Add -e flag to a expect a given exit code

Passing this flag causes Tini to remap the given exit code to 0 when
forwarding it.

Fixes: #69

README.md

@@ -141,6 +141,22 @@ as PID 1.
 and isn't registered as a subreaper. If you don't see a warning, you're fine.*
 
 
+### Remapping exit codes ###
+
+Tini will reuse the child's exit code when exiting, but occasionally, this may
+not be exactly what you want (e.g. if your child exits with 143 after receiving
+SIGTERM). Notably, this can be an issue with Java apps.
+
+In this case, you can use the `-e` flag to remap an arbitrary exit code to 0.
+You can pass the flag multiple times if needed.
+
+For example:
+
+```
+tini -e 143 -- ...
+```
+
+
 ### Process group killing ###
 
 By default, Tini only kills its immediate child process.  This can be

ci/run_build.sh

@@ -37,6 +37,7 @@ fi
 
 echo "CC=${CC}"
 echo "CFLAGS=${CFLAGS}"
+echo "MINIMAL=${MINIMAL-}"
 echo "ARCH_SUFFIX=${ARCH_SUFFIX-}"
 echo "ARCH_NATIVE=${ARCH_NATIVE-}"
 
@@ -64,7 +65,6 @@ popd
 
 pkg_version="$(cat "${BUILD_DIR}/VERSION")"
 
-
 if [[ -n "${ARCH_NATIVE-}" ]]; then
   echo "Built native package (ARCH_NATIVE=${ARCH_NATIVE-})"
   echo "Running smoke and internal tests"

src/tini.c

@@ -5,6 +5,7 @@
 #include <sys/wait.h>
 #include <sys/prctl.h>
 
+#include <assert.h>
 #include <errno.h>
 #include <signal.h>
 #include <string.h>
@@ -33,7 +34,15 @@
 #define DEFAULT_VERBOSITY 1
 #endif
 
-#define ARRAY_LEN(x)  (sizeof(x) / sizeof(x[0]))
+#define ARRAY_LEN(x)  (sizeof(x) / sizeof((x)[0]))
+
+#define INT32_BITFIELD_SET(F, i)     ( F[(i / 32)] |=  (1 << (i % 32)) )
+#define INT32_BITFIELD_CLEAR(F, i)   ( F[(i / 32)] &= ~(1 << (i % 32)) )
+#define INT32_BITFIELD_TEST(F, i)    ( F[(i / 32)] &   (1 << (i % 32)) )
+#define INT32_BITFIELD_CHECK_BOUNDS(F, i) do {  assert(i >= 0); assert(ARRAY_LEN(F) > (uint) (i / 32)); } while(0)
+
+#define STATUS_MAX 255
+#define STATUS_MIN 0
 
 typedef struct {
    sigset_t* const sigmask_ptr;
@@ -43,13 +52,15 @@ typedef struct {
 
 static unsigned int verbosity = DEFAULT_VERBOSITY;
 
+static int32_t expect_status[(STATUS_MAX - STATUS_MIN + 1) / 32];
+
 #ifdef PR_SET_CHILD_SUBREAPER
 #define HAS_SUBREAPER 1
-#define OPT_STRING "hsvwgl"
+#define OPT_STRING "hvwgle:s"
 #define SUBREAPER_ENV_VAR "TINI_SUBREAPER"
 #else
 #define HAS_SUBREAPER 0
-#define OPT_STRING "hvwgl"
+#define OPT_STRING "hvwgle:"
 #endif
 
 #define VERBOSITY_ENV_VAR "TINI_VERBOSITY"
@@ -199,6 +210,7 @@ void print_usage(char* const name, FILE* const file) {
 	fprintf(file, "  -v: Generate more verbose output. Repeat up to 3 times.\n");
 	fprintf(file, "  -w: Print a warning when processes are getting reaped.\n");
 	fprintf(file, "  -g: Send signals to the child's process group.\n");
+	fprintf(file, "  -e EXIT_CODE: Remap EXIT_CODE (from 0 to 255) to 0.\n");
 	fprintf(file, "  -l: Show license and exit.\n");
 #endif
 
