Re: Quiet valgrind warnings in init_current_teb

[Mike Hearn]

Hmm, are you sure this isn't a bug in Valgrind itself? The code it's
warning on is this:

inline static void wine_ldt_set_limit( LDT_ENTRY *ent, unsigned int limit )
{
    if ((ent->HighWord.Bits.Granularity = (limit >= 0x100000))) limit >>= 12;
    ent->LimitLow = (WORD)limit;
    ent->HighWord.Bits.LimitHi = (limit >> 16);
}

but unless I'm reading it wrong this is not testing ent
before initialization at all, it's testing limit, assigning to ent, then
testing the result of that assignment ... which seems to be valid.

Of course, working around bugs in Valgrind may be a useful thing to do for
now ... that code is seriously terrifying stuff. And I thought Wine was
scary :)

thanks -mike

Quiet valgrind warnings in init_current_teb

[Eric Pouech]

Mike Hearn wrote:
> Hmm, are you sure this isn't a bug in Valgrind itself? The code it's
> warning on is this:
>
> inline static void wine_ldt_set_limit( LDT_ENTRY *ent, unsigned int limit )
> {
>     if ((ent->HighWord.Bits.Granularity = (limit >= 0x100000))) limit >>= 12;
>     ent->LimitLow = (WORD)limit;
>     ent->HighWord.Bits.LimitHi = (limit >> 16);
> }
>
> but unless I'm reading it wrong this is not testing ent
> before initialization at all, it's testing limit, assigning to ent, then
> testing the result of that assignment ... which seems to be valid.
>
> Of course, working around bugs in Valgrind may be a useful thing to do for
> now ... that code is seriously terrifying stuff. And I thought Wine was
> scary :)
> Dan
> there were some late fixes in valgrind about bit manipulation insn:s 
> (yesterday or so IIRC). This could be related. You may want to check out 
> valgrind's svn.
> A+

-- 
Eric Pouech

Quiet valgrind warnings in init_current_teb

On Sat, May 13, 2006 at 11:11:50PM +0100, Mike Hearn wrote:
> if ((ent->HighWord.Bits.Granularity = (limit >= 0x100000)))
>
> but unless I'm reading it wrong this is not testing ent before
> initialization at all, it's testing limit, assigning to ent, then
> testing the result of that assignment ... which seems to be valid.
> Of course it is testing "ent" by accessing a member of it, thus
> dereferencing it.

Leslie

-- 
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Quiet valgrind warnings in init_current_teb

[Mike Hearn]

On 5/14/06, leslie.polzer(a)gmx.net <leslie.polzer(a)gmx.net> wrote:
> Of course it is testing "ent" by accessing a member of it, thus
> dereferencing it.

ent is initialized here OK, it's correctly pointing to an LDT_ENTRY
struct on the stack. Valgrind is (presumably) complaining about
ent->HighWord.Bits.Granularity being tested before being assigned, but
that's wrong and is either a mistake in:

a) My thinking (quite likely)
b) Valgrind
c) GCC

thanks -mike

Quiet valgrind warnings in init_current_teb

[Alexandre Julliard]

"Mike Hearn" <mike(a)plan99.net> writes:
> ent is initialized here OK, it's correctly pointing to an LDT_ENTRY
> struct on the stack. Valgrind is (presumably) complaining about
> ent->HighWord.Bits.Granularity being tested before being assigned, but
> that's wrong and is either a mistake in:
>
> a) My thinking (quite likely)
> b) Valgrind
> c) GCC

It's a valgrind bug. There are some uninitialized bits in the
variable, but the bit that the code is testing is initialized
properly.

-- 
Alexandre Julliard
julliard(a)winehq.org