blocks|key|3043407|text|我曾经写过一个图书馆，必须遵守米斯拉的规则。我也需要动态内存，所以我想出了一个窍门：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3043408|我的库是用C编写的，但我的技巧可能对你有用。|3043409|头文件的一部分如下所示：|3043410|/*+declare+two+function+pointers+compatible+to+malloc+and+free:+*/
typedef+void+*+(*allocatorFunc)(size_t+size);
typedef+void+++(*freeFunc)+++++(void+*+data);

/*+and+let+the+library+user+pass+them+during+lib-init:+*/
int+library_init+(allocatorFunc+allocator,+freeFunc+deallocator);|code-block|syntax|javascript|3043411|在库中，我从未直接调用malloc/free。我总是使用提供的函数指针。因此，我将这个问题委托给其他人如何看待动态内存分配。|3043412|客户实际上喜欢这个解决方案。他意识到，如果没有动态内存分配，我的库将无法工作，这给了他使用预先分配的池或诸如此类的实现自己的内存方案的自由。|3043413|在C%2B%2B中，您也可以这样做，只需使用malloc函数并使用placement进行对象创建。|3043414|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|U|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|V|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I once wrote a library that had to comply to the MISRA rules. I needed dynamic memory as well, so I came up with a trick:

My lib was written in C, but my trick may work for you.

Part of the header-file looked like this:

<pre><code>/* declare two function pointers compatible to malloc and free: */
typedef void * (*allocatorFunc)(size_t size);
typedef void (*freeFunc) (void * data);

/* and let the library user pass them during lib-init: */
int library_init (allocatorFunc allocator, freeFunc deallocator);
</code></pre>

Inside the library I never called malloc/free directly. I always used the supplied function-pointers. So I delegated the problem how to the dynamic memory allocation should look like to someone else.

The customer actually liked this solution. He was aware of the fact that my library would not work without dynamic memory allocation and it gave him freedom to implement his own memory scheme using preallocated pools or whatnot.

In C++ you can do the same, just use the malloc function and do the object creation using placement new.

blocks|key|3238394|text|Student+exampleOfStudent(theAge);是一个自动变量，而不是静态变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3238395|据我所知，米斯拉规则不允许所有形式的动态记忆。这包括malloc和new+以及+std::vector+(带有默认分配器)。|BOLD|3238396|只剩下自动变量和静态变量。|3238397|如果您的系统有有限的RAM，您不想使用动态内存，因为您可能需要比可用内存更多的内存。堆碎片也是一个问题。这将阻止您编写可证明正确的代码。例如，如果使用带有自动或静态存储的变量，静态分析应用程序可以输出应用程序将使用的最大内存量。这个号码你可以对照你的系统RAM。|3238398|entityMap^0|0|X|0|Q|6|X|3|14|B|11|2|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|10|8|@]|D|@]|E|$]]|$1|K|3|L|5|6|7|11|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$]]

<code>Student exampleOfStudent(theAge);</code> is an automatic variable, not static.

As far as I remember, MISRA rules disallow all forms of dynamic memory. This includes both <code>malloc</code> and <code>new</code> and <code>std::vector</code> (with the default allocator).

You are left with only automatic variables and static variables.

If your system has a limited amount of RAM you don't want to use dynamic memory because of the risk you will ask for more memory than is available. Heap fragmentation is also an issue. This prevents you from writing provably correct code. If you use variables with automatic or static storage a static analysis application can, for instance, output the maximum amount of memory your application will use. This number you can check against your system RAM.

blocks|key|3238440|text|对于MISRA遵从性，安置-新不是一个问题，因为没有动态分配发生。可以编写库(如STL分配器)，以便引用静态分配的内存区域作为用于此目的的内存池。优点:确定性，快速。缺点:记忆效率低下。对确定性实时系统有利的权衡。所有需要的RAM必须在程序启动时存在，否则程序将无法运行。如果程序启动，则不受可用堆大小、碎片等的影响。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3238441|编写自己的分配器可能很复杂，内存不足的情况(毕竟静态内存池大小是固定的)仍然需要处理。|3238442|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

