#2169: Compilation fails first time without giving an error, later succeeds
without changing code
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Reporter: nccb | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.8.3
Component: Compiler | Version: 6.8.2
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Architecture: x86_64 (amd64)
Os: Linux |
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Comment (by nccb):
I'm having real trouble slimming down the testcase. If I remove modules
from the build process, the error goes away. If I remove some functions,
it also disappears. Here is what I am fairly certain of:
* Options in an OPTIONS_GHC pragma in data/OrdAST.hs are being applied to
flow/FlowGraph.hs, as long as it is the next module in the build process
for --make.
* The error occurs even though flow/FlowGraph.hs doesn't even import
data/OrdAST.hs
* The error always occurs if you add a function (and thus change the
automatically-determined export list) in a module they both depend on,
such as common/Utils.hs and recompile
* The error can occur even when data/OrdAST.hs is not recompiled
(presumably it is still scanned for the module dependencies)
* The error seems to disappear when data/OrdAST.hs exports a function; the
error only occurs when data/OrdAST.hs exports nothing at all, or exports
only type-class instances (for types not in its view).
* Removing module imports from Main that are normally compiled before
data/OrdAST.hs and flow/FlowGraph.hs, and that are directly impored by
neither, can make the error go away.
* The error seems to only occur if both modules import *qualified* AST,
but as different things (e.g. import qualified AST, versus import
qualified AST as A). I think every other module in the code imports AST
as A, so that may be a bit of a confounding factor too.
* If I move all the modules from their subdirectories into the main
directory, the problem disappears
I had suspected the problem was to do with the orphan instance
declarations in data/OrdAST.hs but the error seems to occur even with the
instance declarations removed. My best guess now is that the problem is
somehow to do with the qualified imports, not exporting anything, the
OPTIONS_GHC pragma and seems to be very specific to the build order.
I've attached the tarball. Extract the files and run "sh compile.sh". If
that doesn't produce the error immediately, let the compilation finish and
then in common/Utils.hs, uncomment/comment (it's the toggling that does
it) the two "foo" lines near the top of the file. Then re-run
compile.sh. On my machine this will then produce the problem every time.
If you re-run compile.sh until compilation succeeds, you can then toggle
the lines in common/Utils.hs again to produce the problem again.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2169#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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