nan-boxing: use GCC pragmas to disable aliasing warnings.

* arith.c (flo): The line of code which triggers the
aliasing diagnostic is wrapped with GNU-C-specific
pramgas that disable the diagnostic just for that line.

* lib.h (c_f): Likewise.

* configure: Drop the test which adds -Wno-strict-aliasing
to the DIAG_FLAGS;

1 files changed, 7 insertions, 0 deletions

diff --git a/arith.c b/arith.c
index 30847a4a..d135e2a4 100644
--- a/arith.c
+++ b/arith.c
@@ -4274,7 +4274,14 @@ val flo(double n)
     uw_throw(numeric_error_s, lit("out-of-range floating-point result"));
   } else {
 #if CONFIG_NAN_BOXING
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
     ucnum u = *(ucnum *) &n + NAN_FLNUM_DELTA;
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
     return coerce(val, u);
 #else
     val obj = make_obj();