Why do compilations take so long?
I am designing a programming language and one of the problems i was thinking was why do programming languages take long to compile. Assumed c++ takes a long time because it needs to parse and compile a header everytime it compiles a file. But i -heard- precompiled headers take as long? i suspect c++ is not the only language that has this problem.
一个C ++特有的问题使其变得非常慢，因为与几乎任何其他语言不同，您无法独立于语义分析来解析它。
Compiling is a complicated process which involves quite a few steps:
(Leaving aside linking.)
Naturally, this will take some time for longer programs.
Precompiled headers are way faster, as has been known at least since 1988.
The usual reason for a C compiler or C++ compiler to take a long time is that it has to #include, preprocess, and then lex gazillions of tokens.
As an exercise you might find out how long it takes just to run cpp over a typical collection of header files---then measure how long it takes to lex the output.
gcc -O uses a very effective but somewhat slow optimization technique developed by Chris Fraser and Jack Davidson. Most other optimizers can be slow because they involve repeated iteration over fairly large data structures.
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