Re: [Valgrind-users] HowTo track write-access to *valid* addresses

[Nicholas N. <nj...@cs...>]

On Wed, 22 Feb 2006, Joe Mason wrote:

>>>  Is there a way to (ab)use valgrind 3.1 to track all write-access
>>>  to a specific address?
>>
>> At least on x86 and amd64 you don't need VG for that.
>> Gdb hardware watchpoints get you there much faster.
>
> However, if you can't use gcc, add this to your source:
>
>  #include <valgrind/memcheck.h>
>
>  ...
>  // make valgrind report all reads and writes to an address
>  VALGRIND_MAKE_NOACCESS(addr, numbytes);
>  // make valgrind stop reporting reads to the address
>  VALGRIND_MAKE_READABLE(addr, numbytes);
>
> (By default if you allocate some memory, valgrind marks it both READABLE
> and WRITABLE, so I *think* you have to turn those off with NOACCESS.
> But I can't recall - MAKE_READABLE might automatically turn off WRITABLE
> The MAKE_NOACCESS line may not be necessary - MAKE_READABLE might
> automatically turn off WRITABLE as well.)

MAKE_NOACCESS is the right thing to use.  Our use of the term "readable" is 
a bit confusing, because it really means "readable and writable".

Nick