blocks|key|1211990|text|这是一个很长的列表。最好的做法是阅读示例。例如，source+of+perl。如果您查看perl的源代码，您将看到一个庞大的构建头文件的过程，该文件处理大约50个平台问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1211991|读一读，哭一哭，或者借一借。|1211992|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cpan.org/src/^0|O|E|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

It is a very long list. The best thing to do is to read examples. The <a href="http://www.cpan.org/src/" rel="nofollow noreferrer">source of perl</a>, for example. If you look at the source of perl, you will see a gigantic process of constructing a header file that deals with about 50 platform issues.

Read it and weep, or borrow.

blocks|key|1212049|text|这个列表可能很长，但它并不像支持Windows和MSDOS那样长。这在许多实用程序中都很常见。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1212050|通常的技术是将核心算法模块与处理操作系统的模块分开--基本上是一种分层抽象的策略。|1212051|相比较而言，区分几种不同风格的unix相当简单。要么坚持所有功能都使用相同的RTL名称，要么查看支持的平台和例外中的#ifdef的大多数约定。|offset|length|style|CODE|1212052|entityMap^0|0|0|1M|6|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|N|8|@$F|O|G|P|H|I]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

The list may be long, but it's not nearly as long as also supporting Windows and MSDOS. Which is common with many utilities.

The usual technique is to separate core algorithm modules from those which deal with the operating system—basically a strategy of layered abstraction.

Differentiating amongst several flavors of unix is rather simple in comparison. Either stick to features all use the same RTL names for, or look at the majority convention for the platforms supported and <code>#ifdef</code> in the exceptions.

blocks|key|125703|text|我能给出的最好的建议是，每天移动到一个不同的平台，边走边测试。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|125704|这将使平台的差异像一个疼痛的拇指一样突出，同时也会教你可移植性问题。|125705|把跨平台测试留到最后，会导致测试失败。|125706|抛开这个不谈|125707|differently.|125708|integers+endianism.|unordered-list-item|125709|
|125710|Compilation整数大小可能不同。|125711|浮点数可以表示为不同的|125712|选项。|125713|125714|包含的文件名可能不同。|125715|位字段的实现也会有所不同。|125716|125717|125718|通常，将编译器的警告级别设置得尽可能高是个好主意，以查看编译器可能会抱怨的内容。|125719|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|16|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|17|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|18|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|19|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|1A|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1B|8|@]|9|@]|A|$]]|$1|O|3|P|5|L|7|1C|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|1D|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1E|8|@]|9|@]|A|$]]|$1|U|3|-4|5|L|7|1F|8|@]|9|@]|A|$]]|$1|V|3|W|5|L|7|1G|8|@]|9|@]|A|$]]|$1|X|3|Y|5|L|7|1H|8|@]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]|$1|11|3|12|5|6|7|1K|8|@]|9|@]|A|$]]|$1|13|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]]|14|$]]

The best advice I can give, is to move to a different platform every day, testing as you go. 
This will make the platform differences stick out like a sore thumb, and teach you the portability issues at the same time.

Saving the cross platform testing for the end, will lead to failure.

That aside

<ul>
<li>Integer sizes can vary.</li>
<li>floating point numbers might be represented differently.</li>
<li>integers can have different endianism.</li>
<li>Compilation options can vary.</li>
<li>include file names can vary.</li>
<li>bit field implementations will vary.</li>
</ul>

It is generally a good idea to set your compiler warning level up as high as possible,
to see the sorts of things the compiler can complain about.

blocks|key|870772|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|870773|至少使用两个适当的持续构建系统，最好是构建在各种目标平台上。|ordered-list-item|870774|如果您不需要非常底层的工作，请尝试使用一些提供抽象的库。您不太可能找不到为您需要的东西提供良好抽象的第三方库。例如，对于网络和通信，有ACE。Boost+(例如文件系统)也可以移植到多个平台上。这些都是C%2B%2B库，但也可能有其他的C库(如curl)。|870775|如果您必须在低级工作，请注意，即使在posix这样的平台上，平台有时也会有不同的行为，因为它们应该具有相同的行为。你可以看看上面这些库的源代码。|870776|870777|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|K|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|L|7|@]|8|@]|9|$]]|$1|D|3|E|4|C|6|M|7|@]|8|@]|9|$]]|$1|F|3|G|4|C|6|N|7|@]|8|@]|9|$]]|$1|H|3|-4|4|5|6|O|7|@]|8|@]|9|$]]|$1|I|3|-4|4|5|6|P|7|@]|8|@]|9|$]]]|J|$]]

<ol>
<li>Use atleast two compilers.</li>
<li>Have a continuous build system in place, which preferably builds on the various target platforms. </li>
<li>If you do not need to work very low-level, try to use some library that provides abstraction. It is unlikely that you won't find third-party libraries that provide good abstraction for the things you need. For example, for network and communication, there is ACE. Boost (e.g. filesystem) is also ported to several platforms. These are C++ libraries, but there may be other C libraries too (like curl). </li>
<li>If you have to work at the low level, be aware that the platforms occasionally have different behavior even on things like posix where they are supposed to have the same behavior. You can have a look at the source code of the libraries above. </li>
</ol>

blocks|key|2621591|text|您可能需要与之保持同步的一个特殊问题是endianness+(例如，如果您的数据文件希望跨平台工作)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2621592|在不同的体系结构上，数字在二进制级别上以不同的方式表示。大端系统将最高有效字节排在第一位，小端系统将最低有效字节排在第一位。|2621593|如果您以一种字节序将一些原始数据写入文件，然后在另一种字节序的系统上读回该文件，那么您显然会遇到问题。|2621594|在大多数系统上，您应该能够在编译时从sys/param.h获得字节顺序。如果需要在运行时检测它，一种方法是使用int和char的联合，然后将char设置为1，并查看int的值是什么。|style|CODE|2621595|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Endianness^0|J|A|0|0|0|0|I|B|1J|3|1N|4|1Y|4|2A|3|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|Z|8|@$A|10|B|11|J|K]|$A|12|B|13|J|K]|$A|14|B|15|J|K]|$A|16|B|17|J|K]|$A|18|B|19|J|K]]|9|@]|C|$]]|$1|L|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]]]

