run_command: encode deadly signal number in the return value

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/run-command.c b/run-command.c
index e273c6c451836148e64fa8a954348b8d9de21a60..30c2b3dd8826acd3b50ab18e8efb4ff473fd7cf2 100644 (file)
--- 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);
                /*