What is the purpose of the unary plus (+) operator in C?

Question

In C, it\'s legal to write something like:

int foo = +4;

However, as far as I can tell, the unary plus (+) in +4

Answer 1

I found two things that unary + operator do is

• integer promotion
• turning lvalue into rvalue

integer promotion example:

#include 

int main(void) {

    char ch;
    short sh;
    int i;
    long l;

    printf("%d %d %d %d\n",sizeof(ch),sizeof(sh),sizeof(i),sizeof(l));
    printf("%d %d %d %d\n",sizeof(+ch),sizeof(+sh),sizeof(+i),sizeof(+l));
    return 0;
}

Typical output (on 64-bit platform):

1 2 4 8
4 4 4 8

turning lvalue into rvalue example:

int i=0,j;

j=(+i)++; // error lvalue required