include/ceph_assert: introduce consteval_assert

`throw` in C++20's `consteval` function results in an ill-formed
program. Useful as parameters of such functions aren't const-
expressions, and thus are unsuitable for `static_assert`.

Signed-off-by: Radoslaw Zarzynski <[email protected]>

Author: rzarzynski

src/include/ceph_assert.h

@@ -144,4 +144,10 @@ using namespace ceph;
    ? _CEPH_ASSERT_VOID_CAST (0)					\
    : ::ceph::__ceph_assertf_fail (__STRING(expr), __FILE__, __LINE__, __CEPH_ASSERT_FUNCTION, __VA_ARGS__))
 
+#define consteval_assert(expr, msg)	\
+  do {					\
+    if (!(expr)) {			\
+      throw (msg);			\
+    }					\
+  } while(false)
 #endif