Unable to initialize second item in a union

Question

I have a union with the declaration:

union test_u
{
    int i;
    char *str;
};

I am trying trying to initialize a variable with data in the "second" field, using the code:

union test_u test = {"Sample"};  // char *, not int

On attempting to compile this, I receive the error:

file.c:72:11: warning: initialization makes integer from pointer without a cast

Is it possible to initialize the variable in the same manner I have above? Shouldn't the compiler (under C89) accept either an int to char * in the initialization?

possible duplicate of [Can a union be initialized in the declaration?](http://stackoverflow.com/questions/2148989/can-a-union-be-initialized-in-the-declaration) — Patrick, Jun 06 '12 at 22:28

score 5 · Answer 1 · answered Jun 06 '12 at 22:27

5

In C99, this is possible using designated initialisers:

union test_u test = { .str = "Sample" };

answered Jun 06 '12 at 22:27

Jack Kelly

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The syntax `str: "Sample"` is also possible in C89. (Not sure if it's a GCC extension though). – user703016 Jun 06 '12 at 22:29
@Cicada: Your syntax is an old GCC extension (obsolete since GCC 2.5, but GCC supports the C99 syntax as an extension to C89): http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html – Jack Kelly Jun 07 '12 at 07:41

score 2 · Accepted Answer · answered Jun 06 '12 at 22:33

2

With C89, only the first member of the union is initialised. So you can just change the order of variables in union:

union test_u
{
    char *str;
    int i;
};

answered Jun 06 '12 at 22:33

P.P

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Unable to initialize second item in a union

2 Answers2