Question

我收到了一些关于Unitialised值和条件跳转的Valgrind错误。这是我的Valgrind输出

==28124== Conditional jump or move depends on uninitialised value(s)
==28124==    at 0x4C2E0E9: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==28124==    by 0x400AA7: append_character (in /home/i)
==28124==    by 0x401319: refresh_address (in /home/)
==28124==    by 0x402067: main (in /home/)
==28124==  Uninitialised value was created by a heap allocation
==28124==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==28124==    by 0x4012C0: refresh_address (in /home/)
==28124==    by 0x402067: main (in /home/)
==28124== 
==28124== Conditional jump or move depends on uninitialised value(s)
==28124==    at 0x4C2E0E9: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==28124==    by 0x400AA7: append_character (in /home/)
==28124==    by 0x40134F: refresh_address (in /home/)
==28124==    by 0x402067: main (in /home/)
==28124==  Uninitialised value was created by a heap allocation
==28124==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==28124==    by 0x4012E0: refresh_address (in /home/)
==28124==    by 0x402067: main (in /home/)
==28124== 
==28124== Conditional jump or move depends on uninitialised value(s)
==28124==    at 0x400987: binary_decimal (in /home/)
==28124==    by 0x401377: refresh_address (in /home/)
==28124==    by 0x402067: main (in /home/)
==28124==  Uninitialised value was created by a heap allocation
==28124==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==28124==    by 0x4012E0: refresh_address (in /home/)
==28124==    by 0x402067: main (in /home/)

这是我的'append_character'功能。非常简单的东西。

void append_character(char* str, char ch){
    int len = strlen(str) + 1;
    str[len] = ch;
    str[len + 1] = '\0';
}

这是我的'refresh_address'功能。问题似乎出现的地方。

void refresh_address(int memLength, address_info *mem, char *address){
     int j = 0;
     mem -> numSetIndexBits = calculate_set_index_bits();
     mem -> numBlockOffsetBits = calculate_block_offset_bits();
     mem -> numTagBits = calculate_num_tag_bits(memLength, mem);
     mem -> tag = malloc(mem -> numSetIndexBits * sizeof(char) + 1);
     mem -> setIndex = malloc(mem -> numSetIndexBits * sizeof(char) + 1);

     for(j = 0; j < mem -> numTagBits; ++j){
        append_character(mem -> tag, address[j]);
     }

     while (j < (mem -> numSetIndexBits + mem -> numTagBits)) {
        append_character(mem -> setIndex, address[j]);
        j++;
     }    
     mem -> decimalIndex = binary_decimal(mem -> setIndex);
}

我想不出我做错了什么。知道是什么导致了这个吗？谢谢你的帮助！

编辑：address_info * mem在main中使用以下代码初始化，其中address_info是结构。

 while(fgets(buffer, 130, stdin)){
    if(sscanf(buffer, "%c:%d:%d", &accessTypes[i], &accessSize[i], &address[i]) != EOF) {
        memory = malloc(sizeof(address_info));
        init_address_info(memory);

        if (accessTypes[i] == 'W') {
                memory -> accessType = "W";
        }
        else {
                memory -> accessType = "R";
        }
        binary_add = binary_address(address[i]);
        mem_length = strlen(binary_add);
        memory -> numSetIndexBits = calculate_set_index_bits();
        refresh_address(mem_length, memory, binary_add); /*Calls malloc for the memory's set index and tag in this function*/
        ++i;
        free(binary_add);
        free(memory);
    }
}

Answer 1

向我跳出的一个显而易见的事情就是你为mem->tag分配内存，然后立即开始向它添加内容......但你从来没有初始化它（听起来很熟悉？）。这意味着您在传递的strlen()上呼叫char *，该mem->tag引用strlen，但它未初始化。这只是一个问题，你的setup.py调用和后续追加的字符然后一个null将超出你的堆分配是非常现实的。

Valgrind：未初始化的值是由堆分配

1 个答案: