How Well Does C 11 Actually Support Unicode?

C 11's Unicode Support

While the C 11 standard includes support for Unicode, its implementation within the standard library is limited.

Library Support

The standard library's support for Unicode is primarily through the strings library (std::string). It handles strings as sequences of char objects, providing a low-level view of text suitable for serialization and deserialization. However, it lacks direct Unicode-specific functionality.

Localization Library

The localization library relies on the assumption that a character is equivalent to a code unit. This assumption is problematic as it hinders the handling of complex characters like those in Unicode. Functions such as isspace, isprint, and iscntrl cannot accurately categorize characters with multiple code units.

Input/Output Library

The I/O library supports reading and writing Unicode text using wstring_convert and wbuffer_convert, which perform conversions between serialized (byte strings) and deserialized (wide strings) using codecvt facets. However, the standard provides limited support for Unicode encodings, primarily focusing on UTF-8, UTF-16, and UCS-2.

Regular Expressions Library

C 11's regular expressions lack level 1 Unicode support, which is crucial for properly handling complex Unicode characters. This limitation affects character classes, boundary matching, and quantifiers.

Potential Problems

• Code Unit vs. Character: The C standard's inconsistent treatment of code units and characters can lead to unexpected behavior when working with Unicode.
• Encoding Dependency: The standard library does not provide mechanisms for converting between Unicode encodings, requiring additional libraries or workarounds.
• Narrow/Wide World Separation: The narrow/wide world (char/wchar_t) remains separate from the Unicode world, with limited options for converting between the two.

Alternatives

For more comprehensive Unicode support in C , libraries like ICU and Boost.Locale offer additional functionality such as normalization, text segmentation, and improved regular expression handling.

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