How Complete Are C99 and C11 Implementations on GCC?

Introduction

The GNU Compiler Collection (GCC) is one of the most widely used compilers for the C programming language. As of the last update in August 2023, GCC has made considerable progress in implementing the C99 and C11 standards.

C99 Implementation

Completeness: GCC's support for C99 is considered robust. Most of the features specified in the C99 standard are implemented, including syntax for variable-length arrays, inline functions, new data types such as long long int, complex numbers, designated initializers, and new preprocessor directives.

However, there may still be some edge cases or less commonly used features that may not be fully supported or may have specific limitations. Detailed information can be found on the Status of C99 features in GCC page.

C11 Implementation

Completeness: GCC's support for C11 is also quite comprehensive, though it may not be as complete as C99. Key features supported include static assertions, thread support via threads.h, atomic operations via stdatomic.h, and improved type generic programming via _Generic. Anonymous structures and unions are also supported.

While GCC's implementation of C11 is solid, some features, particularly those related to multi-threading and atomics, might have varying levels of support depending on the platform and the version of GCC being used. For detailed information, refer to the C11Status - GCC Wiki.

Conclusion

Overall, GCC provides a reliable environment for developing C programs using both C99 and C11 standards. To ensure the most accurate and detailed information, it is always a good idea to check the official GCC documentation or the release notes for the specific version you are using, as updates and improvements are continuously made.

Additional Resources

The GCC project maintains a table of the Status of C11 in gcc and the equivalent for LLVM/Clang is found at C1z C14 C11 and C98 Status.

For comprehensive details on the C99 and C11 standards, you can refer to the Status of C99 features in GCC and the C11Status - GCC Wiki.