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Diffstat (limited to 'hadrian/src/Rules/Libffi.hs')
| -rw-r--r-- | hadrian/src/Rules/Libffi.hs | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/hadrian/src/Rules/Libffi.hs b/hadrian/src/Rules/Libffi.hs index 86238c30a4..d629110c40 100644 --- a/hadrian/src/Rules/Libffi.hs +++ b/hadrian/src/Rules/Libffi.hs @@ -13,8 +13,25 @@ import Settings.Builders.Common import Target import Utilities -{- Note [Libffi indicating inputs] +{- +Note [Uses of libffi in GHC] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +GHC uses libffi for two things: + * it is always used to perform foreign calls in interpreted code. This is + implemented in "GHCi.FFI" in the `ghci` library). N.B. it is *not* used for + foreign calls in compiled code, which are rather handled by the code generator. + + * it is used by some platforms for "adjustors" used to setup calls into + Haskell from `foreign export`s. This is implemented in `rts/Adjustor.c`; see + Note [Adjustors] in that file. + + Note that on some platforms (e.g. x86-64) we use our own home-grown + adjustors logic instead of libffi. Consequently, the RTS's dependency on + libffi is conditional on 'Oracles.Settings.useLibFFIForAdjustors'. + +Note [Libffi indicating inputs] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ First see https://gitlab.haskell.org/ghc/ghc/wikis/Developing-Hadrian for an explanation of "indicating input". Part of the definition is copied here for your convenience: |