Suppose I have a piece of C code
while(1)
{
switch(a){
case 1:
if(b==1)
break;//first break
break;//second break
}
}
Will the second break get me to continue the while(1) loop and the first break get me to break out of the while(1) loop even though the first break is inside second break?
The order seems to be changed here on breaks. What is the C language implementation standard on this?
C 2024 6.8.7.4 says:
A
breakstatement terminates execution of the innermost enclosingswitchor iteration statement.
Therefore a break whose innermost enclosing switch or iteration statement is a switch statement terminates execution of that switch statement.
The first break statement executes only when the if condition b==1 is true and it exits the switch statement, not the while(1) loop. The second break statement also exits only the switch statement and not the while(1) loop.
So, the conclusion is that the while(1) loop will be continue running indefinitely or in infinite loop until an explicit break statement outside of the switch statement is written.
while loop also from inside the switch statement, by using a goto statement.
Both break statements are at the same "level", i.e. inside of the switch statement, so in both cases that's what gets broken out of.
Section 6.8.7.4p2 of the C standard regarding the break statement states:
A
breakstatement terminates execution of the innermost enclosingswitchor iteration statement
An iteration statement is defined as either a while, do, or for statement. An if is not an iteration statement, so it doesn't matter that one is inside the if statement and one is outside.
This also means that your while loop is an infinite loop because, the way your code is currently written, there's no method to break out of it.
break;you are hitting (which of the 2 does not matter) will break you out of theswitch, neither will break you out of the loop. Your code is an infinite loop, independently of the values ofaandb.breakstatement will only match the closest surrounding loop orswitch. Inside yourswitch, allbreakstatements will be for theswitch.break. It is a simple statement by itself with no associated body of statement or any nesting. When execution reaches it, control is transferred. The firstbreakis inside anifstatement. Both thatifstatement and the followingbreakare inside aswitch. Neitherbreakis inside the other.if(b==1) break; else break;All of which can be replaced withbreak;. The whole code can be replaced withwhile(1){}.