Index: uspace/lib/c/include/math.h
===================================================================
--- uspace/lib/c/include/math.h	(revision 516e7808c5e1e23b10a77bb1429054a16f6fedc3)
+++ uspace/lib/c/include/math.h	(revision a3c6a858cfa093197f83dfc3dbb82eb7f88d445b)
@@ -49,4 +49,9 @@
 #define M_SQRT2     1.41421356237309504880
 #define M_SQRT1_2   0.70710678118654752440
+
+/* GNU extensions, but GCC emits calls to them as an optimization. */
+void sincos(double, double *, double *);
+void sincosf(float, float *, float *);
+void sincosl(long double, long double *, long double *);
 
 #endif