printf - 访问冲突读取位置 - C++ [英] Printf - access violation reading location - C++
问题描述
0xC0000005:访问冲突读取位置 0xcccccccc.
0xC0000005: Access violation reading location 0xcccccccc.
printf 正在抛出这个异常.
printf is throwing this exception.
我不知道为什么会发生这种情况...这些字符串变量中有值.我使用 printf 错了吗?
I don't know why this is happening... There are values in those string variables. Am I using printf wrong?
帮助!(请看开关盒)
string header;
string body;
string key;
if (!contactList.isEmpty()) {
cout << "Enter contact's name: ";
getline(cin, key);
Contact * tempContact = contactList.get(key);
if (tempContact != NULL) {
string name = tempContact->getName();
string number = tempContact->getNumber();
string email = tempContact->getEmail();
string address = tempContact->getAddress();
//I've just put this here just to test if the variables are being initialized
cout << name + " " + number + " " + email + " " + address << endl;
switch (type) {
case 1:
printf("%-15s %-10s %-15s %-15s\n", "Name", "Number", "Email", "Address");
printf("%-15s %-10s %-15s %-15s\n", name, number, email, address);
break;
case 2:
printf("%-15s %-10s\n", "Name", "Number");
printf("%-15s %-10s\n", name, number);
break;
case 3:
printf("%-15s %-15s\n", "Name", "Email");
printf("%-15s %-15s\n", name, email);
break;
case 4:
printf("%-15s %-15s\n", "Name", "Address");
printf("%-15s %-15s\n", name, address);
break;
default:
printf("%-15s %-10s %-15s %-15s\n", "Name", "Number", "Email", "Address");
printf("%-15s %-10s %-15s %-15s\n", name, number, email, address);
}
} else {
cout << "\"" + key + "\" not found.\n" << endl;
wait();
}
} else {
cout << "Contact list is empty.\n" << endl;
wait();
}
第一个 printf 打印正常,但第二个会抛出异常,似乎不管我如何传入字符串值.
The first printf is printing fine but the second one will throw the exception, seemingly regardless of how I pass the string value in.
推荐答案
printf 的 "%s" 需要 char*
作为参数,而不是 std::string
.因此 printf 会将您的字符串对象解释为指针并尝试访问由对象的第一个 sizeof(char*)
字节给出的内存位置,这会导致访问冲突,因为这些字节并不是真正的指针.
printf's "%s" expects a char*
as an argument, not a std::string
. So printf will interpret your string objects as pointers and try to access the memory location given by the object's first sizeof(char*)
bytes, which leads to an access violation because those bytes aren't really a pointer.
要么使用字符串的c_str
方法获取char*
s,要么不使用printf.
Either use the strings' c_str
method to get char*
s or don't use printf.
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