nan-boxing: build on older gcc.

Older GCC 4.x versions do not support diagnostic pragmas
in functions and don't have push pragmas for diagnostics.

* arith.c (flo): Put the diagnostic disabling pragma stuff
outside of the function. Instead saving and restoring
the status with push and pop, we just disable the aliasing
warning and re-instate it as a warning.

* lib.h (c_f): Likewise.

2 files changed, 16 insertions, 14 deletions

diff --git a/arith.c b/arith.c
index d135e2a4..fad3e15b 100644
--- a/arith.c
+++ b/arith.c
@@ -4268,20 +4268,17 @@ INLINE int bad_float(double d)
 #define bad_float(d) (0)
 #endif
 
+#if CONFIG_NAN_BOXING && defined __GNUC__
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
+
 val flo(double n)
 {
   if (bad_float(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();
@@ -4292,6 +4289,10 @@ val flo(double n)
   }
 }
 
+#if CONFIG_NAN_BOXING && defined __GNUC__
+#pragma GCC diagnostic warning "-Wstrict-aliasing"
+#endif
+
 double c_flo(val num, val self)
 {
 #if CONFIG_NAN_BOXING
diff --git a/lib.h b/lib.h
index c2f42408..c15e1ff5 100644
--- a/lib.h
+++ b/lib.h
@@ -621,23 +621,24 @@ INLINE ucnum c_u(val num)
 #endif
 }
 
+#if CONFIG_NAN_BOXING && defined __GNUC__
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
+
 INLINE double c_f(val num)
 {
 #if CONFIG_NAN_BOXING
   ucnum u = coerce(ucnum, num) - NAN_FLNUM_DELTA;
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wstrict-aliasing"
-#endif
   return *coerce(double *, &u);
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif
 #else
   return num->fl.n;
 #endif
 }
 
+#if CONFIG_NAN_BOXING && defined __GNUC__
+#pragma GCC diagnostic warning "-Wstrict-aliasing"
+#endif
+
 #if SIZEOF_WCHAR_T < 4 && !CONFIG_NAN_BOXING
 #define lit_noex(strlit) coerce(obj_t *,\
                                 coerce(cnum, L"\0" L ## strlit L"\0" + 1) | \