[ECOS] stack base pointer not align to 4 bytes

Chris Zimman czimman@bloomberg.com
Fri May 23 10:33:00 GMT 2008


> If I change the line static char g_IC_Stack[IC_STACK_SIZE]; ---------->
> static int g_IC_Stack[IC_STACK_SIZE/4]; everything is OK.
> 
> I think this is my fault, but when I grep the eCos source tree, thera
> are many files using stack definition like me( for example:
> net/tcpip/current/src/ecos/support.c). And the kernel source
> code(Cyg_HardwareThread::attach_stack()) did not adjust the alignment
> automaticly.
> 
> My fault or eCos fault? Thanks!

It's not really a 'fault' either way, but if you have it declared as char,
it's definitely not guaranteed to be word aligned.  I think the examples you
point out in eCos are probably bugs, at least on platforms that need aligned
access.

An alternative means for specifying alignment is to use
__attribute__((aligned)), eg.

static char g_IC_Stack[IC_STACK_SIZE] __attribute__((aligned(4)));

--Chris


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