[lwip-users] api_lib.c MEMP_API_MSG usage

[Goldschmidt Simon]

Hi list,

 

I recently took a close look at the usage of 'struct api_msg' variables in api_lib.c. Throughout the file, those variables are allocated using the mem-pool MEMP_API_MSG. Surprisingly, I noticed that those variables are always allocated at the beginning of a function (memp_malloc()) and deallocated at the end of the same function (memp_free()). So, if the lifetime of such a variable is only for one function, why not allocate it on the stack? Although allocating through a pool is not that slow, allocating on the stack is still faster (you get it 'for free' when entering the function). Also, (on a 32-bit platform) a 'struct api_msg' should be 24 bytes max, so this is not really too big for the stack, is it?

I tested this by changing api_lib.c so all api_msg variables are allocated on the stack and it works. Any one interested in this topic?

 

Simon