带有指针的结构无需更改即可更改值

Question

我调试了以下程序。它找到了正确的结果，但是递归函数mmat中的ri被更改，而没有被代码pmat[q][h].ptes=NULL;和i的这一部分重新分配，最终结果是所有非预先分配的指针为null。全局变量mat **mmat遇到了同样的问题，而不是在ri中通过引用传递它。有人知道原因吗？

typedef struct tes_{
struct seg_{
    char c;
    int v;
}seg[2];
}tes;

typedef struct mat_{
    tes *ptes;
    int rot;
}    mat;

int max=0;

int main()
{
    FILE *f; char frase[M], buff[M]; int n,i,j,r,c,q=0,z=0,e=0,*pos,*esc; tes *vtes; mat **pmat, **mmat;
    printf("Inserire nome file input tessere: "); scanf("%s",frase);
    f=fopen(frase,"r");
    if (f==NULL) exit(1);
    fgets(frase,50,f); sscanf(frase,"%d",&n);
    vtes=malloc(n*sizeof(tes));
    for (i=0;i<n;i++) {fgets(frase,M,f); sscanf(frase,"%c %d %c %d",&(vtes[i].seg[0].c),&(vtes[i].seg[0].v),&(vtes[i].seg[1].c),&(vtes[i].seg[1].v));}
    fclose(f);
    printf("Inserire nome file input scacchiera: "); scanf("%s",frase);
    f=fopen(frase,"r");
    if (f==NULL) exit(1);
    fgets(frase,M,f); sscanf(frase,"%d %d",&r,&c);
    esc=(int*)malloc(r*c*sizeof(int));
    pmat=(mat **)malloc(r*sizeof(mat *));
    mmat=(mat **)malloc(r*sizeof(mat *));
    for (i=0;i<r;i++) {pmat[i]=(mat *)malloc(c*sizeof(mat));    mmat[i]=(mat *)malloc(c*sizeof(mat));}
    for (i=0;i<r;i++) {
        fgets(frase,M,f); q=0;
        for (j=0;j<c;j++) {
            z=0;
            while (frase[q]!='/') {
                buff[z]=frase[q];   q++; z++;
            }
            q++;    buff[z]='\0';    z=0;
            if (atoi(buff)==-1) pmat[i][j].ptes=NULL;
            else {pmat[i][j].ptes=&(vtes[atoi(buff)]);  esc[e]=atoi(buff);  e++;}
            while (frase[q]!=' ' || frase[q]=='\n' || frase[q]=='\0') {
                buff[z]=frase[q]; q++; z++;
            }
            q++;    buff[z]='\0';    pmat[i][j].rot=atoi(buff);
        }
    }
    pos=(int *)malloc((n-e)*sizeof(int)); q=0;
    for(i=0;i<n;i++) { // pos contiene tutte le tessere inseribili
        for (j=0;j<e;j++) if(esc[j]==i) break;
        if (j>=e) {pos[q]=i; q++;}
    }
    ri(pmat,&mmat,vtes,pos,n-e,r,c);
    printf("Max valore %d\n",max);
    for (i=0;i<r;i++) {
        for (j=0;j<c;j++) {
            printf("%c %d // %c %d\t",mmat[i][j].ptes->seg[(0+mmat[i][j].rot)%2].c,mmat[i][j].ptes->seg[(0+mmat[i][j].rot)%2].v,mmat[i][j].ptes->seg[(1+mmat[i][j].rot)%2].c,mmat[i][j].ptes->seg[(1+mmat[i][j].rot)%2].v);
        }
        printf("\n");
    }
    return 0;
}

void ri(mat **pmat, mat ***mmat, tes *vtes, int *pos, int i, int r, int c){
    int j,q,h,z,*pos2;
    if (i==0) {
        if(check(pmat,vtes,r,c)) {
                *mmat=pmat;
        }
        return;
    }
    for (j=0;j<i;j++) {
        for (q=0;q<r;q++) {
            for (h=0;h<c;h++) {
                if (pmat[q][h].ptes==NULL) break;
            }
            if (h<c) break;
        }
        if (q==r && h==c) return;
        pos2=malloc((i-1)*sizeof(int));
        for (z=0;z<i;z++){
            if (z<j) pos2[z]=pos[z];
            else if (z>j) pos2[z-1]=pos[z];
        }
        pmat[q][h].ptes=&(vtes[pos[j]]);
        pmat[q][h].rot=0;
        ri(pmat,mmat,vtes,pos2,i-1,r,c);
        pmat[q][h].rot=1;
        ri(pmat,mmat,vtes,pos2,i-1,r,c);
        free(pos2);
        if ((*mmat)[0][1].ptes==NULL) {
            printf("prob");
        }
        pmat[q][h].ptes=NULL;
        if ((*mmat)[0][1].ptes==NULL) {
            printf("prob");
        }
    }
}

int check(mat **pmat,tes *vtes, int r, int c){
    int i,j, cont=0;
    for (i=0;i<r;i++) {
        for (j=0;j<c-1;j++) {
            if (pmat[i][j].ptes->seg[(0+pmat[i][j].rot)%2].c!=pmat[i][j+1].ptes->seg[(0+pmat[i][j+1].rot)%2].c) break;
        }
        if (j==c-1) {for (j=0;j<c;j++) cont+=pmat[i][j].ptes->seg[(0+pmat[i][j].rot)%2].v;}
    }
    for (i=0;i<c;i++) {
        for (j=0;j<r-1;j++) {
            if (pmat[j][i].ptes->seg[(1+pmat[j][i].rot)%2].c!=pmat[j+1][i].ptes->seg[(1+pmat[j+1][i].rot)%2].c) break;
        }
        if (j==r-1) {for (j=0;j<r;j++) cont+=pmat[j][i].ptes->seg[(1+pmat[j][i].rot)%2].v;}
    }
    if (cont>max) {
        max=cont;
        return 1;
    }
    return 0;
}