Another commenter suggested using LLMs, but I disagree. Having clangd emit warning squiggles for unchecked operations (like signed addition) would be a good start.
Another commenter suggested using LLMs, but I disagree. Having clangd emit warning squiggles for unchecked operations (like signed addition) would be a good start.
Dead code elimination is essential for performance, especially when using templates (this is basically what enables the fabled "zero cost abstraction" because complex template code may generate a lot of 'inactive' code which needs to be removed by the optimizer).
The actual issue is that the compiler is free to eliminate code paths after UB, but that's also not trivial to fix (and some optimizations are actually enabled by manually injecting UB (like `__builtin_unreachable()` which can make a measurable difference in the right places).
Not, that the compiler can also emit code paths before UB, as UB is a property of the whole program, not just of a single statement.
before.
enum op_t{ add, mul };
int exec(op_t op, int a, int b) {
if(op == add) { return a+b; }
if(op == mul) { return a\*b; }
}
c = exec(add, a,b);
Should be the compiler be prevented from inlining exec and constant-propagating op and removing the mul branch? What about if a and b are constants and the addition itself is optimized away?