Compiler extension for evaluating a "complex" function (with known input values) at compile time, regardless of `constexpr`

Question

Please see this example . An attempt to use constexprto obtain an estimate of compilation time would be extremely difficult, if not impossible.

However, when a function is called, all arguments are known at compile time. Theoretically (if there is some optimization attribute?), The Compiler can pause parsing, create a small program using a function, compile it, run it and get the result to create a char constant that will be used mainly to compile the program.

I understand that one of the problems can be, for example, cross-compilation: you can run the program only from the compiler, if the compiler can create a program that can run on a machine that builds. But this does not seem impossible to overcome.

There is no doubt: I am not the first to think about it. But I tried to search, and I could find things constexprand template. Is there any plan for implementing such a function in any compiler in the future? This function can also be rephrased as: Give the opportunity to write a C ++ program in your C ++ source, which the compiler can compile and run on demand to create a constant.

Answer 1

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https://isocpp.org/wiki/faq/cpp14-language#extended-constexpr

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Answer 2

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