Comparing int with long and others

Question

I am wondering if things like this :

int a = ...;
long b = ...;

if (a < b)
     doSomethings();

always works (excepted for unsigned)

Answer 1

In this condition

if (a < b)

an object of type int is always converted to the type long provided that one of the operands has type long because type long has higher rank than type int.

As for other types then according to the C Standard (6.5.8 Relational operators)

3 If both of the operands have arithmetic type, the usual arithmetic conversions are performed.

It means that after the integer promotion an operand with a lower rank is converted to the type of the other operand.