How to extern SDL_Surface array in C? -

i want extern sdl_surface array 1 function (load_level) (initialize_balls). have sdl_surface (brickim) dynamic pointer-struct defined inside of load_level function via malloc function , declared sdl_surface **brickim well. got segmentation fault when try access brickim[0]->w in initialize_balls function not in load_level function. piece of code hope me fix.

file1.c

#include <stdio.h> #include <sdl.h> sdl_surface **brickim; /*as global*/ sdl_surface* load_map(char *map_name , int tran );  void load_level(int stage){ int n; sdl_surface **brickim=( sdl_surface **)malloc(sizeof(sdl_surface)*input.n);     (n=0;n < input.n;n++){         **brickim[n]=load_map("brick1.bmp",1); /*load sdl_surfaces*/**         printf("%d\n",brickim[n]->w);  /***access succesfully (returns 100 n times)***/         } ... }} sdl_surface* load_map(char *map_name , int tran ){ sdl_surface *temp,*map; uint32 colorkey;         printf("loading bit map %s %d...\n",map_name,tran);         temp = sdl_loadbmp(map_name);         if (temp == null){                 printf("unable load bitmap: %s\n", sdl_geterror());                 sdl_freesurface(temp);                 exit(0);         }else{                 map = sdl_displayformat(temp);                 colorkey = sdl_maprgb( map -> format, 132, 0, 12);                 if ( tran==1 ) sdl_setcolorkey( map, sdl_srccolorkey, colorkey );                 sdl_freesurface(temp);         }                 return map;  } 

file2.c

#include <sdl.h> #include <stdlib.h> #include <stdio.h>  extern sdl_surface **brickim;/*brings brickim function*/  void initialize_balls() {       printf("into initialization :)\n ");     printf("%d \n",brickim[0]->w); /***returns segmentation fault***/ } 

$./kuranes loading bit map brick1.bmp 1... level image:) 100 (x10 times) initialization :) violación de segmento (`core' generado) 

everything running ok when used single sdl_surface compiled gcc need dynamically. think basic missing.

your problem seems here. declare global brickim, extern declaration finds. then, in load_level, declare local brickim variable. can declare variable same name in different scopes, global brickim not used within load_level, local 1 will. therefore, while malloc local brickim, don't ever assign global brickim - , therefore if access via extern, null , you'll segfault.

sdl_surface **brickim; /*as global*/ sdl_surface* load_map(char *map_name , int tran );  void load_level(int stage){ int n; sdl_surface **brickim=( sdl_surface **)malloc(sizeof(sdl_surface)*input.n);     (n=0;n < input.n;n++){         **brickim[n]=load_map("brick1.bmp",1); /*load sdl_surfaces*/**         printf("%d\n",brickim[n]->w);  /***access succesfully (returns 100 n times)***/         } ... }} 

edit: might want check whole allocation in general. i'm not familiar sdl_surface struct, assume it's not pointer type (it's generic struct). allocation allocating n structures, you're casting if you're allocating n pointers sdl_surface structures. don't cast malloc.

if want n sdl_surface structures, need have:

sdl_surface * brickim = malloc(sizeof(sdl_surface) * n) 

if want n pointers sdl_surface structures, need:

sdl_surface ** brickim = malloc(sizeof(sdl_surface *) * n) for( = 0; < n; i++){    // you've allocated array of pointers far, need    // allocate n structures      brickim[0] = malloc(sizeof(sdl_surface)); }