分段错误,我不知道是什么导致它

Question

main.c:132:26: warning: "/*" within comment
main.c: In function ‘importSettings’:
main.c:152: warning: control reaches end of non-void function
main.c: In function ‘cs_init_missions’:
main.c:84: warning: control reaches end of non-void function
j@jonux:~/Projects/csgtk/c$ ./a.out 
Segmentation fault
j@jonux:~/Projects/csgtk/c$ 

这是使用-Wall编译并运行程序的输出.不理想.

该错误似乎涉及下面的代码.

static xmlDocPtr importSettings(char file[], GtkBuilder *builder) {
    cur = cur->xmlChildrenNode;
    while (cur != NULL) {
        if(xmlStrEqual(cur->name, (const xmlChar *) "options")) {
            cur = cur->xmlChildrenNode;
            while (cur != NULL) {
                cur = cur->next; 
            }
        }
        cur = cur->next;// <- Segfault is here
    }
}

它似乎很明显,外环尝试设置cur到cur->next时cur == NULL引起的段错误.是否有可能重建循环以避免这种情况？(我想到了一个do-while循环,但没有成功)

避免这种情况的唯一方法是将语句包含在if语句中吗？

我已经尝试过解决问题的方法.我理解为什么它首先失败了,但鉴于下面的输出它仍然失败:

static xmlDocPtr importSettings(char file[], GtkBuilder *builder){
        if (file == NULL) {
            file = "CsSettings.xml";
        }
        //commented stuff here
        settingsTree = xmlParseFile(file);
        //commented stuff here
        cur = xmlDocGetRootElement(settingsTree);
        cur = cur->xmlChildrenNode;
        while (cur != NULL){

            if(xmlStrEqual(cur->name, (const xmlChar *) "options")){ 
                cur = cur->xmlChildrenNode;
                while (cur != NULL){
        //commented stuff here
                    if(cur->next == NULL)
                        cur = cur->parent;
                    else
                        cur = cur->next;

                }
            }
            cur = cur->next;
        }
}

有什么方法可以printf()在这附近提供输出吗？即使在故障发生之前,分段故障也会以某种方式阻止其运行.

Answer 1

首先,我稍微修改了缩进并添加了一些注释.

static xmlDocPtr importSettings(char file[], GtkBuilder *builder){
    cur = cur->xmlChildrenNode;
    while (cur != NULL){
        if(xmlStrEqual(cur->name, (const xmlChar *) "options")){
            cur = cur->xmlChildrenNode;
            while (cur != NULL){
                cur = cur->next;
            }
            //at this point, cur == NULL
        }
        cur = cur->next;//seg fault here
    }
}

问题是,当if语句为真时,你运行第二个while循环,它cur等于NULL.

随后的取消引用尝试是seg错误.