Oleg,
I am using GHC 6.12.3
Here a reproduction:
in the file Template.hs
proc () = runIO $ do runQ [|1+1|]
proc' () = [|1+1|]
In the file Main.hs
i1 = $(proc ()) -- fails at compile time with "Segmentation
fault/access violation in generated code". Maybe is it the expected
behavior, I do not know.
i2 = $(proc' ()) -- sucessfull
i3 = proc() -- sucessful but proc is executed at "runtime"
main = ...
Hope it is clear enough otherwise let me know.
Regards
J-C
On Mon, Nov 29, 2010 at 4:45 AM,
Hello!
But, please, correct me if I am wrong, in your example, the splicer are executed at run time and not at compile time.
With TH, it becomes a bit difficult to tell what is exactly `compile time'. One can say however that when the code is ready to be spliced in at the top level, the IO actions in its splices must have been completed.
I have modified your example to make it run at compile time and I get a (compile time) segmentation fault.
As I mentioned, the code was specifically designed to cause something like segmentation fault. Sneaking out free variables is definitely the bad thing. The principle of exchanging data between splices (using runQ/runIO) is valid and could be used for good things, too.
I am wondering though what GHC version and command-line parameters are you using? On my system. with GHC 6.10.3, I tried running the original and modified code in GHCi and GHC (with and without -O2) and did not get segmentation fault. Could you provide more details about your system so to reproduce the segfault? I think Simon Peyton-Jones would really like to know all that.
Cheers, Oleg