Irritatingly, GCC lacks a "branch on overflow" intrinsic or "add and branch on overflow" intrinsic, forcing you to write inline asm to do fast overflow checking.
> A new set of built-in functions for arithmetics with overflow checking has been added: __builtin_add_overflow, __builtin_sub_overflow and __builtin_mul_overflow and for compatibility with clang also other variants
It's like trying to talk to Haskell about explicit thunks, or Lisp about stack-vs-heap allocation. The language encapsulates the concept away from you, so if you wrench it back, you're no longer quite writing the language; you're writing a union of it and something else.
long mega_byte = 1024 * 1024 * 8; // bits per MB long mega_bit = 1000 * 1000; // bits per megabit
If you follow the C90 standard, this code has all sorts of issues. First, // comments are not allowed. Second, identifiers are only guaranteed to have six significant characters, so the above two variables might actually be the same variable. Finally, ints are only guaranteed to be 2 bytes, so the multiplication may overflow and the program is undefined. (Assigning to longs doesn't help: the multiplication already happened.)