Compiled Library versus Source Code

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One big difference between Go and many other languages is the notion of source availability. Traditionally programming languages have depended on using a pre-compiled library — both to avoid recompiling the library and to protect source as intellectual property. Go was born in an era of faster computing and prolific open source; it relies on having access to all source at compile time, including library code. Go takes advantage of this to make interesting optimizations, especially around when a structure escapes the stack to the heap. Keeping structures off the heap means they do not need to be tracked for garbage collection, and the Go compiler manages this automatically. The interesting consequence is that, for a given use of a library as source, an application structure may or may not escape to the heap depending on how it flows through the code — an optimization only possible when all source is compiled together.

go2cs converts each package separately, so it chooses every function’s signature from that package alone. An exported function’s pointer parameter is a heap box (ж<T>), because another package may call it. An unexported function, whose callers are all visible, can take a C# ref instead, and a local whose address reaches only such parameters stays a plain local (see Pointers). A future option could distinguish optimizations targeted at a compiled library (very safe escape analysis) versus a standalone application (more aggressive). Already-converted packages are referenced as compiled libraries — the consumption model most C# developers are accustomed to — which takes two pieces, both in place: -recurse=nuget maps each imported Go package to its published go.<pkg> package reference, and the exported metadata a consumer would otherwise scrape out of the dependency’s converted source travels with the converter (see A NuGet-referenced standard library carries its exported metadata IN THE CONVERTER).

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