C++ Tips - Part 02

My C++ Tips

Part 01

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Unevaluated context

• The expression is parsed and analyzed, but NOT executed.
• No opcode generated

int x = 10;
size_t s = sizeof(x++);
// x is still 10

• sizeof
• decltype
• typeid
• noexcept

What is noexcept?

void foo() noexcept; // guarantees no throw

bool b = noexcept(bar()); // // true if bar() guaranteed not to throw

Zero cost abstraction

• What you dont use, you dont pay for
• What you do use, you couldn’t hand code better
• Code will be slower to compile

Adding high level programming concept, do not come with run-time cost, only compile time cost.

Example:

template<typename T>
T add(T a, T b) 
{
    return a + b;
}

// with zero-cost abstractions, 
// No function call — it’s inlined.
int result = a + b;