c - 未定义对 rdtsc 的引用

Question

我正在编写创建树的代码和不同的创建树的方法。不过，我似乎无法让 rdtsc 正常运行。

这是我的代码：

    #include <stdio.h>
    #include <stdlib.h>
    #define SIZE 10
    struct tnode {
        int val;
        struct tnode *left;
        struct tnode *right;
    };
    struct tnode *addnode(struct tnode *p, long n);
    void treeprint(struct tnode *p);

    main () {
        long data[SIZE]={6, 3, 8, 1, 7, 5, 2, 9, 0, 4};
        int i;
        struct tnode *node, *root;
        unsigned long long rdtsc();
        unsigned long long a, b;

        printf("size of tnode   = %d\n", sizeof(struct tnode));
        printf("size of *node = %d\n", sizeof *node);
        printf("size of &node = %d\n", sizeof &node);
        printf("size of root = %d\n", sizeof root);
        printf("size of *root = %d\n", sizeof *root);
        printf("size of &root = %d\n", sizeof &root);

        a = rdtsc();
        root = NULL;
        for (i = 0; i < SIZE; i++)
            root = addnode(root, data[i]);
        b = rdtsc();
        treeprint(root);
        printf("It took %llu to make this tree.\n", b-a);
    }

假设上面列出的所有函数都得到了处理（当然，除了 rdtsc）。

当我尝试编译时，我收到此错误：

/tmp/cccnojMf.o: In function `main':
tree.c:(.text+0xd9): undefined reference to `rdtsc'
tree.c:(.text+0x120): undefined reference to `rdtsc'
collect2: ld returned 1 exit status

任何想法为什么我会收到这个未定义的参考错误？

Answer 1

添加它并用作函数。

 __inline__ uint64_t rdtsc(void)
   {
uint32_t lo, hi;
__asm__ __volatile__ (
        "xorl %%eax,%%eax \n        cpuid"
        ::: "%rax", "%rbx", "%rcx", "%rdx");
__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
return (uint64_t)hi << 32 | lo;
 }