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| author | Alec Theriault <alec.theriault@gmail.com> | 2019-01-10 23:44:04 -0800 |
|---|---|---|
| committer | Ben Gamari <ben@well-typed.com> | 2019-01-23 14:07:28 -0500 |
| commit | 5341edf3635f2875271acc469570481c52000374 (patch) | |
| tree | 98fad051d47888913fa8492170ff537330e5c7eb /compiler | |
| parent | a90a2aea94b306cf557e74c4c3ed65959d05c20c (diff) | |
| download | haskell-5341edf3635f2875271acc469570481c52000374.tar.gz | |
Error out of invalid Int/Word bit shifts
Although the Haddock's for `shiftL` and `shiftR` do require the number
of bits to be non-negative, we should still check this before calling
out to primitives (which also have undefined behaviour for negative bit
shifts).
If a user _really_ wants to bypass checks that the number of bits is
sensible, they already have the aptly-named `unsafeShiftL`/`unsafeShiftR`
at their disposal.
See #16111.
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/prelude/PrelRules.hs | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/compiler/prelude/PrelRules.hs b/compiler/prelude/PrelRules.hs index f8b8f91bcc..7111c7b07a 100644 --- a/compiler/prelude/PrelRules.hs +++ b/compiler/prelude/PrelRules.hs @@ -474,12 +474,11 @@ shiftRule shift_op ; case e1 of _ | shift_len == 0 -> return e1 - | shift_len < 0 || wordSizeInBits dflags < shift_len - -> return (mkRuntimeErrorApp rUNTIME_ERROR_ID wordPrimTy - ("Bad shift length" ++ show shift_len)) -- Do the shift at type Integer, but shift length is Int Lit (LitNumber nt x t) + | 0 < shift_len + , shift_len <= wordSizeInBits dflags -> let op = shift_op dflags y = x `op` fromInteger shift_len in liftMaybe $ Just (Lit (mkLitNumberWrap dflags nt y t)) |