Does removal of global variables from a library break C ABI?

[Scott Talbert <swt@techie.net>]

In one of the library packages I maintain (hidapi), upstream removed a 
couple of global variables (my .symbols file noticed this).  See 
abipkgdiff below.

Does this break ABI?  My assessment is that it does NOT, but I would like 
to confirm.  These variables were not declared in a header file, so I 
can't see how external user code would have referenced them.

Thanks,
Scott

================ changes of 'libhidapi-hidraw.so.0.0.0'===============
  Functions changes summary: 0 Removed, 0 Changed, 0 Added function
  Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
  Function symbols changes summary: 0 Removed, 1 Added function symbol not 
referenced by debug info
  Variable symbols changes summary: 2 Removed, 0 Added variable symbols 
not referenced by debug info

  1 Added function symbol not referenced by debug info:

    [A] hid_get_device_info

  2 Removed variable symbols not referenced by debug info:

    [D] device_string_names
    [D] last_global_error_str

================ end of changes of 'libhidapi-hidraw.so.0.0.0'===============