c - Why does emacs show these warnings and errors? -

i trying make switch emacs vim having trouble getting syntax checkers work small c project. have tried both flymake , flycheck syntax checkers , both show non-existent compiler error. have 3 files, poker.c cards.c , cards.h.

here poker.c

#include "cards.h" #include <stdio.h> #include <stdlib.h>  int main() {    struct deck *deck = malloc(sizeof(struct deck));    struct hand *hand = malloc(sizeof(struct hand));    clear_deck(deck);   deck = init_deck(deck);   deck = shuffle(deck);   int c = deal(deck, hand);   if(c != 5) {     printf("error: not enough cards delt");   } else {     print_hand(hand);   }   return 0; } 

and cards.h

typedef enum {   two,   three,   four,   five,   six,   seven,   eight,   nine,   ten,   jack,   queen,   king,   ace, } rank;   typedef enum {   spades,   clubs,   hearts,   diamonds, } suit;  struct card {   rank rank;   suit suit;   int shuffled; };  struct deck {   struct card cards[52];   int shuffled; };  struct hand{   struct card cards[5]; };  void * shuffle(struct deck *deck); void * init_deck(struct deck *d); void clear_deck(struct deck *d); void print_deck(struct deck *d); void print_hand(struct hand *h); int deal(struct deck *deck, struct hand *hand); 

both syntax checkers show error line

  struct hand *hand = malloc(sizeof(struct hand)); 

as warnings other functions. here *flycheck errors* buffer

    9  37 error           invalid application of ‘sizeof’ incomplete type ‘struct hand’... (c/c++-gcc)    10   4 warning         implicit declaration of function ‘clear_deck’... (c/c++-gcc)    11   3 warning         implicit declaration of function ‘init_deck’... (c/c++-gcc)    11   8 warning         assignment makes pointer integer without cast... (c/c++-gcc)    12   3 warning         implicit declaration of function ‘shuffle’... (c/c++-gcc)    12   8 warning         assignment makes pointer integer without cast... (c/c++-gcc)    13   3 warning         implicit declaration of function ‘deal’... (c/c++-gcc)    17   5 warning         implicit declaration of function ‘print_hand’... (c/c++-gcc) 

i feel emacs isn't running c pre processor before doing syntax checking. there can make syntax checker work properly?

amongst other things, header file: cards.h, needs have 'include guard' suggest

#ifndef cards_h #define cards_h  typedef enum {   two,   three,   four,   five,   six,   seven,   eight,   nine,   ten,   jack,   queen,   king,   ace, } rank;   typedef enum {   spades,   clubs,   hearts,   diamonds, } suit;  struct card {   rank rank;   suit suit;   int shuffled; };  struct deck {   struct card cards[52];   int shuffled; };  struct hand{   struct card cards[5]; };  void * shuffle(struct deck *deck); void * init_deck(struct deck *d); void clear_deck(struct deck *d); void print_deck(struct deck *d); void print_hand(struct hand *h); int deal(struct deck *deck, struct hand *hand);  #endif // cards_h 

i compiled file: poker.c additions error checking.

with warnings enabled (linux ubuntu 14.04 , gcc -wall -wextra -pedantic ...)

it cleanly compiled.

here code compiled.

#include "cards.h" #include <stdio.h> #include <stdlib.h>  int main() {     struct deck *deck = malloc(sizeof(struct deck));      if( null == deck )     { // malloc failed         perror( "malloc deck failed" );         exit( exit_failure );     }      // implied else, malloc successful      struct hand *hand = malloc(sizeof(struct hand));     if( null == hand )     { // then, malloc failed         perror("malloc hand failed" );         exit( exit_failure );     }      // implied else, malloc successful      clear_deck(deck);     deck = init_deck(deck);     deck = shuffle(deck);     int c = deal(deck, hand);      if(c != 5)      {         printf("error: not enough cards delt\n"); // \n immediate output      }       else      {         print_hand(hand);     }      return 0; } // end function: main