C imlicit declaration of a function

问题

I am on Linux and gcc 4.2.3.

For the below code portion, lp_parm_talloc_string function is called implicitly and afterwards it is defined:

char *lp_parm_string(const char *servicename, const char *type, const char *option)
{
        return lp_parm_talloc_string(lp_servicenumber(servicename), type, option, NULL);
}

/* Return parametric option from a given service. Type is a part of option before ':' */
/* Parametric option has following syntax: 'Type: option = value' */
/* the returned value is talloced in lp_talloc */
char *lp_parm_talloc_string(int snum, const char *type, const char *option, const char *def)
{
        param_opt_struct *data = get_parametrics(snum, type, option);

        if (data == NULL||data->value==NULL) {
                if (def) {
                        return lp_string(def);
                } else {
                        return NULL;
                }
        }

        return lp_string(data->value);
}

For this portion the below error comes up:

param/loadparm.c:2236: error: conflicting types for 'lp_parm_talloc_string'
param/loadparm.c:2229: error: previous implicit declaration of 'lp_parm_talloc_string' was here

How to tell compiler to allow such this case?

回答1:

You need to declare your function before using it:

char *lp_parm_talloc_string(int snum, const char *type, const char *option, const char *def);

char *lp_parm_string(const char *servicename, const char *type, const char *option)
{
    return lp_parm_talloc_string(lp_servicenumber(servicename), type, option, NULL);
}

// ...and the rest of your code

Or simply change the order the two functions appear in your source.

来源：https://stackoverflow.com/questions/5272514/c-imlicit-declaration-of-a-function

标签

function

declaration

implicit