Gregory Wright wrote:
I have ghc-6.6 (darcs version from 20070405) running registerized on
FreeBSD/amd64. The FreeBSD version is 6.2.
The problem with the compiler crash turned out to be simple. In the
FreeBSD header file regex.h, regex_t is defined as
typedef struct {
int re_magic;
size_t re_nsub; /* number of parenthesized
subexpressions */
__const char *re_endp; /* end pointer for REG_PEND */
struct re_guts *re_g; /* none of your business :-) */
} regex_t;
The problem is that the "re_magic" field is defined as an int. When
building
the .hc files on the i386 host, the re_nsub field is at an offset of 4.
On the
amd64 target, it is at an offset of 8. In the ghc binding to the regex
functions,
re_nsub is used to compute how much memory to allocate in a call to
allocaBytes. This leads to garbage being passed to newPinnedByteArray#.
The fix is to patch libraries/base/Text/Regex/Posix.hs on the amd64 target:
--- libraries/base/Text/Regex/Posix.hs.sav Thu Apr 5 12:05:22 2007
+++ libraries/base/Text/Regex/Posix.hs Thu Apr 5 12:05:45 2007
@@ -106,7 +106,7 @@
regexec (Regex regex_fptr) str = do
withCString str $ \cstr -> do
withForeignPtr regex_fptr $ \regex_ptr -> do
- nsub <- ((\hsc_ptr -> peekByteOff hsc_ptr 4)) regex_ptr
+ nsub <- ((\hsc_ptr -> peekByteOff hsc_ptr 8)) regex_ptr
{-# LINE 109 "Posix.hsc" #-}
let nsub_int = fromIntegral (nsub :: CSize)
allocaBytes ((1 + nsub_int) * (16)) $ \p_match -> do
With this patch, we are pretty close.
Aha. Text/Regex/Posix.hs is generated from Text/Regex/Posix.hsc by hsc2hs, but
this is done on the *host* rather than the *target* when bootstrapping, and thus
generates the wrong results. If you'd run hsc2hs on the target, then
Text/Regex/Posix.hs would have been correct, but you can't do this because
hsc2hs is a Haskell program. You could take the .c file generated by hsc2hs on
the host and compile/run it on the target, but that's a hassle, so instead our
policy is that we don't rely on any hsc2hs-generated code for bootstrapping.
Unfortunately I broke the rules by accident when I introduced the dependency on
regex. I can't think of an easy way to enforce the rule, at least at the
moment, since there are other hsc2hs-processed modules that we happen to not
depend on in GHC (System.Time and System.CPUTime).
This will be fixed as a side effect of
http://hackage.haskell.org/trac/ghc/ticket/1160. Also after the base reorg we
might find we have no hsc2hs-generated code left in base and we can disable
hsc2hs to prevent this happening again.
Cheers,
Simon
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