Default configuration does not permit max-size SB message buffer to be allocated

[jphickey]

Describe the bug
All messages need to be wrapped in a software bus message descriptor while in transit, and the software bus should be capable of accepting + passing messages up to CFE_MISSION_SB_MAX_SB_MSG_SIZE (configurable).

However, the default pool configuration does not allow this. Calling CFE_SB_AllocateMessageBuffer(CFE_MISSION_SB_MAX_SB_MSG_SIZE) retuns NULL due to this.

To Reproduce
Build with default configuration, and call CFE_SB_AllocateMessageBuffer(CFE_MISSION_SB_MAX_SB_MSG_SIZE) - returns NULL.

Expected behavior
Should return non-NULL, as CFE_MISSION_SB_MAX_SB_MSG_SIZE is the upper limit that should be acceptable.

System observed on:
Ubuntu

Additional context
This is because in the default SB pool configuration, there is not enough extra space in the maximum size pool block. It is defined here:

cFE/cmake/sample_defs/cpu1_platform_cfg.h

Line 305 in eb9c523

#define CFE_PLATFORM_SB_MAX_BLOCK_SIZE (CFE_MISSION_SB_MAX_SB_MSG_SIZE + 40)

The hardcoded "+ 40" bytes is not quite enough for the descriptor on a 64-bit CPU (it might work on 32-bit, did not test)

Reporter Info
Joseph Hickey, Vantage Systems, Inc.