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Commit 6a5c249d authored by Andrew Martin's avatar Andrew Martin Committed by Marge Bot
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[skip ci] clarify what unsound means

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docs/users_guide/ffi-chap.rst
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......@@ -111,24 +111,30 @@ very difficult to track down. (The errors likely will not manifest
until garbage collection happens.) In tabular form, these restrictions
are:
+--------------------------------+-----------------------------------------------------+
| | When value is used as argument to FFI call that is |
+--------------------------------+-------------------------+---------------------------+
| | ``foreign import safe`` | ``foreign import unsafe`` |
+--------------------------------+-----------+-------------+-----------+---------------+
| Argument Type | reads are | writes are | reads are | writes are |
+--------------------------------+-----------+-------------+-----------+---------------+
| ``Array#`` | Unsound | Unsound | Sound | Unsound |
| ``MutableArray#`` | Unsound | Unsound | Sound | Unsound |
| ``SmallArray#`` | Unsound | Unsound | Sound | Unsound |
| ``MutableSmallArray#`` | Unsound | Unsound | Sound | Unsound |
| ``ArrayArray#`` | Unsound | Unsound | Sound | Unsound |
| ``MutableArrayArray#`` | Unsound | Unsound | Sound | Unsound |
| unpinned ``ByteArray#`` | Unsound | Unsound | Sound | Unsound |
| unpinned ``MutableByteArray#`` | Unsound | Unsound | Sound | Sound |
| pinned ``ByteArray#`` | Sound | Unsound | Sound | Unsound |
| pinned ``MutableByteArray#`` | Sound | Sound | Sound | Sound |
+--------------------------------+-----------+-------------+-----------+---------------+
.. table:: Restrictions on unlifted boxed arguments passed to foreign C calls.
Cells marked as "Unsound" represent combinations that lead to
undefined runtime behavior. GHC does not reject such unsound
programs at compile time.
:widths: auto
+--------------------------------+-----------------------------------------------------+
| | When value is used as argument to FFI call that is |
+--------------------------------+-------------------------+---------------------------+
| | ``foreign import safe`` | ``foreign import unsafe`` |
+--------------------------------+-----------+-------------+-----------+---------------+
| Argument Type | reads are | writes are | reads are | writes are |
+================================+===========+=============+===========+===============+
| ``Array#`` | Unsound | Unsound | Sound | Unsound |
| ``MutableArray#`` | Unsound | Unsound | Sound | Unsound |
| ``SmallArray#`` | Unsound | Unsound | Sound | Unsound |
| ``MutableSmallArray#`` | Unsound | Unsound | Sound | Unsound |
| ``ArrayArray#`` | Unsound | Unsound | Sound | Unsound |
| ``MutableArrayArray#`` | Unsound | Unsound | Sound | Unsound |
| unpinned ``ByteArray#`` | Unsound | Unsound | Sound | Unsound |
| unpinned ``MutableByteArray#`` | Unsound | Unsound | Sound | Sound |
| pinned ``ByteArray#`` | Sound | Unsound | Sound | Unsound |
| pinned ``MutableByteArray#`` | Sound | Sound | Sound | Sound |
+--------------------------------+-----------+-------------+-----------+---------------+
When passing any of the unlifted array types as an argument to
a foreign C call, a foreign function sees a pointer that refers to the
......
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