add module intro from Haskell 2010

diff --git a/Foreign/Marshal/Alloc.hs b/Foreign/Marshal/Alloc.hs
index c0dfb43..4b35c27 100644 (file)
--- a/Foreign/Marshal/Alloc.hs
+++ b/Foreign/Marshal/Alloc.hs
@@ -9,7 +9,29 @@
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- Marshalling support: basic routines for memory allocation
+-- The module "Foreign.Marshal.Alloc" provides operations to allocate and
+-- deallocate blocks of raw memory (i.e., unstructured chunks of memory
+-- outside of the area maintained by the Haskell storage manager).  These
+-- memory blocks are commonly used to pass compound data structures to
+-- foreign functions or to provide space in which compound result values
+-- are obtained from foreign functions.
+-- 
+-- If any of the allocation functions fails, a value of 'nullPtr' is
+-- produced.  If 'free' or 'reallocBytes' is applied to a memory area
+-- that has been allocated with 'alloca' or 'allocaBytes', the
+-- behaviour is undefined.  Any further access to memory areas allocated with
+-- 'alloca' or 'allocaBytes', after the computation that was passed to
+-- the allocation function has terminated, leads to undefined behaviour.  Any
+-- further access to the memory area referenced by a pointer passed to
+-- 'realloc', 'reallocBytes', or 'free' entails undefined
+-- behaviour.
+-- 
+-- All storage allocated by functions that allocate based on a /size in bytes/
+-- must be sufficiently aligned for any of the basic foreign types
+-- that fits into the newly allocated storage. All storage allocated by
+-- functions that allocate based on a specific type must be sufficiently
+-- aligned for that type. Array allocation routines need to obey the same
+-- alignment constraints for each array element.
 --
 -----------------------------------------------------------------------------