What does "int* p=+s;" do?
I saw a weird type of program here.
int main()
{
int s[]={3,6,9,12,18};
int* p=+s;
}
Above program tested on GCC and Clang compilers and working fine on both compilers.
I curious to know, What does int* p=+s;
do?
Is array s
decayed to pointer type?
Built-in operator+
could take pointer type as its operand, so passing the array s
to it causes array-to-pointer conversion and then the pointer int*
is returned. That means you might use +s
individually to get the pointer. (For this case it's superfluous; without operator+
it'll also decay to pointer and then assigned to p
.)
(emphasis mine)
The built-in unary plus operator returns the value of its operand. The only situation where it is not a no-op is when the operand has integral type or unscoped enumeration type, which is changed by integral promotion, e.g, it converts char to int or if the operand is subject to lvalue-to-rvalue, array-to-pointer, or function-to-pointer conversion.
Test this:
#include <stdio.h>
int main(){
char s[] = { 'h', 'e', 'l', 'l', 'o' , ' ', 'w', 'o', 'r', 'l', 'd', '!'} ;
printf("sizeof(s) : %zu, sizeof(+s) : %zu\n", sizeof(s), sizeof(+s) ) ;
}
On my PC (Ubuntu x86-64) it prints:
sizeof(s): 12, sizeof(+s) : 8
where
12 = number of elements s times size of char, or size of whole array
8 = size of pointer