Difference between revisions of "Unsafe functions"
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| − | I think <code>unsafePerformIO</code> might actually be a pretty good alternative, we just need to understand how to use it safely [...] |
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| + | A colleague [...] asked me today whether I know how to use <code>unsafePerformIO</code> safely. And I realized I have no idea. |
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Unsafe functions can break type safety (unsafeCoerce#, unsafePerformIO), |
Unsafe functions can break type safety (unsafeCoerce#, unsafePerformIO), |
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| − | interfere with lazy IO (unsafeInterleaveIO), or break [http://en.wikipedia.org/wiki/Parametricity parametricity] (seq). |
+ | interfere with lazy IO (unsafeInterleaveIO), or break [http://en.wikipedia.org/wiki/Parametricity parametricity] (<code>seq</code>). |
| − | Their use (except in the case of < |
+ | Their use (except in the case of <code>seq</code>) would require some |
kind of assurance on the part of the programmer that what they're doing |
kind of assurance on the part of the programmer that what they're doing |
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is safe. |
is safe. |
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<code>unsafe</code> is also a keyword which can be used in a [http://haskell.org/haskellwiki/Performance/FFI foreign import declaration]. |
<code>unsafe</code> is also a keyword which can be used in a [http://haskell.org/haskellwiki/Performance/FFI foreign import declaration]. |
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Revision as of 05:44, 11 August 2022
A colleague [...] asked me today whether I know how to use unsafePerformIO safely. And I realized I have no idea.
There are a number of unsafe functions in the libraries.
unsafePerformIO :: IO a -> aunsafeInterleaveIO :: IO a -> IO aunsafeInterleaveST :: ST s a -> ST s aunsafeIOToST :: IO a -> ST s aunsafeIOToSTM :: IO a -> STM aunsafeFreeze, unsafeThawunsafeCoerce# :: a -> bseq :: a -> b -> b
Unsafe functions can break type safety (unsafeCoerce#, unsafePerformIO),
interfere with lazy IO (unsafeInterleaveIO), or break parametricity (seq).
Their use (except in the case of seq) would require some
kind of assurance on the part of the programmer that what they're doing
is safe.
unsafe is also a keyword which can be used in a foreign import declaration.
This article is a stub. You can help by expanding it.