CODEWITHSUNDEEP
cgcccompiler-errorsinitializerscalar
Pierre MARTY
Pierre MARTY

Reputation: 35

GCC compilation error, braces around scalar initializer [-Werror]

I'm new in C programming and I try to create a struct containing a char and a function pointer, and that is the problem.

I want to change that code:

switch (flag) {
    case 'd':
    case 'i':
    return (my_put_nbr(va_arg(ap, int)));
    case 'p':
    return (my_putstr("0x") + my_l_base_changer(va_arg(ap, char *),
    16));
    case 'u':
    return (my_put_unbr(va_arg(ap, unsigned int)));
    case 'b':
    return (my_u_base_changer(va_arg(ap, unsigned int), 2, 0));
    case 'o':
    return (my_u_base_changer(va_arg(ap, unsigned int), 8, 0));
    case 'x':
    return (my_u_base_changer(va_arg(ap, unsigned int), 16, 0));
    case 'X':
    return (my_u_base_changer(va_arg(ap, unsigned int), 16, 1));
    default:
    return (0);
}

in that kind of code:

typedef struct fptr
{
   char op;
   int (*ptr)(va_list);
} fptr;

fptr  fptrs[]=
{
   { 's', ft_print_nb_spec },
   { 'S', ft_print_nb_up },
   { 0, NULL }
};
  int i = 0;
  while (fptrs[i++].op != flag && fptrs[i].op != 0);
  if (fptrs[i].op != 0)
  {
     fptrs[i].ptr();
  }

And my struct contain a function pointer to functions who get differents prototypes

My struct is like that :

typedef struct action {
    char flag;
    void *function;
} action;

And my code who bug like that :

action registers[] = {
    { 'd', (int *)(*my_put_nbr)(int) },
    { 'i', (int)(*my_put_nbr)(va_arg(ap, int)) },
    { 'p', (int)(*my_print_ptr)(va_list ap) },
    { 'u', (int)(*my_put_unbr)(va_arg(ap, unsigned int)) },
    { 'b', (int)(*my_u_base_changer)(va_arg(ap, unsigned int), 2, 0) },
    { 'o', (int)(*my_u_base_changer)(va_arg(ap, unsigned int), 8, 0) },
    { 'x', (int)(*my_u_base_changer)(va_arg(ap, unsigned int), 8, 0) },
    { 'X', (int)(*my_u_base_changer)(va_arg(ap, unsigned int), 8, 1) },
    { 0, NULL }
};

And when I run gcc got that:

flag_nbr.c:13:28: error: expected expression before ‘int’
{ 'd', (int)(my_put_nbr)(int) },
                         ^~~
flag_nbr.c:13:28: error: missing initializer for field ‘function’ of ‘printf_action {aka struct <anonymous>}’ [-Werror=missing-field-initializers]
In file included from flag_nbr.c:8:0:
../include/my.h:21:8: note: ‘function’ declared here
void *function;
      ^~~~~~~~
flag_nbr.c:14:10: error: initialization makes pointer from integer without a cast [-Werror=int-conversion]
{ 'i', (int)(my_put_nbr)(va_arg(ap, int)) },
        ^

And I don't understand that error...

Upvotes: 0

Views: 1407

Answers (2)

Prawin
Prawin

Reputation: 61

You're using typedef to give a name to structure which already has the same name,check that. This may not be the main cause.

Upvotes: 0

Sourav Ghosh
Sourav Ghosh

Reputation: 134316

When in doubt, check the data types!!

You define the variable as an array of pointers to the action type.

What you pass in the initializers are the brace enclosed list which is certainly no match for a pointer to the action type.

In other words, you try to pass a brace enclosed list while a pointer was expected. Now, an initializer for a pointer is supposed to be a singular value (or scalar, as you may call it), so a brace enclosure is not MANDATORY.

While this is perfectly valid, most of the times, this may be caused by an issue where you write something you did not intend to write (example: your case!!) and thus, gcc produces a warning for this.

You may want to change your array type to hold structures of type action, not pointers to them.

Upvotes: 2

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