Fix strict aliasing warning in rb_int128_to_numeric

If we don't have uint128, then rb_int128_to_numeric emits a strict
aliasing warning:

    numeric.c:3641:39: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
    3641 |         return rb_uint128_to_numeric(*(rb_uint128_t*)&n);
         |                                       ^~~~~~~~~~~~~~~~~

1 files changed, 5 insertions, 0 deletions

diff --git a/internal/numeric.h b/internal/numeric.h
index 75181a7f16..d3905f048c 100644
--- a/internal/numeric.h
+++ b/internal/numeric.h
@@ -164,6 +164,11 @@ union rb_int128 {
 };
 typedef union rb_int128 rb_int128_t;
 
+union uint128_int128_conversion {
+    rb_uint128_t uint128;
+    rb_int128_t int128;
+};
+
 // Conversion functions for 128-bit integers:
 rb_uint128_t rb_numeric_to_uint128(VALUE x);
 rb_int128_t rb_numeric_to_int128(VALUE x);