Which dialect of C is Objective-C a "strict superset" of?

I frequently hear that Objective-C is a "strict superset" of the C programming language. There are several dialects/standards of C (ie. K&R, A开发者_开发百科NSI C, C90, C99, GNU extensions...); Objective-C was first developed in the early 1980s, so it has to predate these standards. However, Objective-C 2.0 is from around 2006 or 2007, so it could be based on a more modern C dialect. So, which "C" is Objective-C a superset of?

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There's a corresponding "dialect" of Objective-C for all the standard dialects of C.

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Given that the most commonly used Objective-C compilers (GCC and Clang) are also C compilers, one would imagine that they support the C dialect(s) supported by these compilers. Apple's documentation specifically states:

The Apple compilers are based on the compilers of the GNU Compiler Collection. Objective-C syntax is a superset of GNU C/C++ syntax, and the Objective-C compiler works for C, C++ and Objective-C source code. The compiler recognizes Objective-C source files by the filename extension .m, just as it recognizes files containing only standard C syntax by filename extension .c. Similarly, the compiler recognizes C++ files that use Objective-C by the extension .mm. Other issues when using Objective-C with C++ are covered in “Using C++ With Objective-C”

So in this case Objective-C is simply regarded as an extension of either the C or C++ compiler depending on which you choose as the base language.

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What you're looking for isn't really defined. Objective C is usually thought of a strict superset of ANSI-C (which is the same as C90). However, Objective C isn't a standardized language or anything of that sort. It's description basically is "Take C, and add these features to it". It's therefore dependent on the particular compiler you're using.

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According to "Learning Objective-C" from Apple:

"Objective-C is a superset of the ANSI version of the C programming language and supports the same basic syntax as C."