Error “initializer element is not constant” when trying to initialize variable with const

Question

I get an error on line 6 (initialize my_foo to foo_init) of the following program and I\'m not sure I understand why.

typedef struct foo_t {
    int a, b, c;         


        

Answer 1

gcc 7.4.0 can not compile codes as below:

#include 
const char * const str1 = "str1";
const char * str2 = str1;
int main() {
    printf("%s - %s\n", str1, str2);
    return 0;
}

constchar.c:3:21: error: initializer element is not constant const char * str2 = str1;

In fact, a "const char *" string is not a compile-time constant, so it can't be an initializer. But a "const char * const" string is a compile-time constant, it should be able to be an initializer. I think this is a small drawback of CLang.

A function name is of course a compile-time constant.So this code works:

void func(void)
{
    printf("func\n");
}
typedef void (*func_type)(void);
func_type f = func;
int main() {
    f();
    return 0;
}