Defines a set of useful preprocessor macros. More...

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Detailed Description

Defines a set of useful preprocessor macros.

Copyright: This code is licensed under the 3-clause BSD license. Copyright ETH Zurich, Laboratory of Physical Chemistry, Reiher Group. See LICENSE.txt for details.

Note: When applying the contained function attributes, remember that exception branch correctness must be considered during e.g. common subexpression elimination. It is helpful in many cases to additionally annotate low-level often-used functions with the noexcept specifier (if possible) to enable more optimizations.; MSVC does not implement any of these attributes, so we must replace them with empty defines if compiling with it.

Macro Definition Documentation

#define PURITY_STRONG [[gnu::const]]

Applies a strong purity function attribute

The strong purity function attribute implies all weak purity implications AND

Warning: This attribute is unchecked! Applying this attribute to functions that do not adhere to the contract leads to undefined behavior.; Be especially careful with classes. Simple getter functions that return a member by value cannot be strongly pure as they refer to state that is not encompassed by the function arguments. They may be weakly pure, however.; Be REALLY careful with this attribute on template classes' members. Make no unfounded assumptions about the template parameters behavior. If needed, constrain the template parameter with SFINAE.; Any const class member function without arguments CANNOT be of strong purity, since this is a pointer. Any access to class members within the function violates the contract.

Note: Do not expect compilers to aggressively take use of purity attributes without also providing exception guarantees. See https://kristerw.blogspot.com/2016/12/gcc-attributepure-and-c-exceptions.html

#define PURITY_WEAK [[gnu::pure]]

Applies a weak purity function attribute

The weak purity function attribute implies

return value depends only on arguments and/or global variables (class member variables are implicitly an argument, as this* is captured)
does not depend on volatile values
does not cause side effects (and does not call any impure functions)
is safe to call fewer times than the program says

Warning: This attribute is unchecked! Applying this attribute to functions that do not adhere to the contract leads to undefined behavior.

Note: Do not expect compilers to aggressively take use of purity attributes without also providing exception guarantees. See https://kristerw.blogspot.com/2016/12/gcc-attributepure-and-c-exceptions.html