1 files changed, 19 insertions, 0 deletions
diff --git a/missing/signbit.c b/missing/signbit.c
new file mode 100644
index 0000000000..2f7ce8c601
--- /dev/null
+++ b/missing/signbit.c
@@ -0,0 +1,19 @@
+#include <limits.h>
+#include "ruby.h"
+
+int
+signbit(double x)
+{
+    enum {double_per_long = sizeof(double) / sizeof(long)};
+    enum {long_msb = sizeof(long) * CHAR_BIT - 1};
+    union {double d; unsigned long i[double_per_long];} u;
+    unsigned long l;
+
+    u.d = x;
+#ifdef WORDS_BIGENDIAN
+    l = u.i[0];
+#else
+    l = u.i[double_per_long - 1];
+#endif
+    return (int)(l >> long_msb);
+}