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| author | nineonine <mail4chemik@gmail.com> | 2022-11-10 21:03:11 -0800 |
|---|---|---|
| committer | Matthew Pickering <matthewtpickering@gmail.com> | 2023-01-27 16:12:13 +0000 |
| commit | 1d6f42895641555e18a2e4cdc664759b6d00dac4 (patch) | |
| tree | ab93abbc0ceb37714a3bbaebfe206f36a3b951a8 /docs/users_guide | |
| parent | b95dab8b0807533de258e5fe985822ae393f5fef (diff) | |
| download | haskell-wip/T22043.tar.gz | |
CApiFFI: add ConstPtr for encoding const-qualified pointer return typeswip/T22043
Previously, when using `capi` calling convention in foreign declarations,
code generator failed to handle const-cualified pointer return types.
This resulted in CC toolchain throwing `-Wincompatible-pointer-types-discards-qualifiers`
warning.
`Foreign.C.Types.ConstPtr` newtype was introduced to handle these cases -
special treatment was put in place to generate appropritetly qualified C
wrapper that no longer triggers the above mentioned warning.
Fixes #22043.
Diffstat (limited to 'docs/users_guide')
| -rw-r--r-- | docs/users_guide/9.6.1-notes.rst | 3 | ||||
| -rw-r--r-- | docs/users_guide/exts/ffi.rst | 12 |
2 files changed, 15 insertions, 0 deletions
diff --git a/docs/users_guide/9.6.1-notes.rst b/docs/users_guide/9.6.1-notes.rst index e78972a919..f0961348f3 100644 --- a/docs/users_guide/9.6.1-notes.rst +++ b/docs/users_guide/9.6.1-notes.rst @@ -167,6 +167,9 @@ Runtime system ``ghc`` library ~~~~~~~~~~~~~~~ +- Add `Foreign.C.Types.ConstPtr` was added to encode ``const``-qualified pointer return + types in foreign declarations when using ``CApiFFI`` extension. + ``ghc-heap`` library ~~~~~~~~~~~~~~~~~~~~ diff --git a/docs/users_guide/exts/ffi.rst b/docs/users_guide/exts/ffi.rst index b490ac662d..37d96a0a68 100644 --- a/docs/users_guide/exts/ffi.rst +++ b/docs/users_guide/exts/ffi.rst @@ -437,6 +437,18 @@ specified. The syntax looks like: :: data {-# CTYPE "unistd.h" "useconds_t" #-} T = ... newtype {-# CTYPE "useconds_t" #-} T = ... +In case foreign declarations contain ``const``-qualified pointer return +type, ``ConstPtr`` from :base-ref:`Foreign.C.ConstPtr` may be used to +encode this, e.g. :: + + foreign import capi "header.h f" f :: CInt -> ConstPtr CInt + +which corresponds to + +.. code-block:: c + + const *int f(int); + ``hs_thread_done()`` ~~~~~~~~~~~~~~~~~~~~ |