CODEWITHSUNDEEP
cterminalclang
joek
joek

Reputation: 21

Changing clang to compile in C11 or higher?

I'm following a tutorial on learning C. I'm currently using a Mac with clang 11.0.3. It is in C99 by default (I'm getting the error: warning: implicit declaration of function 'of' is invalid in C99 [-Wimplicit-function-declaration].) I'm using xcode 11.5.

How do I update/change the default of clang to C11 or higher?

Upvotes: 2

Views: 3786

Answers (1)

Gilles 'SO- stop being evil'
Gilles 'SO- stop being evil'

Reputation: 107739

You can look up the documentation with man clang on your system or online on the Clang website (https://clang.org → “Getting started” → “User's Manual” link on the left).

clang supports the -std option, which changes what language mode clang uses. The supported modes for C are c89, gnu89, c99, gnu99, c11, gnu11, c17, gnu17, c2x, gnu2x, and various aliases for those modes. If no -std option is specified, clang defaults to gnu17 mode.

Note that since you're seeing C99 as the language version, your IDE is likely passing a -std option already. I don't know where to control compiler options in Xcode but Setting C compile flags in xcode might help.

The Clang documentation is not always complete or clear. Many features of Clang mimic GCC, and GCC often has better documentation. The section on C dialect options in the GCC manual has more information about -std and its values. You need to be careful because Clang doesn't always work exactly like GCC, but the GCC documentation is often helpful as long as you remember that it may not always apply to Clang.

None of this will help you anyway because switching from C99 to C11 wouldn't fix this particular error. Implicit function declarations are a deprecated feature in C89 which was made invalid in C99, and of is not a new keyword in C11, so either your code is bad-style C89 or more likely there's a typo and of should not be a function name.

Upvotes: 3

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