What are the limitations of C user identifiers for different compilers?

A C identifier consists of letters, numbers and underscores, and the first character must be a letter or underscore. Different compilers have very different restrictions on identifiers: GCC: supports longer identifiers, and the character set limit is loose; Visual C: the identifier length is limited to 255 characters, and the support for special characters is limited; other compilers (such as embedded systems): the restrictions are stricter, and only support ASCII character sets are supported. When writing cross-platform code, be careful to follow the identifier naming specifications to avoid problems caused by compiler differences.

To put it bluntly, the identifier of C language is the name you give to variables, functions, and structures. Different compilers have their own tempers on this name. Don’t think that just by name it is done. The pitfalls in it are enough to drink a pot of it.

In this article, let’s take a look at the strange restrictions on C language identifiers by different compilers. After reading it, you can write more standardized and compatible code to avoid inexplicable compilation errors and lose a few strands of hair.

Let’s talk about the basics first. C language identifiers are generally composed of letters, numbers and underscores, but the first character must be a letter or underscore. This is basically the iron rule that all compilers follow. As for the length limit, this is a problem. In theory, Standard C only stipulates that the identifier length is "at least" 31 characters, but in fact, many compilers will support longer identifiers. For example, GCC can support hundreds of characters, or even more, but if you really want to write such a long name, I advise you to save money, because the code readability is too poor.

Then, keywords cannot be used as identifiers, such as int , float , while , for etc. These are all words reserved by the compiler. If you use them, it will definitely report an error. As for case sensitivity, C is case sensitive, and myVar and myvar are two completely different identifiers.

Now, let's get to the point and see the differences between different compilers.

GCC, this is an old world, and the restrictions on identifiers are relatively loose. It supports longer identifiers and looser the restrictions on character sets. Generally speaking, you rarely encounter GCC's restrictions on identifier length or character sets. However, it may give warnings for some non-standard identifiers, which requires you to double-check the code.

Microsoft's Visual C compiler, this guy is more "old-fashioned". Its identifier length limit is relatively strict, and generally speaking, more than 255 characters will have problems. Moreover, it has limited support for some special characters, such as Unicode characters, which may be more troublesome to process. Therefore, it is better to use the VC compiler to give it a simple and clear name.

There are other compilers, such as those commonly used in embedded systems, which may have stricter restrictions on identifiers, and some even support only the ASCII character set. Therefore, when writing cross-platform code, you must pay attention to the naming specifications of identifiers and try to use simple and standard identifiers to avoid the code being unable to compile or run due to compiler differences.

Finally, I'll give some advice:

• Try to use concise and clear identifiers, and don't give some inconspicuous names.
• Avoid using identifiers similar to keywords to prevent conflicts.
• When writing cross-platform code, pay special attention to the identifier limitations of different compilers and try to use standard naming methods.
• Developing a good code style is more important than anything else.

Remember, writing code is like writing an article, and clear and concise is the king. Don't let those weird compiler restrictions affect your programming mood. If you practice more and summarize more, you will become a true C language master.

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