Re: [Sdcc-user] Z80 and bitfields

[Ken J. <Ken...@ie...>]

>From "C++: The Complete Reference", by Herbert Schildt, page 176:

  You cannot know, from machine to machine, whether the fields
  will run from right to left or from left to right; this implies
  that any code using bit-fields may have some machine
  dependencies.  Other restrictions may be imposed by various
  specific implementations, so check the user manual for your
  compiler.

A long time ago, I had two Windows C compilers that produced
bitfields in opposite directions.  I wasted a lot of time tracking
down that 'bug'.  So I no longer trust bitfields.  I like bitwise
operators better anyway.

-Ken Jackson


Hynek Sladky writes:
 > I think it is a bug because:
 > 
 > struct {
 >    unsigned short CCC:12;
 >    unsigned short READ_BL_LEN:4;
 > } CSD;
 > ----> works as expected (2 bytes long)
 > 
 > struct {
 >    unsigned short READ_BL_LEN:4;
 >    unsigned short CCC:12;
 > } CSD;
 > ----> works wrong (3 bytes long)
 > 
 > I think that this should work the same way shouldn't it?
 > Unfortunately I need the second version... :-(
 > 
 > Hynek Sladky