Bill Auerbach schrieb:
Bill Auerbach wrote:
One problem however: If I define LWIP_CHKSUM in my sys_arch.h,
inet_chksum.c doesn't know about it. I had to add #include
"sys_arch.h" to inet_chksum.c. In order to override LWIP_CHKSUM
without changing source code, shouldn't include sys_arch.h?
I don't think so: sys_arch.h is supposed to provide things needed for
the sys layer (like threads, mboxes and semaphores). When compiling with
NO_SYS=1, the whole stack should still be compilable without the whole
sys_arch.h file. You will have to put the definition somewhere else.
OK. I see. This define (LWIP_CHKSUM) belongs in lwipopts.h not sys_arch.h
as per the comment. The question becomes where to put the prototype for the
replacement function. If it's in sys_arch.h to match sys_arch.c where the
function definition is, then lwipopts.h or inet_chksum.c need sys_arch.h
added to get the prototype pulled in.
In my opinion, the comment is wrong. Also the place you want to put it
seems wrong. The files sys_arch.c and sys_arch.h are supposed to be an
architecture-dependent extension for sys.c. And sys.c's purpose is to
provide OS abstraction functions. Like you already stated, the
LWIP_CHKSUM function is needed regardless of the NO_SYS setting (in
fact, that's what I meant in my last mail) so you have to put it
somwhere else, not in sys_arch.c: sys.c and sys_arch.c don't have to be
included in your build when compiling with NO_SYS=1!
You can just put the definition into cc.h or lwipopts.h and create your
own c file with the function in it. And perhaps we should include an
example in the contrib folder to clarify this for the future...?
Simon
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