“此处使用时变量可能未初始化”Xcode 编译器警告
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"Variable may be uninitialized when used here" Xcode compiler warning
提问by Abdelrahman Eid
So I wrote this little programthat gives this warning despite the fact that I have the variable initialized, not a duplicate question.
所以我写了这个小程序，尽管我已经初始化了变量，而不是一个重复的问题，但它给出了这个警告。
int main(int argc, const char * argv[]) {
@autoreleasepool {
int num1, num2, product, largestProduct = 0;
while (num2 < 1000) {
while (num1 < 1000) {
product = num1 * num2;
if (isPalindrome(product)) {
largestProduct = product>largestProduct?product:largestProduct;
}
num1++;
}
num1 = 0; //If I delete that line the warning disappears.
num2++;
}
NSLog(@"%i", largestProduct);
}
return 0;
}
The weird thing is if I delete that commented line the warning disappears, and if I initialize num1individually it also disappears. Am I doing something wrong or is that a bug in Xcode?
奇怪的是，如果我删除该注释行，警告就会消失，如果我num1单独初始化，它也会消失。我做错了什么还是Xcode中的错误？
回答by rmaddy
The line
线
int num1, num2, product, largestProduct = 0;
only initializes largestProductto 0. None of the other variables on that line are explicitly initialized.
仅初始化largestProduct为0. 该行上的其他变量均未显式初始化。
It's arguably poor practice to declare multiple variables on one line.
在一行上声明多个变量可以说是一种糟糕的做法。
I would suggest:
我会建议：
int num1 = 0;
int num2 = 0;
int product = 0;
int largestProduct = 0;
This is easier to read and debug.
这更易于阅读和调试。
But if you really want one line, do:
但是，如果您真的想要一行，请执行以下操作：
int num1 = 0, num2 = 0, product = 0, largestProduct = 0;
回答by Ayush Goel
In addition to @rmaddy's answer, you could also move the line num1 = 0above the second while loop. That way, when you actually use the variable num, it would have an explicit initialisation value.
除了@rmaddy 的回答之外，您还可以将行移动num1 = 0到第二个 while 循环上方。这样，当您实际使用变量时num，它将具有显式初始化值。
int main(int argc, const char * argv[]) {
@autoreleasepool {
int num1, num2, product, largestProduct = 0;
while (num2 < 1000) {
num1 = 0; //Value initialised here.
while (num1 < 1000) {
product = num1 * num2;
if (isPalindrome(product)) {
largestProduct = product>largestProduct?product:largestProduct;
}
num1++;
}
num2++;
}
NSLog(@"%i", largestProduct);
}
return 0;
}
