Why Were Designated Initializers Excluded from C 11?

Designated Initializers in C 11: Rationale for Exclusion

While C99 allows the use of designated initializer lists, such as in the code snippet provided, C 11 prohibits this feature. This decision by the C 11 standard committee raises the question of why such a convenient feature was excluded.

C.1.7[diff.decl].4: Restrictions in C :

Introducing designated initializers in C would have posed several challenges:

• Indeterminate Evaluation Order: In C99, the order of evaluation for designated initializers is unspecified, leading to potential undefined behavior if the initialized members interact. In contrast, C enforces a strict evaluation order for initializer lists, preventing such issues.
• Inconsistent Behavior with C99: Allowing designated initializers in C would have required breaking compatibility with existing C99 implementations, which enforce a specific evaluation order. This would have introduced potential portability concerns.
• Nested Designators and Array Initializations: C99 also permits nested designators and array designated initialization, which would have added further complexity to the C language and raised concerns about inconsistent behavior.

Conclusion:

The C 11 standard committee carefully considered these technical limitations, as well as the potential for compatibility issues and inconsistent behavior, when choosing to exclude designated initializer lists. Instead, C provides a stringent evaluation order for initializer lists to ensure predictable behavior and maintain compatibility with its existing rules.

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