CODEWITHSUNDEEP
cstatements
Anbu.Sankar
Anbu.Sankar

Reputation: 1346

No error on statement without semicolon

     #include <stdio.h>
    int main()
    {

    int a,b;
    b=10;

    a=b--;
    printf("a=%d b=%d\n",a,b);

    a=b---           //Here why i didn't get error....???
    printf("a=%d b=%d\n",a,b);

                     //a=b---- or a=b---; //for these, i got error

    a=b--;
    printf("a=%d b=%d\n",a,b);

    }

why statement b--- doesn't show error. Can i say this is a bug...? If no, please explain what's going on internally...?

Upvotes: 1

Views: 76

Answers (3)

juanchopanza
juanchopanza

Reputation: 227418

printf returns int, so you have a syntactically valid statement*. This

a=b---
printf("a=%d b=%d\n",a,b);

is a single statement, which is exactly the same as this:

a = b-- - printf("a=%d b=%d\n",a,b);

or, for extra clarity,

a = (b--) - printf("a=%d b=%d\n", a, b);

In other words, for ints x and y, x--- y is parsed as (x--) - y.

* While syntactically valid, the statement itself is undefined behaviour, since there is a modification and a read of b without an intervening sequence point

Upvotes: 7

Vlad from Moscow
Vlad from Moscow

Reputation: 311038

Function printf has return type int.

From the C Standard

3 The printf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred.

So this statement

a=b---           //Here why i didn't get error....???
    printf("a=%d b=%d\n",a,b);

is a valid C statement. It can be rewritten for descriptive reason as

a = b-- - printf("a=%d b=%d\n",a,b);

or

int tmp = printf("a=%d b=%d\n",a,b);
a = b-- - tmp;

Take into account that the original statement has undefined behaviour because it is unspecified when the side effect of expression b-- will be applied to b. But in any case the code will be compiled.

Upvotes: 3

Sai Avinash
Sai Avinash

Reputation: 4753

a=b---           //Here why i didn't get error....???
    printf("a=%d b=%d\n",a,b);

This is a single statement and is valid since it is being teminated by semicolon.

Printf returns integer , so integer-integer which is valid opertion

//a=b---- or a=b---; //for these, i got error

Here , the above staments are syntactically incorrect as you are using only one operand for binary operator subtraction which indeed is invalid.

So , it has thrown the error. hope this clarifies a bit.

Upvotes: 2

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