[lwip-devel] [bug #48300] Private mempools allocate foreign memory

[chrysn]

Follow-up Comment #1, bug #48300 (project lwip):

The issue can be worked around by adding
`__attribute__((aligned(MEM_ALIGNMENT)))` after the u8_t of
LWIP_MEMPOOL_DECLARE -- but that's a GCC'ism, and as I only see those in cc.h
for `PACK_STRUCT_STRUCT`, I assume that the general intention is to keep such
compiler-isms there; the hard thing here (as compared to `PACK_STRUCT_STRUCT`,
which I assume is only used for saving memory) is that such a feature can't be
generally assumed to be present on all compilers.

I see three possible courses of action:

* Add an ALIGN macro which would need to be defined in all users' `cc.h` to
keep this subtle bug from resurfacing. (No falling back to ignoring the
alignment unless MEM_ALIGNMENT = 1).
* Unconditionally add MEM_ALIGNMENT bytes at the end of pools to compensate
for any possible offset.
* Do the latter conditionally if the former is not implemented.

Which would you prefer?

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