Static char array declaration in C
Can someone explain to me why it int array[3] = {1,2,3}
works but
char array[3] = "123"
doesn't work?
He typed "123 ((" instead of "123").
The char array is said to require a different null character space, but it doesn't start at 0, so that's char array[3]
enough since it's actually 4 spaces. Where the char array actually requires 2 spaces for null and one for special character.
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int array[3] = {1,2,3}
allocates an array that can contain at most 3 integers, and you can access any of them using the following methods:
array[0]
array[1]
array[2]
Here:
char array[3] = "123"
"123"
consists of 4 bytes. Characters in a string literal are terminated with a NUL terminator. But you allocate 3 bytes and can hold 2 characters (+1 for a NUL terminator). So when you initialize the array with it, it is '\0'
not written as there is no room.
When you print this using %s
in printf
, it invokes Undefined behavior as it %s
prints everything as long as the NUL terminator. Therefore, it printf
continues to read values from invalid memory locations until '\0'
. Anything can happen when you do. You may see random garbage dumps, crashes, segmentation errors, etc. Basically, you should never rely on this behavior, even if it seemed to "work" as expected.
but doesn't start an array of 0
Yes
so
char array[3]
enough, since it is actually 4 spaces
Wrong. Valid indices for char array[3]
are
array[0]
array[1]
array[2]
access is array[3]
invalid and calls Undefined Behavior .
Fix the problem using
char array[4] = "123";
or better:
char array[] = "123";
The empty parentheses tell the compiler to determine the size of the array.
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