Why Does G 4.7 Struggle with UTF-8 Characters in Identifiers Despite Extended Identifier Support?

UTF-8 Characters in Identifiers: G 's Limited Support

Despite supporting extended identifiers, G 4.7 lacks support for UTF-8 characters in identifiers. This issue arises when attempting to use Unicode characters, such as the smiley face emoji (U 1F603), which is permissible according to the C standard (Annex E.1).

Unicode Character Restrictions in G

Initially, the author tried using universal character names (Uxxxx) to represent Unicode characters. However, G rejected this approach, citing that "U0001F603" was not valid in an identifier.

Limited Functionality of -fextended-identifiers

The -fextended-identifiers option, while claiming to extend identifier support, falls short in G 4.7. It only acknowledges a narrow range of characters defined in ucnid.tab, which adheres to outdated C 98 and C99 standards.

Cross-Compiler Compatibility

As of GCC 4.9, support for the C11 character set was added. This allows for the usage of U0001F603 as an identifier. However, even with GCC 8.2, the original code using the emoji remains problematic.

In contrast, Clang 3.3 exhibits no issues with the code, even without additional options like -fextended-identifiers or -finput-charset=UTF-8.

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