Re: [PATCH] t7006: clean up SIGPIPE handling in trace2 tests

[Jeff King <peff@peff.net>]

On Sun, Nov 21, 2021 at 11:51:54PM -0500, Jeff King wrote:

> So why is it failing? It looks like trace2 reports this as code "-1"
> rather than 143. I think that is because the fix from be8fc53e36 (pager:
> properly log pager exit code when signalled, 2021-02-02) is incomplete.
> It sets WEXITSTATUS() if the pager exited, but it doesn't handle signal
> death at all. I think it needs:
> 
> diff --git a/run-command.c b/run-command.c
> index f40df01c77..ef9d1d4236 100644
> --- a/run-command.c
> +++ b/run-command.c
> @@ -555,6 +555,8 @@ static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
>  	if (in_signal) {
>  		if (WIFEXITED(status))
>  			code = WEXITSTATUS(status);
> +		else if (WIFSIGNALED(status))
> +			code = 128 + WTERMSIG(status); /* see comment below */
>  		return code;
>  	}

I'm tempted to say that this would be clearer if the in_signal code path
just followed the main logic, like this:

diff --git a/run-command.c b/run-command.c
index f40df01c77..1f58c17b6c 100644
--- a/run-command.c
+++ b/run-command.c
@@ -552,20 +552,17 @@ static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 
 	while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 		;	/* nothing */
-	if (in_signal) {
-		if (WIFEXITED(status))
-			code = WEXITSTATUS(status);
-		return code;
-	}
 
 	if (waiting < 0) {
 		failed_errno = errno;
-		error_errno("waitpid for %s failed", argv0);
+		if (!in_signal)
+			error_errno("waitpid for %s failed", argv0);
 	} else if (waiting != pid) {
-		error("waitpid is confused (%s)", argv0);
+		if (!in_signal)
+			error("waitpid is confused (%s)", argv0);
 	} else if (WIFSIGNALED(status)) {
 		code = WTERMSIG(status);
-		if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
+		if (!in_signal && code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 			error("%s died of signal %d", argv0, code);
 		/*
 		 * This return value is chosen so that code & 0xff
@@ -576,10 +573,12 @@ static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 	} else if (WIFEXITED(status)) {
 		code = WEXITSTATUS(status);
 	} else {
-		error("waitpid is confused (%s)", argv0);
+		if (!in_signal)
+			error("waitpid is confused (%s)", argv0);
 	}
 
-	clear_child_for_cleanup(pid);
+	if (!in_signal)
+		clear_child_for_cleanup(pid);
 
 	errno = failed_errno;
 	return code;

That's a lot more tedious "if (!in_signal)" checks, but:

  - we don't have to duplicate any of the actual application logic

  - we'd now cover the extra cases for waitpid failing or returning the
    wrong pid (previously if waitpid() failed we'd still look at status,
    which could contain complete garbage!)

-Peff