Introduce a new type, PtrdiffT.  Replace lots of uses of OffT (all those
that are memory offsets) with PtrdiffT;  OffT should only be used for file
sizes and offsets.

Change Off64T from a ULong to a Long, as it should be.  Replace some uses
of ULong in the address space manager with Off64T to match.

Also add a comment explaining the meanings of the basic types like Addr,
OffT, SizeT, etc.

Also fix the prototype for VG_(pread) -- the last arg is an OffT, not an
Int.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@8959 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/drd/drd_error.h b/drd/drd_error.h
index 6b56051..b72b82e 100644
--- a/drd/drd_error.h
+++ b/drd/drd_error.h
@@ -81,7 +81,7 @@
 struct {                      // Used by:
    AddrKind    akind;         //   ALL
    SizeT       size;          //   ALL
-   OffT        rwoffset;      //   ALL
+   PtrdiffT    rwoffset;      //   ALL
    ExeContext* lastchange;    //   Mallocd
    DrdThreadId stack_tid;     //   Stack
    DebugInfo*  debuginfo;     //   Segment