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by Joker_vD 706 days ago
> A JSON decoder right in the compiler could easily be faster than generation involving extra tool invocations and multiple passes.

It also can easily be slower: C++ templates are not exactly known for their blazingly fast compilation speed. Besides, the program they encode in this case is effectively being interpreted by the C++ compiler which, I suppose, is not really optimized for that: it's still mostly oriented around emitting optimized machine code.
1 comments
kazinator 705 days ago
> C++ templates are not exactly known for their blazingly fast compilation speed.

Compared to what alternative that does the same thing, in C++?

Modern C++ compilers, as such, are slow as molasses, on multi-GHz hardware with huge L1 and L2 caches, whether your code uses templates or not.

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Joker_vD 705 days ago
The alternative would be to run the JSON through e.g. jq/sed and make it dump out a chunk of C++ that would create an object with proper fields and subobjects. This C++ code will have about zero template chicanery; instead, it would just call constexpr constructors which, I imagine, would be entirely boring — this C++ code will be compiled much faster.
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