Difference between revisions of "Unsafe functions"
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m (Exclude seq and pseq: see Seq for details) |
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There are a number of '''unsafe functions''' in the libraries. |
There are a number of '''unsafe functions''' in the libraries. |
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* <hask>unsafePerformIO :: IO a -> a</hask> |
* <hask>unsafePerformIO :: IO a -> a</hask> |
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| + | * <hask>inlinePerformIO :: IO a -> a</hask> |
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* <hask>unsafeInterleaveIO :: IO a -> IO a</hask> |
* <hask>unsafeInterleaveIO :: IO a -> IO a</hask> |
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* <hask>unsafeInterleaveST :: ST s a -> ST s a</hask> |
* <hask>unsafeInterleaveST :: ST s a -> ST s a</hask> |
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* <hask>unsafeFreeze</hask>, <hask>unsafeThaw</hask> |
* <hask>unsafeFreeze</hask>, <hask>unsafeThaw</hask> |
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* <hask>unsafeCoerce# :: a -> b</hask> |
* <hask>unsafeCoerce# :: a -> b</hask> |
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Unsafe functions can: |
Unsafe functions can: |
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| − | * break type safety (<code>unsafeCoerce#</code>, <code>unsafePerformIO</code>), |
+ | * break type safety (<code>unsafeCoerce#</code>, <code>unsafeLocalState</code>, <code>unsafePerformIO</code>), |
| − | * break [https://okmij.org/ftp/Haskell/index.html#lazyIO-not-True equational reasoning] (<code>unsafeInterleaveIO</code>) |
+ | * or break [https://okmij.org/ftp/Haskell/index.html#lazyIO-not-True equational reasoning] (<code>unsafeInterleaveIO</code>). |
| ⚫ | |||
| − | * or weaken[https://arxiv.org/pdf/2105.03389v3 <span></span>][https://web.archive.org/web/20210506015257/https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.71.1777&rep=rep1&type=pdf <span></span>] [http://en.wikipedia.org/wiki/Parametricity parametricity] ([[Seq|<code>seq</code>]]). |
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| − | Their use (except in the case of <code>seq</code>) would require some |
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| − | 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 12:00, 24 September 2024
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.
unsafeLocalState :: IO a -> aunsafePerformIO :: IO a -> ainlinePerformIO :: IO a -> aunsafeInterleaveIO :: IO a -> IO aunsafeInterleaveST :: ST s a -> ST s aunsafeIOToST :: IO a -> ST s aunsafeIOToSTM :: IO a -> STM aunsafeFreeze,unsafeThawunsafeCoerce# :: a -> b
Unsafe functions can:
- break type safety (
unsafeCoerce#,unsafeLocalState,unsafePerformIO),
- or break equational reasoning (
unsafeInterleaveIO).
Their use 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.
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