[zeromq-dev] Very Small Messages/Manual

Martin Sustrik sustrik at 250bpm.com
Tue Jul 27 12:37:05 CEST 2010

Ben Kloosterman wrote:

>  >Agreed, but there's no way to set the MAX_VSM_SIZE at runtime. Compiler
>  >has to be aware of it.
> True , but I bet changing it is not tested either  . 
> This is more of an architecture decision  , instead of fixed size we could
> just assume the message is flexible and get the pipe to allocate the memory
> and just place the struct at the header. Instead of incrementing it by a
> constant message size you bump up the counter by the size in the message.

Think of this:

     zmq_msg_t msg;
     zmq_msg_init_size (&msg, 5);
     memcpy (zmq_msg_data (&msg), 5, "ABCDE");

Here the _compiler_ allocates the storage for the data on the stack. The 
size of the structure has to be fixed otherwise compiler won't know how 
to adjust the stack pointer.


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