error function is not lazy
C:\Neil\Temp>type Test.hs
main = error $ cycle "Hello\n"
C:\Neil\Temp>ghc --make Test.hs
[1 of 1] Compiling Main ( Test.hs, Test.o )
Linking Test.exe ...
C:\Neil\Temp>test
-- hangs forever
The error message seems to get buffered, which means long/infinite messages are never displayed. GHCi does evaluate error lazily. The error function is particularly useful for debugging, which is where I encountered this problem.
It appears trace has a similar issue of buffering in GHC compiled programs, but I am not certain.
Trac metadata
Trac field | Value |
---|---|
Version | 6.8.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture | Unknown |