How Do C Compilers Handle Unicode in Source Code?

Unicode in C Source Code: Exploring Encoding and Support

C provides support for Unicode, allowing developers to incorporate a wide range of non-ASCII characters into their source code. However, the encoding of C source code is complex and depends on the compiler implementation.

Standard Encoding

The C standard does not specify a specific source code encoding. Instead, it requires that all implementations support the basic source character set, which includes characters such as letters, digits, and punctuation. Implementations must also allow extended characters to be represented using universal character names (e.g., uxxxx or Uxxxxxxxx).

Unicode in Comments and Strings

Yes, you can use Unicode non-ASCII characters in comments by using universal character names. For example, the following comment contains Chinese characters:

<code class="cpp">// 奇怪的字符：â Țđ ě €€</code>

You can also use Unicode in strings by declaring them as wstrings or using the L prefix for literal strings. For instance:

<code class="cpp">wstring str = L"奇怪的字符：â Țđ ě €€";</code>

Implementation-Defined Encoding

While the standard mandates Unicode support, the mapping from physical source file characters to internal source characters is implementation-defined. The compiler uses an internal encoding to represent extended characters, and this encoding can vary between compilers.

In GCC, you can control the input character set used to represent source code characters with the -finput-charset option. For extended characters encoded in the source file, you can use universal character names or the internal encoding as specified by the -fexec-charset and -fwide-exec-charset options.

Subset of Unicode

The C standard does not specify which subset of Unicode is supported. Implementations may handle Unicode characters differently, including support for code points outside the Basic Multilingual Plane (BMP) or multi-byte character encodings. Consult the documentation for your compiler to determine the Unicode support it provides.

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