Why can't I assign a struct variable an element of an array of the same type of structs?

Question

I tried to assign a struct variable values from an array of the same type of structs using = operator, like below:

struct s {
    int dummy;
    char somechar[8];
} array_of_s[10];

void f(void)
{
    struct s a = array_of_s[0];  // this line gives me error message
}

int main(void)
{
    f();
    return 0;
}

I'm getting an error message and it says:

a value of type "struct s" cannot be used to initialize an entity of type "struct s"C/C++(144)

But if I hand over array as an argument like below it works like a charm:

struct s {
    int dummy;
    char somechar[8];
} array_of_s[10];

void f(struct s array_as_parameter[])
{
    struct s a = array_as_parameter[0];
}

int main(void)
{
    f(array_of_s);
    return 0;
}

Why is the first code illegal? Shouldn't I be able to access to external array variable and assign it?

Answer 1

I don't get it.

gcc -Wall -Wextra -o main main.c compiles just fine.

#include <stdio.h>

struct s {
    int dummy;
    char somechar[8];
} array_of_s[10] = {{123, "abc"}};

void f(void)
{
    struct s a = array_of_s[0];
    printf("%d, %s\n", a.dummy, a.somechar);
}

int main(void)
{
    f();
    return 0;
}

The output:

123, abc

On the other hand, VSCode shows me that error message too.

It is a bug, have a look at this: https://github.com/microsoft/vscode-cpptools/issues/3212

Answer 2

The clue is in the error message - you are not assigning you are initialising.

Change to :

struct s a ;
a = array_of_s[0]; 

That said I have never seen an error message like that (with C/C++(144) on the end - they are two different languages - that makes little sense). Moreover it compiles fine in GCC - what compiler (and version) are you using? Is this in fact not a compiler diagnostic but a pre-parse performed by your IDE/Editor?