Re: [Valgrind-users] Using memcheck to treat memory as read-only

[Philippe W. <phi...@sk...>]

On Wed, 2013-08-07 at 08:13 -0700, John Reiser wrote:
> > Is there any support in memcheck for a client request to treat a block of memory as read-only?  I know memory can be defined as accessible/not accessible or defined/undefined, but I don’t see anything for “writable”.  It would be really nice to be able to add client requests so that after a block of
> > memory is initialized, to be able to tell memcheck that certain bytes should never be written again, because they have been initialized (e.g. pointer to another object).
> 
> No; "read only" is not one of the states in the current memory accounting info.
Effectively.
memcheck/mc_main.c gives some background info:
   Aside: the V+A bits are less precise than they could be -- we have no way
   of marking memory as read-only.  It would be great if we could add an
   extra state VA_BITSn_READONLY.  But then we'd have 5 different states,
   which requires 2.3 bits to hold, and there's no way to do that elegantly
   -- we'd have to double up to 4 bits of metadata per byte, which doesn't
   seem worth it.