[BUG] LWIP_PBUF_FROM_CUSTOM_POOLS and PBUF_POOL_SIZE don't seem to be set up in a reasonable way

[bzbarsky-apple]

Reproduction steps

LWIP_PBUF_FROM_CUSTOM_POOLS and PBUF_POOL_SIZE are used by some of our config headers (as in, its value is used in ReliableMessageProtocolConfig.h), but where are they supposed to be defined by consumers? Some things seem to have them in lwipopts.h, but our config headers don't include lwipopts.h, right?

How is this supposed to work?

Bug prevalence

Always

GitHub hash of the SDK that was being used

b02c984

Platform

other

Platform Version(s)

No response

Anything else?

No response

[rojer]

PBUF_POOL_SIZE is one of LwIP's public options hence it's ok to rely on it being defined. LwIP user code can explicitly #include <lwipopts.h>, so that seems like a valid solution (when CHIP_SYSTEM_CONFIG_USE_LWIP is set, of course).

[bzbarsky-apple]

Interestingly, we have other headers using LWIP_PBUF_FROM_CUSTOM_POOLS without obviously including lwipopts.h. But maybe those are just broken?

For now I am going to condition the use of the LwIP things on CHIP_SYSTEM_CONFIG_USE_LWIP, and then we'll see what happens when we actually try to turn on -Wundef on the LwIP-using platforms.

[rojer]

lwipopts could be transitively picked up via any other lwip include somewhere in the tree. #include "lwip/opt.h" is the first thing any lwip include does, opt.h in turn includes lwipopts.h to pick up user settings.
so actually, small correction: the right thing to do is to #include "lwip/opt.h", to make sure defaults are correctly applied.