libm: explain the hard-coded _BSD_SOURCE better.
Change-Id: I2d3162f88aab49f111af3bdedc1205ad34f9fea2
diff --git a/libm/freebsd-compat.h b/libm/freebsd-compat.h
index f1985d2..9555ff9 100644
--- a/libm/freebsd-compat.h
+++ b/libm/freebsd-compat.h
@@ -16,6 +16,10 @@
#pragma once
+// Since we're implementing all the extensions,
+// we need to make sure we get all their declarations when we include <math.h>.
+#define _BSD_SOURCE
+
// Some FreeBSD source includes <complex.h> and assumes <math.h> from that.
#include <math.h>