CFE_SB_MsgHdrSize returns size_t but still attempts to return CFE status code

[jphickey]

Describe the bug
The CFE_SB_MsgHdrSize() function returns a size_t value. Therefore, there is no provision/possibility for an error to be returned.

However, if passed a NULL argument, this still attempts to return CFE_SB_BAD_ARGUMENT which will be implicitly converted to a size_t value - which is platform-defined. Notably, since size_t is unsigned, the result is always positive (success range) and will not be correctly interpreted by the caller.

To Reproduce
Call CFE_SB_MsgHdrSize() with a NULL MsgPtr argument.

Expected behavior
This function should probably return 0 instead of CFE_SB_BAD_ARGUMENT in this case.
Cannot return CFE status codes from a function that does not return CFE_Status_t (or int32).

Code snips

cFE/modules/sb/fsw/src/cfe_sb_util.c

Lines 54 to 57 in 2afdbc1

	if (MsgPtr == NULL)
	{
	return CFE_SB_BAD_ARGUMENT;
	}

System observed on:
Ubuntu

Additional context
This line was also not being covered by the coverage test (#471) and the return type mismatch prevents this from being covered properly.

Reporter Info
Joseph Hickey, Vantage Systems, Inc.

[jphickey]

This also affects CFE_SB_GetUserDataLength()