关于shared memory大小的问题

[reed-lau]

初步看代码，人为每一个topic对应一个shared_memory，而且大小是fixed=queue_size*first_msg_size+etc，如果msg每次数据大小不断变化，而且变化很大是不是会存不下queue_size个msg了？

[bjtulynn]

To use shared memory efficiently, we set default value according some rules related with single msg size and queue length. If msg size exceeds the existing msg block size, the pre-allocated shared memory will be re-allocated. You can find this logic at line 173-188 in source file "roscpp/src/publisher.cpp", thanks.