function returns address of local variable

char *B2G (long long b)
{  
  //static char g[10]; //value do not change
  char g[10]; //null
  //char *g; //crash
  if (b > 999999999) {
    sprintf(g, "%.2fGB", b/1073741824.0);
  } else {
    if (b > 999999) {
      sprintf(g, "%.2fMB", b/1048576.0);
    } else {
      if (b > 999) {
        sprintf(g, "%.2fKB", b/1024.0);
      } else {
        sprintf(g,"%d B", b);
      }
   }
  }
  return g;
}

B2G(m);

 局部变量用完销毁，返回空，static值不变，怎么解决？

【c/c++】function returns address of local variable_dmcler的博客-优快云博客

char *g = malloc(10);