Your idea for a coalescing overflow type has been explored in the document N2868 [0], a proposal for the C programming language. Instead of reserving a bit from

Your idea for a coalescing overflow type has been explored in the document N2868 [0], a proposal for the C programming language. Instead of reserving a bit from the integer, each integer type is associated with a checked integer type, which holds an integer alongside an overflow bit. Checked integers are opaque and can only be constructed and deconstructed via macros; as I understand it, the idea is that the compiler can use the processor's preexisting overflow flag to represent the checked integer. In particular, the operations on checked integers have the property of coalescing overflow checks that you are looking for. [0] Supplemental Integer Safety, http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2868.pdf http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2868.pdf