One particular issue that you may need to stay abreast of (for instance, if your data files are expected to work across platforms) is <a href="http://en.wikipedia.org/wiki/Endianness" rel="nofollow noreferrer">endianness</a>.

Numbers are represented differently at the binary level on different architectures. Big-endian systems order the most significant byte first and little-endian systems order the least-significant byte first.

If you write some raw data to a file in one endianness and then read that file back on a system with a different endianness you will obviously have issues.

You should be able to get the endianness at compile-time on most systems from <code>sys/param.h</code>. If you need to detect it at runtime, one method is to use a union of an <code>int</code> and a <code>char</code>, then set the <code>char</code> to 1 and see what value the <code>int</code> has.

blocks|key|2621636|text|对于您使用的任何库函数，请继续参考POSIX标准。标准的某些部分是模棱两可的，有些系统返回不同样式的错误代码。这将帮助您主动发现那些真正难以找到细微不同的实现错误。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2621637|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Continually refer to the POSIX standards for any library functions you use. Parts of the standard are ambiguous and some systems return different styles of error codes. This will help you to proactively find those really hard to find slightly different implementation bugs.

blocks|key|124754|text|我曾经写过C实用程序，然后我会在16位到64位的体系结构上支持它们，包括一些60位的机器。它们包括至少三种不同的“字节顺序”、不同的浮点格式、不同的字符编码和不同的操作系统(尽管Unix占主导地位)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|124755|124756|尽可能接近标准C。对于不属于该标准的函数/库，请尽可能使用广泛支持的代码库。例如，对于网络，使用BSD套接字接口，使用零或最少使用低级套接字选项、带外信令等。要以最少的人员支持大量不同的平台，您将不得不使用普通的普通函数。|ordered-list-item|124757|非常了解标准所保证的内容，以及典型的实现行为。例如，指针不必与整数大小相同，并且指向不同数据类型的指针可以具有不同的长度。如果您必须进行依赖于实现的假设，请详细记录它们。在这里，Lint、--strict或您的开发工具集拥有的任何等效工具都是至关重要的，|124758|头文件是您的好朋友。使用实现定义的宏和常量。使用头文件定义和#ifdef来帮助隔离那些需要覆盖少量alternatives.|124759|Don't的实例。有相当数量的ASCII+-2的补充机也在那里。:-)|124760|124761|有了这些，如果你避免多次编写代码和#ifdef主要代码部分的诱惑，你会发现跨不同平台的编码和测试有助于更快地发现bug。您将最终生成更有纪律的、可理解的、可维护的程序。|124762|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|R|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|T|8|@]|9|@]|A|$]]|$1|H|3|I|5|E|7|U|8|@]|9|@]|A|$]]|$1|J|3|K|5|E|7|V|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|P|$]]

I used to write C utilities that I would then support on 16 bit to 64 bit architectures, including some 60 bit machines. They included at least three varieties of "endianness," different floating point formats, different character encodings, and different operating systems (though Unix predominated).

<ol>
<li>Stay as close to standard C as you can. For functions/libraries not part of the standard, use as widely supported a code base as you can find. For example, for networking, use the BSD socket interface, with zero or minimal use of low level socket options, out-of-band signalling, etc. To support a wide number of disparate platforms with minimal staff, you'll have to stay with plain vanilla functions.</li>
<li>Be very aware of what's guaranteed by the standard, vice what's typical implementation behavior. For instance, pointers are not necessarily the same size as integers, and pointers to different data types may have different lengths. If you must make implementation dependent assumptions, document them thoroghly. Lint, or --strict, or whatever your development toolset has as an equivalent, is vitally important here.</li>
<li>Header files are your friend. Use implementaton defined macros and constants. Use header definitions and #ifdef to help isolate those instances where you need to cover a small number of alternatives.</li>
<li>Don't assume the current platform uses EBCDIC characters and packed decimal integers. There are a fair number of ASCII - two's complement machines out there as well. :-)</li>
</ol>

With all that, if you avoid the tempation to write things multiple times and #ifdef major portions of code, you'll find that coding and testing across disparate platforms helps find bugs sooner. You'll end up producing more disciplined, understandable, maintainable programs.

For a project at university I need to extend an existing C application, which shall in the end run on a wide variety of commercial and non-commercial unix systems (FreeBSD, Solaris, AIX, etc.).

Which things do I have to consider when I want to write a C program which is most portable?

Writing a portable C program - which things to consider?

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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对于大学中的一个项目，我需要扩展现有的C应用程序，它最终将在各种商业和非商业unix系统(FreeBSD、Solaris、AIX等)上运行。当我想要写一个可移植性最好的C程序时，我必须考虑哪些事情？

问编写一个可移植的C程序--需要考虑哪些事情？
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问编写一个可移植的C程序--需要考虑哪些事情？EN