On 4/5/06, Devendra Mulakkayala <dmulakkayala@xxxxxxxxxxxx> wrote:
>
> Hello,
>
> ISSUE: Facing problem with bit fields, when i am compiling my code with
> GCC. It was previously compiled with diab compiler and was working fine.
>
> In our code Union definition is as follows...,
> union
> {
> unsigned_8 indicator;
> struct
> {
> unsigned_8 unused : 6;
> unsigned_8 speed :1;
> unsigned_8 time :1;
> }bit;
> }msg;
>
> In code, speed and time bits are set as follows
>
> msg.bit.speed=TRUE;
> msg.bit.time=TRUE;
>
> Some where in code there is check for indicator as follows
>
> if(indicator==03) /* this is to check whether speed and time bits are set.
I feel this is not what you should be doing.
you should be checking
if (msg.bit.speed== TRUE && msg.bit.time==TRUE)
not what bits get set.The compiler can translate them to the correct
C0 or 03. Don't you think so ?
> If yes go iside block */
> {
> ----
> ----
> ----
> }
>
> unused 6 bits are initialized to 0.
>
> This code previously compiled with diab compiler and working fine. Now i am
> trying to compile with GCC compiler.
>
Your previous compiler was just giving you the wrong illusions .
> The problem here is
> 1. If speed and time bits are set, these bits are coming in MSB. That is it
> is coming 1100 0000 ( C0 ) instead of 0000 0011 (03 ). That why eventhough
> speed and time bits are set, condition is not satisfying because indicator
> value is 'C0' not '03'.
> 2. Compiler is assigning the memory from bottom to top for bit fields in
> the structure. Previously in diab compiler it is aligning bits from top to
> bottom, with that our code was working fine.
> 2. I know that these bit fields are compiler dependent. Is there any option
> in GCC to set the bit fields from top to bottom ( MSB to LSB )
> in structure.
> 3. As per the client requirement we are not supposed to change the code. I
> am looking for any option or any other way to solve this problem.
>
> Please help me in this
>
> Thanks....
> Mulakkayala
>
>
