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| author | Sebastian Graf <sebastian.graf@kit.edu> | 2018-10-14 20:32:40 +0200 |
|---|---|---|
| committer | Krzysztof Gogolewski <krz.gogolewski@gmail.com> | 2018-10-14 20:32:41 +0200 |
| commit | 448b77b93b369745e9bfbc8b46a5b87bb73dd379 (patch) | |
| tree | 8fd12e8698217f022651fe84a3ae9bf3d3e546a9 /compiler/ghci | |
| parent | 68a747c702d2432cc90d2a79a6aba0e67ac3e2c0 (diff) | |
| download | haskell-448b77b93b369745e9bfbc8b46a5b87bb73dd379.tar.gz | |
Add RubbishLit for absent bindings of UnliftedRep
Summary:
Trac #9279 reminded us that the worker wrapper transformation copes
really badly with absent unlifted boxed bindings.
As `Note [Absent errors]` in WwLib.hs points out, we can't just use
`absentError` for unlifted bindings because there is no bottom to hide
the error in.
So instead, we synthesise a new `RubbishLit` of type
`forall (a :: TYPE 'UnliftedRep). a`, which code-gen may subsitute for
any boxed value. We choose `()`, so that there is a good chance that
the program crashes instead instead of leading to corrupt data, should
absence analysis have been too optimistic (#11126).
Reviewers: simonpj, hvr, goldfire, bgamari, simonmar
Reviewed By: simonpj
Subscribers: osa1, rwbarton, carter
GHC Trac Issues: #15627, #9279, #4306, #11126
Differential Revision: https://phabricator.haskell.org/D5153
Diffstat (limited to 'compiler/ghci')
| -rw-r--r-- | compiler/ghci/ByteCodeAsm.hs | 4 | ||||
| -rw-r--r-- | compiler/ghci/ByteCodeGen.hs | 1 |
2 files changed, 5 insertions, 0 deletions
diff --git a/compiler/ghci/ByteCodeAsm.hs b/compiler/ghci/ByteCodeAsm.hs index 476a9b2efd..4473a9e9b2 100644 --- a/compiler/ghci/ByteCodeAsm.hs +++ b/compiler/ghci/ByteCodeAsm.hs @@ -460,6 +460,10 @@ assembleI dflags i = case i of LitNumWord64 -> int64 (fromIntegral i) LitNumInteger -> panic "ByteCodeAsm.literal: LitNumInteger" LitNumNatural -> panic "ByteCodeAsm.literal: LitNumNatural" + -- We can lower 'RubbishLit' to an arbitrary constant, but @NULL@ is most + -- likely to elicit a crash (rather than corrupt memory) in case absence + -- analysis messed up. + literal RubbishLit = int 0 litlabel fs = lit [BCONPtrLbl fs] addr (RemotePtr a) = words [fromIntegral a] diff --git a/compiler/ghci/ByteCodeGen.hs b/compiler/ghci/ByteCodeGen.hs index 022fe89306..9aaaa7db64 100644 --- a/compiler/ghci/ByteCodeGen.hs +++ b/compiler/ghci/ByteCodeGen.hs @@ -1539,6 +1539,7 @@ pushAtom _ _ (AnnLit lit) = do -- representation. LitNumInteger -> panic "pushAtom: LitInteger" LitNumNatural -> panic "pushAtom: LitNatural" + RubbishLit -> code N pushAtom _ _ expr = pprPanic "ByteCodeGen.pushAtom" |