blocks|key|2837032|text|您可以忽略或禁止显示警告。这是对有效的C%2B%2B指南之一的误解。指南说首选初始化而不是赋值，但在您的示例中，m_bar将被初始化。您的代码是正确的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2837033|来源:GCC的bug跟踪器中的Jonathan+Wakely：|2837034|2837035|第12项:在构造函数中首选初始化而不是赋值。替换为第4项：“确保对象在使用前已初始化”，G%2B%2B无论如何都会曲解原始项，并警告任何没有mem初始化器的成员，这非常恼人:初始化std::string是没有意义的，它有一个绝对安全的默认构造函数。我的PR2972的-Wmeminit补丁应该会替换这个项目的当前警告，因为它只警告未被构造函数初始化的成员。|blockquote|2837036|2837037|2837038|(因为这是一个已知的问题，所以没有必要再次将其报告为bug。)|2837039|entityMap|0|LINK|mutability|MUTABLE|url|http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16166#c3^0|1G|5|0|F|F|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|H|3|-4|5|6|7|14|8|@]|D|@]|E|$]]|$1|I|3|J|5|K|7|15|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|16|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|17|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|18|8|@]|D|@]|E|$]]|$1|P|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|Q|$R|$5|S|T|U|E|$V|W]]]]

You can ignore or suppress the warning. This is a misinterpretation of one of the Effective C++ guidelines. The guideline says to prefer initialisation to assignment, but in your example, <code>m_bar</code> will be initialised. Your code is correct.

Source: <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16166#c3" rel="noreferrer">Jonathan Wakely</a> in GCC's bug tracker:

<blockquote>
 # Item 12: Prefer initialization to assignment in constructors.
 
 Replaced by Item 4: "Make sure that objects are initialized before they're
 used", and G++ misinterprets the original item anyway and warns about any
 member without a mem-initializer, which is very annoying: there's no point
 initializing a std::string, it has a perfectly safe default constructor. My
 -Wmeminit patch for PR 2972 should replace the current warning for this item,
 as it only warns about members left uninitialized by the constructor.
</blockquote>

(And as it's a known issue, there's no need to report it as a bug again.)

blocks|key|2837046|text|可以忽略此警告吗？是。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2837047|忽略这个警告是个好主意吗？依赖(*)|2837048|你是不是应该把bug提交给gcc？否(*)|2837049|(*)|2837050|2837051|default构造函数实际上可以很好地初始化setting|unordered-list-item|offset|length|style|CODE|2837052|warning，你可以测试它有点奇怪，g%2B%2B没有得到你选择的|2837053|非常冗长的警告setting|2837054|warning不是关于代码的正确性，而是关于样式|2837055|你不能纠正这一点，并保留|2837056|的默认构造函数和g%2B%2B|2837057|的自定义构造函数|2837058|man+g%2B%2B，-Weffc%2B%2B节|2837059|2837060|警告违反斯科特·迈尔斯的《Effective+C%2B%2B》一书中的以下风格准则：|blockquote|2837061|2837062|2837063|2837064|第11项:为具有动态分配内存的类定义复制构造函数和赋值运算符。|2837065|第12项:在constructors.|2837066|Item+14中优先使用初始化而不是赋值。|2837067|+15:让"operator=“返回对*this的引用。|2837068|第23项:在必须返回对象时不要尝试返回引用。|2837069|2837070|同时警告违反Scott+Meyer的“More+Effective+C%2B%2B”一书中的以下风格准则：|2837071|2837072|第6项:区分递增和递减的前缀和后缀形式operators.|2837073|Item+7：|2837074|+"&&“、"││”或"，“。|2837075|2837076|2837077|选择此选项时，请注意标准库头文件并不遵守所有这些准则。|2837078|entityMap^0|0|0|0|0|0|0|7|0|0|0|0|0|0|0|0|7|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|1|1|0|0|0^^$0|@$1|2|3|4|5|6|7|20|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|21|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|22|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|23|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|24|8|@]|9|@]|A|$]]|$1|I|3|J|5|K|7|25|8|@$L|26|M|27|N|O]]|9|@]|A|$]]|$1|P|3|Q|5|K|7|28|8|@]|9|@]|A|$]]|$1|R|3|S|5|K|7|29|8|@]|9|@]|A|$]]|$1|T|3|U|5|K|7|2A|8|@]|9|@]|A|$]]|$1|V|3|W|5|K|7|2B|8|@]|9|@]|A|$]]|$1|X|3|Y|5|K|7|2C|8|@]|9|@]|A|$]]|$1|Z|3|10|5|6|7|2D|8|@]|9|@]|A|$]]|$1|11|3|12|5|6|7|2E|8|@$L|2F|M|2G|N|O]]|9|@]|A|$]]|$1|13|3|-4|5|6|7|2H|8|@]|9|@]|A|$]]|$1|14|3|15|5|16|7|2I|8|@]|9|@]|A|$]]|$1|17|3|-4|5|6|7|2J|8|@]|9|@]|A|$]]|$1|18|3|-4|5|6|7|2K|8|@]|9|@]|A|$]]|$1|19|3|-4|5|6|7|2L|8|@]|9|@]|A|$]]|$1|1A|3|1B|5|K|7|2M|8|@]|9|@]|A|$]]|$1|1C|3|1D|5|K|7|2N|8|@]|9|@]|A|$]]|$1|1E|3|1F|5|K|7|2O|8|@]|9|@]|A|$]]|$1|1G|3|1H|5|K|7|2P|8|@]|9|@]|A|$]]|$1|1I|3|1J|5|K|7|2Q|8|@]|9|@]|A|$]]|$1|1K|3|-4|5|6|7|2R|8|@]|9|@]|A|$]]|$1|1L|3|1M|5|6|7|2S|8|@]|9|@]|A|$]]|$1|1N|3|-4|5|6|7|2T|8|@]|9|@]|A|$]]|$1|1O|3|1P|5|K|7|2U|8|@]|9|@]|A|$]]|$1|1Q|3|1R|5|K|7|2V|8|@]|9|@]|A|$]]|$1|1S|3|1T|5|K|7|2W|8|@]|9|@]|A|$]]|$1|1U|3|-4|5|6|7|2X|8|@]|9|@]|A|$]]|$1|1V|3|-4|5|6|7|2Y|8|@]|9|@]|A|$]]|$1|1W|3|1X|5|6|7|2Z|8|@]|9|@]|A|$]]|$1|1Y|3|-4|5|6|7|30|8|@]|9|@]|A|$]]]|1Z|$]]

