PVS-Studio warning V610 for blender

#define cpack(x) glColor3ub( ((x)&0xFF), (((x)>>8)&0xFF), \
(((x)>>16)&0xFF) )

static void star_stuff_init_func(void)
{
  cpack(-1);
  glPointSize(1.0);
  glBegin(GL_POINTS);
}

This suspicious code was found in blender project by PVS-Studio static code analyzer.
Warning message is:
V610 Unspecified behavior. Check the shift operator '>>. The left operand '(- 1)' is negative. bf_editor_space_view3d view3d_draw.c 101

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/