c - Expression must have pointer to struct or union error -

t variable coming error assigntime function onwards saying must have pointer struct or union type. pointers weakness, if explain, not give me answer, need fix helpful! cheers.

//my time c file #include "my_time.h" #include <stdio.h> #include <stdlib.h> #include <stdbool.h>  struct my_time_int  {     int hour;     int minute;     int second; };  void init_my_time(my_time *t) {      t=(my_time)malloc(sizeof(struct init_my_time*));  }  /*  * alter hour, minute, , second  * param h new value hour  * param m new value minute  * param s new value second */ void assigntime(my_time *t, int h, int m, int s)  {     t->hour = h;     t->minute = m;     t->second = s; } //following code t variable has red underline error saying expression must have pointer struct or union> char *tostring(my_time t) {      char *r = (char *)malloc(12 * sizeof(char));      if (t.hour >= 12) {     if (t.hour == 12)         sprintf(r, "%02d:%02d:%02d pm", 12, t.minute, t.second);     else         sprintf(r, "%02d:%02d:%02d pm", t.hour - 12, t.minute, t.second);     }     else {         if (t.hour == 0)         sprintf(r, "%02d:%02d:%02d am", 12, t.minute, t.second);         else         sprintf(r, "%02d:%02d:%02d am", t.hour, t.minute, t.second);     }      return r;  }  /*  * find printable form of time in 24 hour mode  * return string form of time in 24 hour mode printing etc. */ char *tomilstring(my_time t) {      char *s = (char *)malloc(9 * sizeof(char));      sprintf(s, "%02d:%02d:%02d", t.hour, t.minute, t.second);     return s; }  /*  * find number of seconds elapsed since midnight  * return number of seconds elapsed since midnight int */ int secssincemidnight(my_time t) { return t.second + (60 * t.minute) + (60 * 60 * t.hour); } 

header file here:

#include <stdbool.h>  struct my_time_int; typedef struct my_time_int *my_time;  void init_my_time(my_time *t); void assigntime(my_time *t, int h, int m, int s); void addtime(my_time t, double s); char *tostring(my_time t); char *tomilstring(my_time t); bool equals(my_time this, my_time that); bool my_timeinchour(my_time *t); bool my_timeincminute(my_time *t); bool my_timeincsecond(my_time *t); 

there couple of errors in code.

primarily use of pointers it's not correct in respect desired outcome. in header have line:

typedef struct my_time_int *my_time;

which declares my_timebeing pointer type struct my_time_int. in function's prototypes (and definitions too) use pointer my_time argument: my_time* t. in fact here using pointer pointer struct my_time_int.

so when try assign tusing deference arrow operator -> make mistake, because in fact assigning pointer pointer struct not plain pointer struct wish.

you should avoid using . operator on variables of type my_time because in facts pointers. should use instead arrow ->operator on them.

here proposed solution:

//my time c file #include "prova.h" #include <stdio.h> #include <stdlib.h> #include <stdbool.h>  struct my_time_int {     int hour;     int minute;     int second; };  //void init_my_time(my_time *t) my_time init_my_time() {     //t=(my_time)malloc(sizeof(struct init_my_time*));     return (my_time)malloc(sizeof(struct my_time_int)); }  /*  * alter hour, minute, , second  * param h new value hour  * param m new value minute  * param s new value second */ //void assigntime(my_time *t, int h, int m, int s)  void assigntime(my_time t, int h, int m, int s) {     t->hour = h;     t->minute = m;     t->second = s; }   //following code t variable has red underline error saying expression must             have pointer struct or union> char *tostring(my_time t) {  char *r = (char *)malloc(12 * sizeof(char));  //if (t.hour >= 12) { if(t->hour >= 12){ //if (t.hour == 12) if(t->hour == 12)     //sprintf(r, "%02d:%02d:%02d pm", 12, t.minute, t.second);     sprintf(r, "%02d:%02d:%02d pm", 12, t->minute, t->second); else     //sprintf(r, "%02d:%02d:%02d pm", t.hour - 12, t.minute, t.second);     sprintf(r, "%02d:%02d:%02d pm", t->hour - 12, t->minute, t->second); } else {     //if (t.hour == 0)     if (t->hour == 0)     //sprintf(r, "%02d:%02d:%02d am", 12, t.minute, t.second);     sprintf(r, "%02d:%02d:%02d am", 12, t->minute, t->second);     else     //sprintf(r, "%02d:%02d:%02d am", t.hour, t.minute, t.second);     sprintf(r, "%02d:%02d:%02d am", t->hour, t->minute, t->second); }  return r;  }  /*  * find printable form of time in 24 hour mode  * return string form of time in 24 hour mode printing etc. */ char *tomilstring(my_time t) {      char *s = (char *)malloc(9 * sizeof(char));      //sprintf(s, "%02d:%02d:%02d", t.hour, t.minute, t.second);         sprintf(s, "%02d:%02d:%02d", t->hour, t->minute, t->second);     return s; }  /*  * find number of seconds elapsed since midnight  * return number of seconds elapsed since midnight int */ int secssincemidnight(my_time t) { //return t.second + (60 * t.minute) + (60 * 60 * t.hour); return t->second + (60 * t->minute) + (60 * 60 * t->hour); } 

and header too:

#include <stdbool.h>  struct my_time_int; typedef struct my_time_int *my_time;  //void init_my_time(my_time *t); my_time init_my_time(); //void assigntime(my_time *t, int h, int m, int s); void assigntime(my_time t, int h, int m, int s);  //and son on removing unnecessary pointer types void addtime(my_time t, double s); char *tostring(my_time t); char *tomilstring(my_time t); bool equals(my_time this, my_time that); bool my_timeinchour(my_time t); bool my_timeincminute(my_time t); bool my_timeincsecond(my_time t); 

as can se in commented code there previous erroneous declarations , definitions.

edit

as pointed in comments, init_my_time, defined, leaks memory because allocates pointer doesn't return caller. right thing here allocate memory , return pointer memory caller. requires changing declaration , definition of init_my_time done above in code.