Is there a portable equivalent of gcc's __attribute__ (pure)?

I'm writing some code where there are a bunch of simple pure functions that get called a lot. It's perfectly safe if these functions get get optimized to be called less often.

Currentl开发者_如何学编程y I am using gcc as my compiler and I'm wondering if there is a portable way of doing:

int foo(int) __attribute__ ((pure))

Info about the pure keyword can be found here: http://www.ohse.de/uwe/articles/gcc-attributes.html#func-pure

How would I go about implementing something like this if the pure keyword is not available?

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Since C++11, you can use the standardized attribute syntax with GCC specific attributes:

[[gnu::pure]]
int foo(int)

Since C++17, this is guaranteed to be fine on any compiler, since if they don't recognize [[gnu::pure]], they must ignore it without error.

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No, there is not.

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#ifdef __GNUC__
#define __pure __attribute__((pure))
#else
#define __pure
#endif

Use __pure when you need it

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I think the portable way is to inline the functions and hope the compiler will figure out the rest.