[project @ 2006-01-11 11:29:49 by simonmar]

[ghc-base.git] / Data / Array / Base.hs

diff --git a/Data/Array/Base.hs b/Data/Array/Base.hs
index 5fe52d0..32f9fcd 100644 (file)
--- a/Data/Array/Base.hs
+++ b/Data/Array/Base.hs
@@ -1673,14 +1673,20 @@ thawSTUArray (UArray l u arr) = do
 
    Note that because the array is possibly not copied, any subsequent
    modifications made to the mutable version of the array may be
 
    Note that because the array is possibly not copied, any subsequent
    modifications made to the mutable version of the array may be

-   shared with the immutable version.  It is safe to use, therefore, if
-   the immutable version is never referenced again.
+   shared with the immutable version.  It is only safe to use,
+   therefore, if the immutable array is never referenced again in this
+   thread, and there is no possibility that it can be also referenced
+   in another thread.  If you use an unsafeThaw/write/unsafeFreeze
+   sequence in a multi-threaded setting, then you must ensure that
+   this sequence is atomic with respect to other threads, or a garbage
+   collector crash may result (because the write may be writing to a
+   frozen array).

 
    The non-copying implementation is supported between certain pairs
    of array types only; one constraint is that the array types must
    have identical representations.  In GHC, The following pairs of
    array types have a non-copying O(1) implementation of
 
    The non-copying implementation is supported between certain pairs
    of array types only; one constraint is that the array types must
    have identical representations.  In GHC, The following pairs of
    array types have a non-copying O(1) implementation of

-   'unsafeFreeze'.  Because the optimised versions are enabled by
+   'unsafeThaw'.  Because the optimised versions are enabled by

    specialisations, you will need to compile with optimisation (-O) to
    get them.
 
    specialisations, you will need to compile with optimisation (-O) to
    get them.