Only use uids and gids for which we've allocated AIDs
Currently, getpwnam, getpwent, etc return successfully for any uid
from AID_APP_START (10000) to AID_USER_OFFSET (100000) for each user.
This is not correct however, as only specific ranges above
AID_APP_START are reserved as valid ranges. This change corrects this.
This is particularly important as the newly added AID_OVERFLOWUID is
65534, which is above AID_APP_START but not in any reserved range,
collided with the faulty returned values.
Bug: 69119022
Bug: 69128408
Test: pwd/grp bionic unit tests
Change-Id: I3dae97a90597915fa30a88fe27cda88b107e9c35
diff --git a/libc/private/bionic_macros.h b/libc/private/bionic_macros.h
index a3a3ece..979a704 100644
--- a/libc/private/bionic_macros.h
+++ b/libc/private/bionic_macros.h
@@ -78,4 +78,20 @@
#define BIONIC_STOP_UNWIND asm volatile(".cfi_undefined $ra")
#endif
+// The arraysize(arr) macro returns the # of elements in an array arr.
+// The expression is a compile-time constant, and therefore can be
+// used in defining new arrays, for example. If you use arraysize on
+// a pointer by mistake, you will get a compile-time error.
+//
+// One caveat is that arraysize() doesn't accept any array of an
+// anonymous type or a type defined inside a function.
+//
+// This template function declaration is used in defining arraysize.
+// Note that the function doesn't need an implementation, as we only
+// use its type.
+template <typename T, size_t N>
+char (&ArraySizeHelper(T (&array)[N]))[N]; // NOLINT(readability/casting)
+
+#define arraysize(array) (sizeof(ArraySizeHelper(array)))
+
#endif // _BIONIC_MACROS_H_