The underlying type of the enum cannot be fixed here due to its usage
in C code.
All the values possible in the width of the underlying type are not
valid for an enum.
Only 0 to (2*max - 1) if all enumerators are unsigned.
So the macro asks for the biggest value among the //listed// ones.
If any enumerator C is set to say `A|B`, then C would be the maximum.
(2*max-1) is used as the mask.
The warnings (for each enum modified in this commit):
GPU_vertex_buffer.h:43:1: runtime error: load of value 4294967291
which is not a valid value for type 'GPUVertBufStatus'
https://github.com/llvm/llvm-project/commit/1c2c9867
Ref T81340
Reviewed By: fclem
Differential Revision: https://developer.blender.org/D9067
a31a87f894