I would like to point out that identifiers like "_MODBUS_H_" and "_MODBUS_TCP_H_" do not fit to the expected naming convention of the C language standard.
Would you like to adjust your selection for unique names?
Avoid to use reserved identifiers for header names (closes #157)
Not applied to libmodbus constants for now...
Thanks for the report, not sure to want to change constant names too...
Thanks for your improvement of the include guards.
I would prefer that the remaining affected identifiers will also become standard-compliant.