logoalt Hacker News

meghprkh • today at 4:46 PM • 1 reply • view on HN

Why would they not do something like?

  + #if !(defined __GLIBC_COMPILER_SUPPORTS_ATTRIBUTES__)
  - #if !(defined __GNUC__ || defined __clang__ || defined __TINYC__)
  # define __attribute__(xyz)     /* Ignore */
  #endif
(or probably a more fine grained for each attribute they try to use)

Considering such checks are fairly conventional in downstream C++ libraries based on compilers (for example checking OS platform or compiler, e.g. [Boost.Config](https://www.boost.org/doc/libs/latest/libs/config/). Modern C++ even went ahead and standardized this somewhat https://en.cppreference.com/cpp/utility/feature_test )

Replies

ventana • today at 5:56 PM

I have no knowledge of this specific "why", but my general experience shows that feature flags, while almost universally better than checks for the specific software version in hope that it has proper support for a feature, appear only as a replacement to platform / software detection, after a few years of struggle.

It's probably just natural for software developers (myself included), whenever only FooZoid v5 supports frobnicate(), say "#ifdef FOOZOID_V5" and go back to your business, rather than introducing "FROBNICATE_SUPPORTED".

Also, when you try to ask for a feature flag in the code review, people will throw YAGNI at you, and they might be not wrong, at least for the first few years. After that, it's a costly refactor.