Should one avoid or be careful with C99 features in C code?

Question

Some seem to say that one should avoid C99 features in C code as compilers don't really support those features. C99 is a standard from 1999, shouldn't these features be quite widespread now?

Should one avoid using C99 features in new code? In legacy code? I happen to use some C99 features quite often, should I stop doing that or be more careful with the use of those features?

I guess a better wording for this question would be: "How widely implemented is C99?" — chrisaycock, Feb 22 '11 at 19:43
@chrisaycock: I want to know wether or not to use C99 features; the wideness of implementation is just something that my question happen to depend on — Anto, Feb 22 '11 at 19:45

score 6 · Answer 1 · answered Feb 22 '11 at 20:20

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Not at all. I would highly recommend using C99 code as, with anything really, it's standardized. The compatibility between compilers is always going to vary and frustrate but it's important to embrace standardization and simply embrace what developers SHOULD, theoretically, be using. I use C99 day-in-day-out and, apart from some hoo-ha with variadic macros, everything works well, especially on VS and Xcode (obviously).

answered Feb 22 '11 at 20:20

dbramhall

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C99 works especially well on VS? Maybe if you plug-in Intel's compiler. – Nemanja Trifunovic Feb 22 '11 at 21:17
Of course... Although various systems come with this as standard. – dbramhall Feb 22 '11 at 21:56

score 4 · Accepted Answer · answered Feb 22 '11 at 19:29

Depends on how portable your code needs to be. C compilers support C99 features to a very different degree, and that can be a problem. See here for details: http://en.wikipedia.org/wiki/C99#Implementations

Personally, I would stick with C89/C90 unless I was certain I would always compile the code with the same compiler.

score 3 · Answer 3 · edited May 23 '17 at 12:40

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Despite C99's age, support remains spotty in several compilers (such as Microsoft Visual C++). Some C99 features, such as variadic macros, are supported by many compilers; other features, not so much. So you'll need to evaluate your cross-platform needs and decide if the compilers you'll need to use will support the features you want.

A second consideration is that C99 diverges more from C++. If you don't plan on ever incorporating C++, this is not an issue.

edited May 23 '17 at 12:40

Community

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answered Feb 22 '11 at 19:32

Josh Kelley

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Well, from the various comments by MS and MS developers, you can learn VS C++ isn't really meant as a C compiler (as the name implies) - it's a C++ compiler that supports some C for legacy code. If you develop new code in C, VS C++ is simply not the right compiler to use (however, you can use the IDE and plug in a different compiler, with some limitations). – sleske Aug 25 '14 at 12:01

Should one avoid or be careful with C99 features in C code?

3 Answers3