Is there any limit on the length of the C user identifier?

The length of C language identifiers is limited by the compiler and may only support some characters (such as the first 31). Concise and clear identifiers are required to avoid portability problems and reduce the possibility of errors.

Is there a limit on the length of the C user identifier? The answer is: Yes, but the actual limitation depends on the compiler and is not strictly stipulated by the standard.

This question seems simple, but it has hidden mystery. Many beginners think that as long as it does not exceed a certain number, such as 64 or 128. But the actual situation is much more complicated than this. The C standard only specifies the composition rules of the identifier, such as starting with a letter or an underscore, and can be followed by letters, numbers or underscores. But for length, the standard documentation is vague and usually only says "long enough".

Behind this "long enough" is the difference in the compiler implementation. Different compilers handle identifier lengths differently. Some compilers may only support the first 31 characters, and subsequent characters will be ignored; some compilers may support more, or even hundreds of characters. You may ask, how much is safe? There is no way to give an absolute number.

I used to use a long identifier in a project, such as process_incoming_network_data_packet_from_client_socket in order to pursue the ultimate code readability. Under the GCC compiler used at that time, everything was fine. However, when I ported the code to an embedded system and used another compiler, the problem arose: the compiler directly reported an error, saying that the identifier was too long. This makes me understand that what is called "long enough" depends entirely on the compiler.

So, what are the best practices? Don't play with fire! Don't use too long identifiers in order to pursue the so-called "expression ability". This not only brings portability problems, but also makes your code difficult to read and maintain. Remember, the code is written for people to see, and the second is executed for machines.

A clear and concise identifier is far better than a lengthy and complex identifier. For example, in the above example, you can consider splitting into multiple functions, or using shorter names such as process_network_data or even procNetData . This not only improves the readability of the code, but also reduces the possibility of errors.

For another example, the following code may be fine under some compilers, but it will report an error under other compilers, or produce unexpected results:

 <code class="c">#include <stdio.h> int incredibly_long_variable_name_that_might_cause_problems_on_some_compilers = 10; int main() { printf("%d\n", incredibly_long_variable_name_that_might_cause_problems_on_some_compilers); return 0; }</stdio.h></code>

Instead of taking this risk, it is better to develop good programming habits from the beginning and use concise and clear identifiers. This not only avoids unnecessary hassle, but also makes your code more elegant and easier to maintain. Remember, programming is not just about writing code that can run, but more importantly, writing code that is high-quality, easy to understand and maintain. This is the real way to be a big bull.

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