util: add an ARRAY_SIZE helper.

Bug: None
Test: `make tests` pass
Change-Id: Iecd2015b7ff96cdd78ff61c905ad065e272c2885

4 files changed, 7 insertions, 3 deletions

diff --git a/examples/drop_privs.cpp b/examples/drop_privs.cpp
index d2b0e17..d925aa3 100644
--- a/examples/drop_privs.cpp
+++ b/examples/drop_privs.cpp
@@ -19,6 +19,7 @@
 #include <libminijail.h>
 
 #include <android-base/logging.h>
+#include <android-base/macros.h>
 
 gid_t groups[] = { 1001, 1002 };
 
@@ -56,7 +57,7 @@ int main(void) {
     minijail *j = minijail_new();
     minijail_change_user(j, "system");
     minijail_change_group(j, "system");
-    minijail_set_supplementary_gids(j, sizeof(groups) / sizeof(groups[0]), groups);
+    minijail_set_supplementary_gids(j, arraysize(groups), groups);
     // minijail_use_caps(j, CAP_TO_MASK(CAP_SETUID) | CAP_TO_MASK(CAP_SETGID));
     // minijail_use_seccomp_filter(j);
     // minijail_log_seccomp_filter_failures(j);
diff --git a/test/libminijail_test.cpp b/test/libminijail_test.cpp
index 6499a37..e457c24 100644
--- a/test/libminijail_test.cpp
+++ b/test/libminijail_test.cpp
@@ -19,6 +19,7 @@
 #include <libminijail.h>
 
 #include <android-base/logging.h>
+#include <android-base/macros.h>
 
 const uid_t kSystemUid = 1000U;
 
@@ -114,7 +115,7 @@ int main(void) {
   minijail* j = minijail_new();
   minijail_change_user(j, "system");
   minijail_change_group(j, "system");
-  size_t num_groups = sizeof(groups) / sizeof(groups[0]);
+  size_t num_groups = arraysize(groups);
   minijail_set_supplementary_gids(j, num_groups, groups);
   minijail_use_caps(j, CAP_TO_MASK(CAP_SETUID) | CAP_TO_MASK(CAP_SETGID));
   minijail_enter(j);
diff --git a/util.c b/util.c
index 58f627b..d91d068 100644
--- a/util.c
+++ b/util.c
@@ -64,7 +64,7 @@ const char *log_syscalls[] = {"connect", "send"};
 #error "Unsupported platform"
 #endif
 
-const size_t log_syscalls_len = sizeof(log_syscalls)/sizeof(log_syscalls[0]);
+const size_t log_syscalls_len = ARRAY_SIZE(log_syscalls);
 
 int lookup_syscall(const char *name)
 {
diff --git a/util.h b/util.h
index d63590e..f019f00 100644
--- a/util.h
+++ b/util.h
@@ -35,6 +35,8 @@ extern "C" {
 #define info(_msg, ...) \
 	syslog(LOG_INFO, "libminijail[%d]: " _msg, getpid(), ## __VA_ARGS__)
 
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
 extern const char *log_syscalls[];
 extern const size_t log_syscalls_len;