@@ -223,6 +235,24 @@ void print_license(FILE* const file) {
     }
 }
 
+int add_expect_status(char* arg) {
+	long status = 0;
+	char* endptr = NULL;
+	status = strtol(arg, &endptr, 10);
+
+	if ((endptr == NULL) || (*endptr != 0)) {
+		return 1;
+	}
+
+	if ((status < STATUS_MIN) || (status > STATUS_MAX)) {
+		return 1;
+	}
+
+	INT32_BITFIELD_CHECK_BOUNDS(expect_status, status);
+	INT32_BITFIELD_SET(expect_status, status);
+	return 0;
+}
+
 int parse_args(const int argc, char* const argv[], char* (**child_args_ptr_ptr)[], int* const parse_fail_exitcode_ptr) {
 	char* name = argv[0];
 
@@ -258,6 +288,14 @@ int parse_args(const int argc, char* const argv[], char* (**child_args_ptr_ptr)[
 				kill_process_group++;
 				break;
 
+			case 'e':
+				if (add_expect_status(optarg)) {
+					PRINT_FATAL("Not a valid option for -e: %s", optarg);
+					*parse_fail_exitcode_ptr = 1;
+					return 1;
+				}
+				break;
+
 			case 'l':
 				print_license(stdout);
 				*parse_fail_exitcode_ptr = 0;
@@ -477,6 +515,15 @@ int reap_zombies(const pid_t child_pid, int* const child_exitcode_ptr) {
 						PRINT_FATAL("Main child exited for unknown reason");
 						return 1;
 					}
+
+					// Be safe, ensure the status code is indeed between 0 and 255.
+					*child_exitcode_ptr = *child_exitcode_ptr % (STATUS_MAX - STATUS_MIN + 1);
+
+					// If this exitcode was remapped, then set it to 0.
+					INT32_BITFIELD_CHECK_BOUNDS(expect_status, *child_exitcode_ptr);
+					if (INT32_BITFIELD_TEST(expect_status, *child_exitcode_ptr)) {
+						*child_exitcode_ptr = 0;
+					}
 				} else if (warn_on_reap > 0) {
 					PRINT_WARNING("Reaped zombie process with pid=%i", current_pid);
 				}

test/run_inner_tests.py

@@ -8,7 +8,9 @@ import time
 import psutil
 import bitmap
 import re
+import itertools
 
+DEVNULL = open(os.devnull, 'wb')
 
 SIGNUM_TO_SIGNAME = dict((v, k) for k,v in signal.__dict__.items() if re.match("^SIG[A-Z]+$", k))
 
@@ -36,6 +38,29 @@ def main():
 
     subreaper_support = bool(int(os.environ["FORCE_SUBREAPER"]))
 
+    # Run the exit code test. We use POSIXLY_CORRECT here to not need --
+    # until that's the default in Tini anyways.
+    if not args_disabled:
+        print "Running exit code test for {0}".format(tini)
+        for code in range(0, 256):
+            p = subprocess.Popen(
+                [tini, '-e', str(code), '--', 'sh', '-c', "exit {0}".format(code)],
+                stdout=DEVNULL, stderr=DEVNULL
+            )
+            ret = p.wait()
+            assert ret == 0, "Inclusive exit code test failed for %s, exit: %s" % (code, ret)
+
+            other_codes = [x for x in range(0, 256) if x != code]
+            args = list(itertools.chain(*[['-e', str(x)] for x in other_codes]))
+
+            p = subprocess.Popen(
+                [tini] + args + ['sh', '-c', "exit {0}".format(code)],
+                env=dict(os.environ, POSIXLY_CORRECT="1"),
+                stdout=DEVNULL, stderr=DEVNULL
+            )
+            ret = p.wait()
+            assert ret == code, "Exclusive exit code test failed for %s, exit: %s" % (code, ret)
+
     tests = [([proxy, tini], {}),]
 
     if subreaper_support:

tpl/README.md.in

@@ -141,6 +141,22 @@ as PID 1.
 and isn't registered as a subreaper. If you don't see a warning, you're fine.*
 
 
+### Remapping exit codes ###
+
+Tini will reuse the child's exit code when exiting, but occasionally, this may
+not be exactly what you want (e.g. if your child exits with 143 after receiving
+SIGTERM). Notably, this can be an issue with Java apps.
+
+In this case, you can use the `-e` flag to remap an arbitrary exit code to 0.
+You can pass the flag multiple times if needed.
+
+For example:
+
+```
+tini -e 143 -- ...
+```
+
+
 ### Process group killing ###
 
 By default, Tini only kills its immediate child process.  This can be