3.5.7 How Big Can C Variables Be?

This question specifically relates to the size of individual C objects, such as arrays or structures. The total size of all variables is another matter.

To answer this question you need to know in which memory space the variable will be located.

With the default -membedded-data option, objects qualified const will be located in program memory; other objects will be placed in data memory. Program memory object sizes are discussed in Size Limitations of const Variables. Objects in data memory are broadly grouped into autos and non-autos and the size limitations of these objects, respectively, are discussed in Non-Auto Variable Allocation and Non-Auto Variable Size Limits.