Valóban, az egészek mérete nem pontosan specifikált. 64 bites Windowson a long 32 bit széles, míg 64 bites Linuxon a long 64 bit széles.
"in many programming environments on 64-bit machines, "int" variables are still 32 bits wide, but "long"s and pointers are 64 bits wide. These are described as having an LP64 data model. Another alternative is the ILP64 data model in which all three data types are 64 bits wide, and even SILP64 where "short" variables are also 64 bits wide [...] Another alternative is the LLP64 model, which maintains compatibility with 32-bit code by leaving both int and long as 32-bit."
Forrás: http://en.wikipedia.org/wiki/64-bit#64-bit_data_models