Hello,
according to the gnat ref. manual
http://gcc.gnu.org/onlinedocs/gnat_rm/Implementation-Defined-Characteristics.html
Standard.Interger'Size is 32 bit for the compilation target.
I'd like to know if the Ada frontend (not the runtime system) depends on this (target) setting in any way?
Yes, the front end uses Ada strings which are indexed by Integer. Integer cannot be 16 bits. The Ada RM does allow this, but I am pretty sure GNAT counts on integer being 32 bits.