无法从 "warning: conversion to ' 解决 'int' long unsigned int'

Question

当我编译时mt19937ar.c ，一个非常标准的随机数生成器，我一直在使用它需要的一些代码时遇到问题。

In function 'init_genrand':

warning: conversion to 'long unsigned int' from 'int' may change the sign of the result

/* Period parameters */  
#define N 624
#define M 397
#define MATRIX_A 0x9908b0dfUL   /* constant vector a */
#define UPPER_MASK 0x80000000UL /* most significant w-r bits */
#define LOWER_MASK 0x7fffffffUL /* least significant r bits */

static unsigned long mt[N]; /* the array for the state vector  */
static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */

/* initializes mt[N] with a seed */
void init_genrand(unsigned long s)
{
    mt[0]= s & 0xffffffffUL;
    for (mti=1; mti<N; mti++) {
        mt[mti] = 
            (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti); 
        /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
        /* In the previous versions, MSBs of the seed affect   */
        /* only MSBs of the array mt[].                        */
        /* 2002/01/09 modified by Makoto Matsumoto             */
        mt[mti] &= 0xffffffffUL;
        /* for >32 bit machines */
    }
}

具体来说，错误在于

mt[mti] = 
            (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti);

我试过通过

mt[mti] = (long unsigned int)
            (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti); 

这确实没有意义，但我只是在尝试一些事情。这段代码来自 1997 年——估计现在有人会发现并修复它。我该如何解决这个问题？或者让我的编译器停止哭泣？

Answer 1

您需要将 mti 的类型更改为 unsigned int 或 unsigned long int

static unsigned int mti = N+1;

因为 mti 将在您给定的表达式中被提升为 unsigned long