other commands which produce infinite
> output. Without the change to pager.c, the newly introduced test fails.
> 
> Reported-by: Vincent Lefevre <vincent@vinc17.net>
> Signed-off-by: Denton Liu <liu.denton@gmail.com>

...

> diff --git a/pager.c b/pager.c
> index ee435de675..5922d99dc8 100644
> --- a/pager.c
> +++ b/pager.c
> @@ -34,6 +34,8 @@ static void wait_for_pager_atexit(void)
>  static void wait_for_pager_signal(int signo)
>  {
>  	wait_for_pager(1);
> +	if (signo == SIGPIPE)
> +		exit(0);
>  	sigchain_pop(signo);
>  	raise(signo);
>  }
> diff --git a/t/helper/test-pager.c b/t/helper/test-pager.c
> new file mode 100644
> index 0000000000..feb68b8643
> --- /dev/null
> +++ b/t/helper/test-pager.c
> @@ -0,0 +1,12 @@
> +#include "test-tool.h"
> +#include "cache.h"
> +
> +int cmd__pager(int argc, const char **argv)
> +{
> +	if (argc > 1)
> +		usage("\ttest-tool pager");
> +
> +	setup_pager();
> +	for (;;)
> +		puts("y");
> +}

My gut feeling tells that this will end in an infinite loop on Windows.
There are no signals on Windows that would kill the upstream of a pipe.
This call site will only notice that the downstream of the pipe was
closed, when it checks for write errors.

Let me test it.

-- Hannes