c - Why is this struct passed as argument of a function, change is values? -

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i have struct , function:

typedef struct pares{ int x,y; } par;  arvpre criararvore(    int i,     int j,     char matriz[i][j],     int x,     int y,     int *c,     par vis[],     int k    )

as can see, pass par vis array of structs. i've been taught, way, value of vis declared outside function; , therefore should remain unaltered, right? example, if it's 0 before calling function, after function should still zero. however, values change after calling function.

here full code: 

typedef struct arv *arvpre;  typedef struct arv {    char valor;    arvpre n[8];    int flag; }nodo;  typedef struct pares{    int x,y; } par;  arvpre criararvore(      int i,       int j,       char matriz[i][j],       int x,       int y,       int *c,       par vis[],       int k      ) {    arvpre a=null;    int z;     while (*c){       if (x>=j || x<0 || y<0 ||y>=i || vizitado (vis,k,x,y)) {             return null;          }       else {             a=(arvpre) malloc (sizeof(nodo));             a->valor=matriz[y][x];             vis[k].x=x;              vis[k].y=y;              k++;             (*c)--;             z=*c;             a->n[0] = criararvore (i,j,matriz,x,y-1,c,vis,k);             *c=z;             a->n[1] = criararvore (i,j,matriz,x-1,y-1,c,vis,k);             *c=z;             a->n[2] = criararvore (i,j,matriz,x-1,y,c,vis,k);             *c=z;             a->n[3] = criararvore (i,j,matriz,x-1,y+1,c,vis,k);             *c=z;             a->n[4] = criararvore (i,j,matriz,x,y+1,c,vis,k);             *c=z;             a->n[5] = criararvore (i,j,matriz,x+1,y+1,c,vis,k);             *c=z;             a->n[6] = criararvore (i,j,matriz,x+1,y,c,vis,k);             *c=z;             a->n[7] = criararvore (i,j,matriz,x+1,y-1,c,vis,k);             *c=z;              return a;          }    } }  int main(){    int i,j,c, dimy=3,dimy=4, flag=0;    par vis[23];    char sopal[3][4]={{'o','r','c','a'},{'r','a','i','o'},{'a','t','n','s'}};    struct arv teste;    arvpre a;    a=&teste;    (i=0;i<dimy;i++)       (j=0;j<dimx;j++){          c=23;          (b=0;b<23;b++) printf("%d %d ",vis[b].y,vis[b].x);          printf("\n");          a=criararvore(dimy,dimx,sopal,i,j,&amp;c,vis,k);          printf("sucssess %c! \n", a->valor);          (b=0;b<23;b++) printf("%d %d ",vis[b].y,vis[b].x);          printf("\n");       }     return 0; }

the program seg-faults, array printed few times before that. changes each time called.

why this?

par vis[] in parameter list same par* vis.

any assignment through vis, vis [0].x = 1; change parameters passed in calling function.


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