#2249: Undeclared variable in cmm reports as panic
-------------------------------+--------------------------------------------
Reporter: millenix | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.9 | Severity: minor
Keywords: | Testcase:
Architecture: x86_64 (amd64) | Os: Linux
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In CMM code, if one makes an assignment to a variable that's not been
declared, the compiler panics, in addition to reporting an almost sensible
error message.
Here's code to make it happen:
{{{
testingbug
{
var = 1;
}
}}}
And here's the output it causes:
{{{
ghc-6.9.20080305: panic! (the 'impossible' happened)
(GHC version 6.9.20080305 for x86_64-unknown-linux):
CmmParse: var not a register
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
I see two problems here:
1. As the output notes, the compiler should not panic just because the
user fed it noticeably bad code. It should just report the underlying
message, with a line/column reference to the offending code.
2. The error message should quote the variable name about which it's
complaining. When I initially discovered this, the variable name in
question was `data`, and that was rather confusing.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2249>
GHC <http://www.haskell.org/ghc/>
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