Question

我最近从windows上的dev c ++切换到osx dev环境，并尝试使用sublime文本3.但是，当我运行程序时，我遇到了分段错误。以下是错误消息：

/bin/bash: line 1: 20506 Segmentation fault: 11  "/Users/jimi/Documents/University/lab0603"
[Finished in 1.2s with exit code 139]
[shell_cmd: g++ "/Users/jimi/Documents/University/lab0603.cpp" -o "/Users/jimi/Documents/University/lab0603" && "/Users/jimi/Documents/University/lab0603"]
[dir: /Users/jimi/Documents/University]
[path: /usr/bin:/bin:/usr/sbin:/sbin]

以下是完整代码：

#include <iostream>
#include <cmath>

using namespace std;


string flightDirections[16] = {"ENE", "NE", "NNE", "N", "NNW", "NW", "WNW", "W", "WSW", "SW", "SWS", "S", "SSE", "SE", "ESE", "E"};
double cruisingSpeed = 0;
double windSpeed = 0;
int windDirection = 0;
double flightDistance = 0;

string numberToDirection(int direction) {

    return (direction) ? "The wind is blowing from the East." : " The wind is blowing from the West.";

    //this way we only have one return statement :)

}

void getInput () {
    cout << "Hello! \n"
         << "Thank you for choosing to use this really great program!! \n"
         << "This program will compute the necessary heading adjustment for your flight,"
         << " and provide the estimated flight time. \n";
    cout << "Enter the aircraft cruising speed in still air (in km/h): ";
    cin >> cruisingSpeed;
    cout << " \n \t cruising speed = " << cruisingSpeed << "\n Enter the wind speed in km/h: ";
    cin >>  windSpeed;
    cout << " \n \t wind speed = " << windSpeed << "\n Enter 1 if the wind is blowing from the West and -1 if wind is blowing from the East:";
    cin >> windDirection;
    cout << "\n\t" << numberToDirection(windDirection) << "\n Enter the distance between the originating and destination cities, in km:";
    cin >> flightDistance;
    cout << "\n\t flight distance = " << flightDistance << "\n Enter the compass direction of the destination city, relative to the originating cities, using the following values:";
    for (int i = 0; i < sizeof(flightDirections); i++) {
        cout << i + 1;
        cout << flightDirections[i];
    }
    cin.ignore();


}

int main() {


    getInput();
    return 0;

}

发生了什么事？

Answer 1

问题在于您的for循环。

for (int i = 0; i < sizeof(flightDirections); i++)

当sizeof(flightDirections)比数组的大小更大时，将从数组的末尾开始运行。 sizeof(flightDirections)是sizeof(std::string) * number_of_elements_in_the_array。为了获得正确的数组大小，您需要使用

sizeof(flightDirections) / sizeof(flightDirections[0])

或者更好地使用ranged based for loop作为

int i = 0;
for (const auto & e : flightDirections) {
    cout << ++i << e;
}

Answer 2

您错误地使用了sizeof。 sizeof返回实体包含的 bytes 的数量，而不是条目的数量（对于数组的情况）。因此，这是不正确的：

 for (int i = 0; i < sizeof(flightDirections); i++) {

你应该只是使用：

for (int i = 0; i < sizeof(flightDirections)/sizeof(flightDirections[0]); i++) {

Answer 3

sizeof给出大小（以字节为单位），而不是数组的元素数。当你打电话给sizeof(flightDirections)时，你可能会期待16，但恐惧更多。因此，你的循环走得太远，超出了数组的索引，并且你得到了未定义的行为 - 在这种情况下，是一个分段错误。

由于您已经对数组的大小进行了硬编码，因此您甚至可以对循环进行硬编码。或者，如果您想拥有更灵活的代码，您可以通过将sizeof（flightDirections）的重新除以单个元素的大小来计算元素的数量，如下所示：

for (int i = 0; i < sizeof(flightDirections)/sizeof(flightDirections[0]); i++) {

（这个技巧在C中是常见的做法，当你必须将一个数组传递给一个函数时：由于数组会失去它的大小（当它传递给它时衰减到一个指针），你必须明确地传递它，作为第二个参数，这是正常的做法。）

Answer 4

如果要使用sizeof（）来查找数组的长度，则需要将其除以数组中保存的内容。看到这个问题：

How do I find the length of an array?

你可以使用std :: vector吗？这有一个size（）方法。

sublime text C ++编译导致seg错误

4 个答案: