Require exact-width integer type interfaces
Résumé
C23 already simplifies the integer model in two important aspects. First, it only has two’s complement as the sign representation of integer types and, second, we also do not allow sign bits to be masked out for a corresponding unsigned integer type. So we have gained guarantees for the homogeneity of integer representations and for the absence of padding in a general framework.
The demand for integer types with 128 and 256 bits is increasing, other languages start to have them among their required types. We should not wait another normalization cycle (12 years so far) to make this happen. Thus we propose to allow such extended types in a restricted setting, namely where they are such that they can be interfaced as exact-width integer type.
