Detecting underflow during execution
c++, compiler-construction, g++, gcc
Solution
C99/C++11 have floating point control functions (e.g. `fetestexcept`) and defined flags (including `FE_UNDERFLOW`) that should let you detect floating point underflow reasonably portably (i.e., with any compiler/library that supports these).
Though they're not as portable, gcc has an `feenableexcept` that will let you set floating point exceptions that are trapped. When one of the exceptions you've enabled fires, your program will receive a `SIGFPE` signal.
At least on most hardware, there's no equivalent for integer operations -- an underflow simply produces a 2's complement (or whatever) result and (for example) sets the the flags (e.g., carry and sign bits) to signal what happened. C99/C++11 do have some flags for things like integer overflow, but I don't believe they're nearly as widely supported.
Problem
Is there any way to detect underflow automatically during execution? Specifically I believe there should be a compiler option to generate code that checks for underflows and similar falgs right after mathematical operations that could cause them. I'm talking about the G++ compiler.