Found the following significant warnings:
  zbsubs.c:258:15: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:258:25: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:664:15: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:664:25: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:981:15: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:981:25: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:1299:15: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:1299:25: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:1700:15: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:1700:25: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:2051:15: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:2051:25: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:2516:15: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:2516:25: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
  zbsubs.c:5493:11: warning: using floating point absolute value function 'fabs' when argument is of integer type [-Wabsolute-value]
See '/home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/Bessel.Rcheck/00install.out' for details.