Question

#include <stdio.h>

#define MAX 1000000

int dp[MAX];
int P[MAX], C[MAX], K[MAX], child[MAX][1000], index[MAX];
int mod = 1000000007;

void dfs(int i) {
    int j = 1;
    while (j <= index[i]) {
        dfs(child[i][j]);
        if ((C[child[i][j]] == C[i]) && (K[i] - K[child[i][j]] == 1))
            dp[i] = (dp[i] % mod + dp[child[i][j]] % mod) % mod;
        ++j;
    }
}

int main() {
    int T, N, X, i, j;
    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &N, &X);

        for (i = 0; i < N; ++i)
            index[i] = 0;

        for (i = 1; i < N; ++i) {
             scanf("%d", &P[i]);
             child[P[i]][++index[P[i]]] = i;
        }
        for (i = 0; i < N; ++i)
            scanf("%d", &C[i]);
        for (i = 0; i < N; ++i) {
            scanf("%d", &K[i]);
            if (K[i])
                dp[i] = 0;
            else
                dp[i] = 1;
        }
        dfs(0);
        for (i = 0; i < N; ++i)
            printf("%d\n", dp[i]);
    }
    return 0;
}

当我编译上面的代码时，我收到以下错误：

In function `dfs':
(.text+0xa): relocation truncated to fit: R_X86_64_32S against symbol `index' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x3b): relocation truncated to fit: R_X86_64_32S against symbol `index' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x4f): relocation truncated to fit: R_X86_64_32S against symbol `C' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x56): relocation truncated to fit: R_X86_64_32S against symbol `C' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x60): relocation truncated to fit: R_X86_64_32S against symbol `K' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x67): relocation truncated to fit: R_X86_64_32S against symbol `K' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x74): relocation truncated to fit: R_X86_64_32S against symbol `dp' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x84): relocation truncated to fit: R_X86_64_32S against symbol `dp' defined in COMMON section in /tmp/cc0VMXET.o
(.text+0x97): relocation truncated to fit: R_X86_64_32S against symbol `dp' defined in COMMON section in /tmp/cc0VMXET.o
In function `main':
(.text.startup+0x6e): relocation truncated to fit: R_X86_64_32S against symbol `index' defined in COMMON section in /tmp/cc0VMXET.o
(.text.startup+0xba): additional relocation overflows omitted from the output
error: ld returned 1 exit status

我知道这个错误是什么;它是如何发生的。我在stackoverflow中搜索过它，但我无法理解如何纠正它。有人可以告诉我如何纠正我的代码吗？

Answer 1

您可能已经对程序中定义的全局变量的大小设置了限制：仅2D阵列child的大小为4000000000字节（40亿字节）。

要么减少某些全局变量的大小，要么在开始时使用calloc()从堆中分配它们。

试试这个版本，其中从堆中分配child：

#include <stdio.h>
#include <stdlib.h>

#define MAX 1000000

int dp[MAX], P[MAX], C[MAX], K[MAX], index[MAX];
int (*child)[1000];
int mod = 1000000007;

void dfs(int i) {
    int j = 1;
    while (j <= index[i]) {
        dfs(child[i][j]);
        if ((C[child[i][j]] == C[i]) && (K[i] - K[child[i][j]] == 1))
            dp[i] = (dp[i] % mod + dp[child[i][j]] % mod) % mod;
        ++j;
    }
}

int main(void) {
    int T, N, X, i;

    child = calloc(MAX, sizeof(*child));
    if (child == NULL) {
        fprintf(stderr, "cannot allocate child array (%llu bytes)\n",
                (unsigned long long)MAX * sizeof(*child));
        return 1;
    }

    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &N, &X);

        for (i = 0; i < N; ++i)
            index[i] = 0;

        for (i = 1; i < N; ++i) {
            scanf("%d", &P[i]);
            child[P[i]][++index[P[i]]] = i;
        }
        for (i = 0; i < N; ++i)
            scanf("%d", &C[i]);
        for (i = 0; i < N; ++i) {
            scanf("%d", &K[i]);
            if (K[i])
                dp[i] = 0;
            else
                dp[i] = 1;
        }
        dfs(0);
        for (i = 0; i < N; ++i)
            printf("%d\n", dp[i]);
    }
    free(child);
    return 0;
}

注意：

您还应检查从标准输入读取的值是否与分配的尺寸（N <= MAX和P[i] < 1000）兼容。
如果分配失败，您可以减少MAX或1000。
dp[i] = (dp[i] % mod + dp[child[i][j]] % mod) % mod;可简化为dp[i] = (dp[i] + dp[child[i][j]]) % mod;

Answer 2

数组child有10^9个元素，每个元素都是4个字节，所以它的大小几乎是4GB。但是，GCC对数据段大小有限制，默认阈值为2GB。

您有两种方法可以解决此问题：

减小数组child
使用GCC选项-mcmodel=medium编译您的程序。

参考文献：

http://www.network-theory.co.uk/docs/gccintro/gccintro_65.html https://gcc.gnu.org/onlinedocs/gcc-4.2.0/gcc/i386-and-x86_002d64-Options.html

重定位错误

2 个答案: