Valgrind错误m64 m32

Question

我正在尝试使用valgrind验证下面的代码文件test.c,当我制作gcc test.c -o test我得到了跟随错误

Syscall param write(buf) points to uninitialised byte(s)
==22765==    at 0x4F22870: __write_nocancel (syscall-template.S:81)
==22765==    by 0x4EB0002: _IO_file_write@@GLIBC_2.2.5 (fileops.c:1261)
==22765==    by 0x4EB14DB: _IO_do_write@@GLIBC_2.2.5 (fileops.c:538)
==22765==    by 0x4EB0D5F: _IO_file_close_it@@GLIBC_2.2.5 (fileops.c:165)
==22765==    by 0x4EA4B0F: fclose@@GLIBC_2.2.5 (iofclose.c:59)
==22765==    by 0x400986: main (in /home/grados-sanchez/git/merkle-codigos-C/test)
==22765==  Address 0x4025770 is not stack'd, malloc'd or (recently) free'd
==22765==  Uninitialised value was created by a stack allocation
==22765==    at 0x4007E2: node_write (in /home/grados-sanchez/git/merkle-codigos-C/test)

但是当我运行gcc test.c -o test然后valgrind时我没有得到任何错误.我的问题是在这种情况下valgrind会发生什么？有没有办法运行valgrind 32或64位？

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

#define id_lenght 6000
typedef unsigned char * ustring;
typedef struct {
    ustring ustr;
    int height;
    char id[id_lenght];
} node;

int validation_read(void * ptr_var, size_t sizeof_datatype, int num,
    FILE * ptr_file) {
    if (fread(ptr_var, sizeof_datatype, num, ptr_file) <= 0) {
        printf("Error reading file");
       return 1;
    }
return 0;
}

void node_read(FILE * node_ptr, node * n, int r) {
    int i;
    validation_read(n->id, sizeof(unsigned char), id_lenght, node_ptr);
    validation_read(&(n->height), sizeof(int), 1, node_ptr);
    validation_read(n->ustr, sizeof(unsigned char) * (r + 1), 1,node_ptr);
}

void node_init(node * n, int r) {
    memset(n, 0, sizeof(node));
    n->ustr = malloc((r + 1) * sizeof(unsigned char));
    memset(n->ustr, 0, (r + 1));
    n->ustr[r] = 0;
    n->height = -1;
    memset(n->id,0,id_lenght+1);
}


void node_write(FILE * node_ptr, node * n, int r) {
    int i;
    char newid[id_lenght];
    memset(newid,0,id_lenght);
    sprintf(newid,"%s",n->id);
    fwrite(newid, sizeof(char), id_lenght+1, node_ptr);
    fwrite(&(n->height), sizeof(int), 1, node_ptr);
    fwrite(n->ustr, sizeof(unsigned char) * (r + 1), 1,node_ptr);
}


void node_destroy(node * n) {
    free(n->ustr);
    n->height = -1;
}

int main(){
    FILE * ptr = fopen("juantest","w+");
    int r = 64/8;
    node in;
    node_init(&in, r);
    node_write(ptr, &in, r);
    node_destroy(&in);
    fclose(ptr);
}

编辑 但是当我尝试读取文件时会出现问题.我编辑了上面的代码.我得到错误读取fileError读取fileError读取

Answer 1

Valgrind很担心.在这一行

fwrite(newid, sizeof(char), id_lenght+1, node_ptr);

你写的数据比允许的多1个字节; 超出新临时堆栈字符串的那个.你可能会混淆写一个字符串(用一个+1终止零)和写入所用的(最大)缓冲区大小:

fwrite(newid, sizeof(char), id_length, node_ptr);

由于您要将内存内容转储到文件中,因此在使用之前清除字符串内存是正确的sprintf.你永远不知道新分配的内存里面是什么!
请注意,如果您担心数据完整性,最好使用安全变体sprintf_s,因为它可以防止您过度运行此缓冲区.