Array of structures of function pointers C

Question

I'm trying to initialize an array of structures containing pointer on function :

typedef struct struct_actioncommand {
    char *action;
    void (*command)(my_type);
} type_actioncommand;

To initialize each pointer with its function name I'm using this method :

static const type_actioncommand g_cmd_tab[] = {
    {"Action1", function1},
    {"Action2", function2},
    {"Action3", function3},
    {NULL, NULL}
};

But it doesn't work. When I try to compile with "gcc", I have the following message:

myfile.c:16:3: error: initialization from incompatible pointer type [-Werror]
{"Action1", function1},
^
myfile.c:16:3: error: (near initialization for g_cmd_tab[0].command) [-Werror]
myfile.c:17:3: error: initialization from incompatible pointer type [-Werror]
{"Action2", function2},
^
myfile.c:17:3: error: (near initialization for g_cmd_tab[1].command) [-Werror]
myfile.c:18:3: error: initialization from incompatible pointer type [-Werror]
{"Action3", function3},
^
myfile.c:18:3: error: (near initialization for g_cmd_tab[2].command) [-Werror]
cc1: all warnings being treated as errors

each function is defined according to this prototype :

void function1(my_type *var1);

I'm a little bit confuse now since I dont see how to fix my problem. Any ideas?

Can you show us function1 etc.? Or at least their prototypes (declarations)? Though we would prefer a Minimal, Complete, and Verifiable Example. — Some programmer dude
– Some programmer dude, Commented Nov 8, 2017 at 17:36
What are the definitions of function1, function2, and function3? — dbush
– dbush, Commented Nov 8, 2017 at 17:36
Also, those errors looks like they come from GCC, which is usually very good with informational notes like what was expected and what was given. Did you copy-paste the full output, including such informational notes? — Some programmer dude
– Some programmer dude, Commented Nov 8, 2017 at 17:38
In the structure, the argument to command is a my_type object, but the declaration you show for function1 shows the argument being a pointer to my_type. Different, and incompatible, types. — Some programmer dude
– Some programmer dude, Commented Nov 8, 2017 at 17:44

dbush · Accepted Answer · 2017-11-08 18:00:43Z

2

In your struct, the command member:

void (*command)(my_type);

Has type "pointer to function which take a parameter of type my_type and returns void.

Your function:

void function1(my_type *var1);

Has type "function which takes a parameter of type my_type * and returns void.

The parameters of the function pointer don't match the parameters of the functions you assign to them. That makes the pointers incompatible.

To fix this, change the type of the function pointer to match the functions that are assigned to it:

void (*command)(my_type *);

answered Nov 8, 2017 at 18:00

dbush

233k27 gold badges261 silver badges334 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Array of structures of function pointers C

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related