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Asked: 2026-05-25T00:07:05+00:00

I’m writing a few classes and structs that could benefit from 16-byte alignment. Instead

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I’m writing a few classes and structs that could benefit from 16-byte alignment. Instead of using compiler-specific hacks, I’d rather use the new C++0x alignas functionality for future portability. However, using it outside of appropriate #ifdef or #ifndef guards will obviously cause errors on compilers without alignas support.

I did a quick search for similar questions, and the closest match had an answer recommending Boost.Config. Unfortunately, Boost.Config doesn’t seem to include any functionality for querying alignas support. Are there any other #ifdefs or #ifndefs I can use to figure out whether the compiler supports it?

Thanks!

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  1. Editorial Team

    There are no direct feature-support macros for the various C++0x (C++11) facilities. There only two ways I can think of to determine their presence.

    1. Keep a list of which compilers support them, and use #ifdef directives based on the compiler-supplied version macros such as __GNUC__ and _MSC_VER, or
    2. Use a feature-detection script such as autoconf to detect compiler support prior to building, and construct a header file with your own macros indicating support for the feature, or lack thereof.

    Using Boost.Config is actually an example of both: Boost has a set of feature-detection scripts which are run during Boost development, and then the results hard-coded in the Boost.Config headers based on the compiler version macros.

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