Is it alright to ignore this warning? Yes.

Is it a good idea to ignore this warning? Depends(*)

Should you file a bug to gcc? No(*)

(*)

<ul>
<li><code>default</code> constructor in fact initialises <code>m_bar</code> just fine, you can test that</li>
<li>it a bit weird that g++ doesn't get that</li>
<li>you selected very verbose warning setting</li>
<li>warning is not about correctness of your code, rather about style</li>
<li>you can't correct this and keep default constructor for Foo and custom constructor for Bar</li>
</ul>

<code>man g++</code>, section -Weffc++

<blockquote>
 Warn about violations of the following style guidelines from Scott Meyers’ Effective C++ book:
 
 <ul>
 <li>Item 11: Define a copy constructor and an assignment operator for classes with dynamically allocated memory.</li>
 <li>Item 12: Prefer initialization to assignment in constructors.</li>
 <li>Item 14: Make destructors virtual in base classes.</li>
 <li>Item 15: Have "operator=" return a reference to *this.</li>
 <li>Item 23: Don’t try to return a reference when you must return an object.</li>
 </ul>
 
 Also warn about violations of the following style guidelines from Scott Meyers’ More Effective C++ book:
 
 <ul>
 <li>Item 6: Distinguish between prefix and postfix forms of increment and decrement operators.</li>
 <li>Item 7: Never overload "&amp;&amp;", "││", or ",".</li>
 </ul>
 
 When selecting this option, be aware that the standard library headers do not obey all of these guidelines.
</blockquote>

<pre><code>struct Bar
{
 Bar() {}
};


struct Foo
{
 Foo() = default;
 Bar m_bar;
};

int main()
{
 Foo foo;
}
</code></pre>

When using C++11 <code>default</code> keyword and gcc warning <code>-Weffc++</code>, gcc outputs:

<blockquote>
 warning: ‘Foo::m_bar’ should be initialized in the member
 initialization list [-Weffc++]
</blockquote>

Is it safe to ignore this warning? Should I file a bug to gcc?

Can I ignore the gcc warning: ‘Foo::m_bar’ should be initialized in the member initialization list [-Weffc++]

struct Bar{    Bar() {}};struct Foo{    Foo() = default;    Bar m_bar;};int main(){    Foo foo;}使用C++11 default keyword和gcc warning -Weffc++时，gcc输出：警告:应在成员初始化列表...

问我能不能忽略gcc的警告：‘Foo：：m_bar’应该在成员初始化列表[-Weffc++]中初始化
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