### parametric_plot3d fails with floating-point parameter

u,v = var('u,v')
X = u * cos(v) - (1/3)* u^3 * cos(v*3)
Y = - u * sin(v) - (1/3) *u^3 * sin(3*v)
Z = u^2 *cos(2*v)
p = parametric_plot3d([X,Y,Z], (u,0,1),(v,0,2*pi),frame=False, color="blue")

works but with 0.9 in place of 1 in range of u produces an error. Namely,

Unhandled SIGILL: An illegal instruction occurred in Sage.
This probably occurred because a *compiled* component of Sage has a bug
in it and is not properly wrapped with sig_on(), sig_off().
Sage will now terminate.