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In general, universal character names should be avoided in identifiers unless absolutely necessary. The basic character set should suffice for almost every identifier.

Non-Compliant Code Example

This code example is noncompliant because it produces a universal character name by token concatenation.

#define assign(uc1, uc2, uc3, uc4, val) \
  uc1##uc2##uc3##uc4 = val;

int \U00010401\U00010401\U00010401\U00010402;
assign(\U00010401, \U00010401, \U00010401, \U00010402, 4);

Compliant Solution

This code solution is compliant.

#define assign(ucn, val) ucn = val;

int \U00010401\U00010401\U00010401\U00010402;
assign(\U00010401\U00010401\U00010401\U00010402, 4);

Risk Assessment

Creating a universal character name through token concatenation results in undefined behavior.

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

\[[ISO/IEC 10646-2003|AA. C References#ISO/IEC 10646-2003]\]
\[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\] Section 5.1.1.2, "Translation phases," Section 6.4.3, "Universal character names," and Section 6.10.3.3, "The ## operator"

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