But what is your CPU type ?
Some CPU's can load/save an 8 Byte (64 bit) value (such as uint64_t,
double) on a 4 Byte boundary, while some others cannot. I suspect you
need to set MEM_ALIGNMENT to 8 for your CPU.
Terry
On 27/05/2019 06:49, [email protected] wrote:
Hi, Terry. Thanks for your reply.
The memory alignment I set in lwipopts.h is 4 as follows. Since I am
using a 32 bit processor.
#define MEM_ALIGNMENT 4
On 05/27/2019 13:16, Terry Barnaby <mailto:[email protected]> wrote:
In your lwipopts.h what have you set for MEM_ALIGNMENT ?
// MEM_ALIGNMENT: should be set to the alignment of the CPU for
which lwIP is compiled.
#define MEM_ALIGNMENT 4
Terry
On 27/05/2019 04:17, [email protected] wrote:
Could anyone give me some advice？
I recently use mem_alloc() to allocate a structure memory which
have a int64 member. However, mem_alloc() returns a memory
poniter which is 4 byte aligned which cause a memory unaligned fault.
The code is as follows,
ifp=mem_alloc(sizeof(structure interface));
The structure intrface has a member flags which is int64. The
size of structure interface is 112 which is a multiple of 8 while
the address returned is 0x720ef324 which is not 8 byte aligned.
So when I want to access ifp->flags, an unaligned fault will be
triggered.
Could any give some hint?
Thanks!
Best regards,
yan
On 05/25/2019 22:19, yanhc519 <mailto:[email protected]> wrote:
Hi all.
What is the memory alignment of the pointer returned by
mem_alloc() in mem.c?
Since the only argument of mem_alloc() is size, so what
alignment will mem_alloc() choose?
In http://man7.org/linux/man-pages/man3/malloc.3.html, it
says "/The malloc() and calloc() functions return a pointer
to the allocated memory, which is suitably aligned for any
built-in type./"
Since the largest type is double or int64 which are 8 bytes,
so I guess /malloc() /in linux will choose alignment of 8 bytes.
Is this guess also applied to mem_alloc() in LwIP?
That is, does mem_alloc() in LwIP also choose alignment of 8
bytes?
Thanks!
Best regard,
yan
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