I don't think I'd necessarily want to trap on all (signed) integer overflows. As you say, it might break working code. There's just too much C/C++ code around to change that retroactively. And for modular arithmetic and such it is desirable for integers to wrap around.

But a "trap on overflow" signed and unsigned int type would be nice.

Recent gcc versions use the fact that signed overflow is undefined to do some unexpected optimizations (in particular, a + b < a will never be true if a, b are ints.) I don't think -ftrapv is going to cause many additional errors, but I haven't actually tried it. (Also, http://embed.cs.utah.edu/ioc/ looks interesting.)

> (in particular, a + b < a will never be true if a, b are ints.)

Code of exactly that form in the patch for this bug made me do a double take. Fortunately, they'd also changed the a & b from plain ints to size_t, so it was ok.