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c/8132: Union of struct of union of struct bit field
- From: ptrottier at invers dot fi
- To: gcc-gnats at gcc dot gnu dot org
- Date: 3 Oct 2002 10:34:36 -0000
- Subject: c/8132: Union of struct of union of struct bit field
- Reply-to: ptrottier at invers dot fi
>Number: 8132
>Category: c
>Synopsis: Union of struct of union of struct bit field
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: wrong-code
>Submitter-Id: net
>Arrival-Date: Thu Oct 03 03:36:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Philippe Trottier / Invers Oy
>Release: gcc version 3.2(i686-linux) & 3.1 Apple 20020420 (prerelease)
>Organization:
>Environment:
powerpc-Apple-macosx (Jag 10.2.1)
i686-lfs(4.0rc1)-linux
>Description:
Bit field struct don't pack bit properly(?) when they are in a Union included in a struct. I might be stupid and not know how to do that too...
>How-To-Repeat:
#include<stdio.h>
typedef union
{
struct
{
union
{
struct
{
int reserved:16;
int R:15;
}Tx;
struct
{
int R:15;
int PPS:1;
int I:15;
}Rx;
}value;
int TxRx:1;
}sample;
unsigned int Raw;
}gumpData;
typedef union
{
struct
{
union
{
struct
{
int reserved:16;
int R:15;
int TxRx:1;
}Tx;
struct
{
int R:15;
int PPS:1;
int I:15;
int TxRx:1;
}Rx;
}value;
}sample;
unsigned int Raw;
}gumpData2;
int main(void)
{
gumpData data;
gumpData2 data2;
data2.sample.value.Rx.TxRx=0;
data2.sample.value.Rx.I=12;
data2.sample.value.Rx.R=11;
data2.sample.value.Rx.PPS=0;
data.sample.TxRx=0;
data.sample.value.Rx.I=12;
data.sample.value.Rx.R=11;
data.sample.value.Rx.PPS=0;
printf("Data %x Size: %d\n",data.Raw,sizeof(data));
printf("Data2 %x Size: %d\n",data2.Raw,sizeof(data2));
return(0);
}
$ gcc test.c
$ ./a.out
Data 800c000b Size: 8
Data2 c000b Size: 4
>Fix:
Workaround : include the bitfield in both union.
>Release-Note:
>Audit-Trail:
>Unformatted: