c - Valgrind:未初始化的值是由堆分配创建的

我得到了一些关于单位化值和条件跳跃的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“附加字符”函数。很简单的东西。

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

这是我的“刷新地址”功能。出现问题的地方。

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。知道是什么原因吗？谢谢你的帮助！
编辑：address_info*mem在main中初始化，代码如下，其中address_info是一个结构。

 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);
    }
}

最佳答案

我突然想到的一件显而易见的事情是，您为mem->tag分配内存，然后立即开始向它追加内容。。。但你从未初始化过它（听起来很熟悉？）。这意味着您正在传入的strlen()上调用char *，它指的是mem->tag，但未初始化。这只是自找麻烦，而且非常现实的是，您的strlen调用和随后的字符附加，然后一个空值将超出您的堆分配。

关于c - Valgrind:未初始化的值是由堆分配创建的，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/34101845/