[PATCH 5/7] run_command: encode deadly signal number in the return value

From: Johannes Sixt <j6t@kdbg.org>
Date: Jul 4, 2009, 19:26 UTC
Message-ID: <195a33e7de20a4b52df8cb8861998fbbbed0b311.1246734159.git.j6t@kdbg.org>
In-Reply-To: <ea2d8110ea70b8698bb3674ca4482db64053d841.1246734159.git.j6t@kdbg.org>

We now write the signal number in the error message if the program terminated by a signal. The negative return value is constructed such that after truncation to 8 bits it looks like a POSIX shell's $?:

   $ echo 0000 | { git upload-pack .; echo $? >&2; } | :
   error: git-upload-pack died of signal 13
   141

Previously, the exit code was 255 instead of 141.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
---
 run-command.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/run-command.c b/run-command.c
index 4b3fda0..146a8ea 100644
--- a/run-command.c
+++ b/run-command.c
@@ -248,7 +248,14 @@ static int wait_or_whine(pid_t pid, const char *argv0)
 	} else if (waiting != pid) {
 		error("waitpid is confused (%s)", argv0);
 	} else if (WIFSIGNALED(status)) {
-		error("%s died of signal", argv0);
+		code = WTERMSIG(status);
+		error("%s died of signal %d", argv0, code);
+		/*
+		 * This return value is chosen so that code & 0xff
+		 * mimics the exit code that a POSIX shell would report for
+		 * a program that died from this signal.
+		 */
+		code -= 128;
 	} else if (WIFEXITED(status)) {
 		code = WEXITSTATUS(status);
 		/*

-- 
1.6.3.17.g1665f