Shared memory and IPC

Luke Kenneth Casson Leighton lkcl at
Fri Sep 7 03:06:01 GMT 2001


as and when you get to this, you're probably going to
need some shared-memory management ... 'stuff'.

for example, as you mention, a well-known shared
list of structures that describe the locations 
of other shared segments.

that being the case, it would be extremely useful
to work with sander, david, ryan, greg and justin
from APR to produce an sms_shmem, for use at least
by APR and the dcom project.

once an sms_shmem manager is available, it can
be used as the base-level on which to build the


On Fri, Sep 07, 2001 at 10:06:16AM +0100, Wez Furlong wrote:
> On 06/09/01, "John E. Malmberg" <malmberg at> wrote:
> > > > Memory allocated using the COM IMalloc must
> > > > be passable directly to another process (ie: appear at the same address),
> > > > so I think we might need a COM-wide shared memory context of some kind.
> > Is there some way that relative pointers can be used inside the shared
> > memory, and the functions that access the pointers know what the base
> > address is?
> Yes (as others have discussed), but for the purposes of the COM MEMCTX_SHARED
> IMalloc, if we implement it at all, it must work such that the allocated
> pointer works in all address spaces (because it could be passed anywhere!).
> Now, if the person using it is stupid enough to put a pointer to somewhere
> that's not accessible inside something in that shared mem, their program
> deserves to get a sigsegv or sigbus!
> It's looking like a right PITA, so I'm moving it down on my todo list.
> However, using shared memory to speed up marshalling seems like a good way to
> go (performance wise); it's staying at about the same place on my todo :)
> --Wez.
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