[ ghc-Bugs-1106211 ] GHC panic

Bugs item #1106211, was opened at 2005-01-20 19:39
Message generated for change (Settings changed) made by simonmar
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=108032&aid=1106211&group_id=8032

Category: Compiler
Group: 6.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
>Assigned to: Simon Marlow (simonmar)
Summary: GHC panic

Initial Comment:
This concerns GHC HEAD (6.3) on 20 Jan 2005.

I'm afraid this is not going to be a very useful bug
report,
but I thought I'd file my observations anyway.

When compiling a file AFRPTestsReact.hs, GHC panics:

seshat-257% ghc -c -fglasgow-exts -package lang
-package concurrent -i../src AFRPTestsReact.hs
ghc-6.3: panic! (the `impossible' happened, GHC version
6.3):
        Ix{Int}.index: Index (257) out of range ((0,118))
 
Please report it as a compiler bug to
glasgow-haskell-bugs@xxxxxxxxxxx,
or http://sourceforge.net/projects/ghc/.

I start to work on creating a small test case that will
exhibit
the bug by making a copy of the file under a different
name.

But when I compile that file, with the exact same
command line arguments, just to routinely ensure that I
can recreate the bug before I start modifying things,
everything works fine!

I compile the old file again, and again GHC panics, despite
the files being identical , living in the same
directory, being
compiled with the same command line arguments and
from the very same prompt (same environment variables).

I try a few times, and GHC consistently behaves as
described: old file => panic, any copy of the file =>
compiles fine.

Eventually, I "touch" the old file. And then it
compiles just fine!

Possibly some problem with reading file attributes???

Sorry that I cannot provide more info (e.g.
the exact time and date of the file): I'm no
longer able to recreate the problem.

/Henrik

e-mail: nhn@xxxxxxxxxxxxx


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Comment By: Simon Marlow (simonmar)
Date: 2005-01-21 13:00

Message:
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It sounds like you have an old .hi file lying around
generated by a previous (development, unreleased) version of
GHC.  GHC only detects version mismatches with .hi files at
the granularity of release versions (6.2, 6,4 etc.), it
won't detect that a .hi file was created by version
6.3.20050110 and we're at 6.3.20050111, for example. 
Nevertheless, such version mismatches can cause compiler
crashes like the one you describe.

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