haskell - ghc - 重复的编译...消息集

Question

在构建包时，我注意到重复的“正在编译...”消息集，例如：

Preprocessing library syb-0.3.7...
[ 1 of 16] Compiling Data.Generics.Basics ( ... )
[ 2 of 16] Compiling Generics.SYB.Basics ( ... )
[ 3 of 16] Compiling Data.Generics.Instances ( ... )
...
[16 of 16] Compiling Generics.SYB     ( ... )
[ 1 of 16] Compiling Data.Generics.Basics ( ... )
[ 2 of 16] Compiling Generics.SYB.Basics ( ... )
[ 3 of 16] Compiling Data.Generics.Instances ( ... )
...
[16 of 16] Compiling Generics.SYB     ( ... )
In-place registering syb-0.3.7...
Running Haddock for syb-0.3.7...
Preprocessing library syb-0.3.7...

我在 cabal 沙箱中构建时注意到了这一点。

我只是好奇发生了什么事。真的是两次编译源码吗？这会一直发生吗？它与在沙箱中构建有关吗？

Answer 1

It is really compiling the source twice. It is not related to building in a sandbox. It does not always have to happen -- you can ask cabal not to do this in its config file by toggling the library-profiling flag. However, it's strongly recommended that you do not do this: at the moment, cabal does not have good support for taking a dependency tree with no profiling libraries and rebuilding them all with profiling.