[RFC] y2038: test: Add _Static_assert() check when __USE_TIME_BITS64 is defined

[Lukasz Majewski]

This check is added to exported time/time.h file to check in the compile
time if time_t and struct timespec have proper sizes and alignment.

It shall prevent from compiling user programs with -D_TIME_BITS=64 when
time related data structures are not supporting 64 bit time.
---
 time/time.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/time/time.h b/time/time.h
index 9a74f01b2f..d293ff3dc5 100644
--- a/time/time.h
+++ b/time/time.h
@@ -446,4 +446,12 @@ extern int getdate_r (const char *__restrict __string,
 
 __END_DECLS
 
+#define CHECK_TIME64_SIZE(__name, __len) \
+  _Static_assert (sizeof (__name) == __len, "Size of " #__name " != " #__len)
+
+#ifdef __USE_TIME_BITS64
+  CHECK_TIME64_SIZE(time_t, 8);
+  CHECK_TIME64_SIZE(struct timespec, 16);
+#endif
+
 #endif /* time.h.  */
-- 
2.20.1