For MISRA compliance, placement-new is not a problem, as there is no dynamic allocation happening. 
A library could be written (like an STL allocator) in such a way as to reference a statically allocated memory region as it's memory pool for such a purpose. 
Advantages: deterministic, fast. 
Disadvantages: memory inefficient. 
A favorable trade off for deterministic real-time systems. 
All needed RAM has to be there at program startup, or the program won't run. 
If the program starts, it's unaffected by available heap size, fragmentation etc..

Writing ones own allocator can be complex and out-of-memory conditions (static memory pool size is fixed after all) still have to be dealt with.

blocks|key|2204556|text|该规则背后的想法并不是malloc和new，特别是不安全的，而是内存分配(通常)是一种懒散的解决方法，因为无法理解或管理程序的内存需求。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2204557|预先分配计算出的最大输入，并捕获超限。|unordered-list-item|2204558|提供包、流或其他面向行的输入管理方法。|2204559|使用另一种预先分配的数据结构来管理非均匀元素。|2204560|2204561|2204562|特别是在一个小型的、非MMU的嵌入式系统中，由于缺乏设计深度，常常导致系统不稳定，在那些奇怪的“角落情况”异常中完全崩溃。小内存，短堆栈，是一个系统杀手。|2204563|在许多策略中，有几种策略避免假设您没有无限内存，甚至在这个廉价的嵌入式系统中没有很多内存，并迫使您处理在应用程序中可能很重要的错误。|2204564|不要写你自己的malloc。|2204565|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$]]|$1|E|3|F|5|D|7|U|8|@]|9|@]|A|$]]|$1|G|3|H|5|D|7|V|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|W|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|R|$]]

The idea behind the rule is not that malloc and new, specifically, are unsafe, but that memory allocation is (usually) a lazy workaround for not understanding, or managing, the memory requirements of your program.
<ul>
<li>pre-allocating your calculated maximum input, and trapping overruns</li>
<li>providing a packet, stream, or other line-oriented means of managing input</li>
<li>use of an alternative pre-allocated data structure to manage non-uniform elements</li>
</ul>
Particularly in the context of a small, non-MMU, embedded system that lack of design depth frequently leads to an unstable system, that crashes outright in those odd, &quot;corner case&quot; exceptions. Small memory, short stack, is a system killer.
A few, of many, strategies that avoid the assumption that you do not have infinite memory, or even much memory in that inexpensive, embedded system - and force you to deal with the faults that might be important in your application.
Don't write your own malloc.

I need some clarification about c++ memory management and MISRA guidelines..

I have to implement one program that it's MISRA compatible so I have to respect a important rule: is not possible to use 'new' operator (dynamic memory heap).

In this case, for any custom object, I must use static allocation:

For example:

I have my class <code>Student</code> with a constructor <code>Student(int age)</code>.
Whenever I have to instantiate a Student object I must do it this way:

<pre><code>int theAge = 18;
Student exampleOfStudent(theAge);
</code></pre>

This creates an Student object exampleOfStudent.
In this way I do not to have to worry about I do not use destructors.
Is this correct all this?
Are there other ways to use static memory management?
Can I use in the same way std::vector or other data structure?
Can I add, for example, a Student instance (that I created as Student exampleOfStudent(theAge)) into a std::vector.

C++ memory management and Misra

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我需要一些关于c++内存管理和MISRA准则的说明。我必须实现一个与MISRA兼容的程序，所以我必须遵守一个重要的规则:不可能使用‘新’操作符(动态内存堆)。在这种情况下，对于任何自定义对象，我必须使用静态分配：例如：我的类Student有一个构造函数Student(int age)。每当我必须实例化一个Student...

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