I'm using an AT91SAM7 uC and have inherited some C code which is giving me fits. When I run this code I get a data abort error. I've tracked down the offending line of code, and it appears to be caused by something like this:
n = (UINT8) ((UINT16*)(pObject->pVar))[0];
pObject->pVar points to an instance of a structure like this:
typedef __packed struct{ UINT16 v1; UINT32 v2; UINT32 v3; UINT32 v4; UINT32 v5; }OBJTYPE; OBJTYPE xxx = {0,0,0,0,0};
When I stop the debugger on the line that causes the data abort error, I can see that pObject->pVar is pointing to 0x00200173. Is the data abort error happening because that object is not on a 32-bit boundary in memory? If so, how can I [easily] fix that? I've been going through all the online doc's reading about __packed, #pragma pack(n), adding unions to typedefs, etc.; but all the things I've been trying have not fixed the problem.
Is there an easy way (besides the __at__ attribute) to get variables like the above structure to be aligned on 32-bit boundaries?
Can anyone give me a suggestion for how to resolve this problem?
Help... Dave.
"I'm still confused. I don't see how this code can work if these structures don't get aligned on 32-bit boundaries when I use __packed in their typedef's."
You never did show pObject's declaration. Is it an 'OBJTYPE*' (i.e., points to a __packed structure)? I sounds like the compiler does not agree that it's pointing to unaligned data.