[Interest] ASSERT / Debug Crash in Qt 5.3.2. WTF, Windows x64, LLIntData.cpp at bitwise_cast<uint32_t*>(&testVector)[sizeof(void*)/sizeof(uint32_t) + 1] == 42)
Allan Sandfeld Jensen
kde at carewolf.com
Fri Oct 10 16:24:58 CEST 2014
Hi Andre
That all looks reasonable, but what is in castResult[3] ?
It expected to look like this:
void * m_buffer [int index 0-1]
uint m_capacity [int index 2]
int m_size [int index 3]
where m_capacity on Linux is 44, but m_size is 42.
`Allan
On Friday 10 October 2014, Andre Barth wrote:
> Hi Allan,
>
> Thanks for the prompt response. I will go ahead & log a bug.
>
> FWIW - Below is some test output.
>
> Thanks,
> Andre
>
> //some changed test code:
> Vector<int> testVector;
> testVector.resize(42);
>
> auto sizeOfCalc = (sizeof(void*)/sizeof(uint32_t) + 1);
>
> auto address = &testVector;
> auto castResult = bitwise_cast<uint32_t*>(&testVector);
> auto indexedResult = castResult[sizeOfCalc];
>
> bool result = (indexedResult == 42);
>
> //and the corresponding "online" checks & results...
>
> sizeof(void*)
> 0x0000000000000008
>
> sizeof(uint32_t)
> 0x0000000000000004
>
> sizeOfCalc
> 0x0000000000000003
>
> address
> 0x00000000002ce7d8 {m_size=0x0000002a }
> WTF::VectorBuffer<int,0>: {...}
> m_size: 0x0000002a
>
> castResult
> 0x00000000002ce7d8 {0x083f8450}
>
> indexedResult
> 0xcccccccc
>
> castResult[0]
> 0x083f8450
>
> castResult[1]
> 0x00000000
>
> castResult[2]
> 0x0000002a
>
>
> -----Original Message-----
> From: Allan Sandfeld Jensen [mailto:carewolf at gmail.com] On Behalf Of Allan
> Sandfeld Jensen Sent: Friday, October 10, 2014 3:09 PM
> To: interest at qt-project.org
> Cc: Andre Barth
> Subject: Re: [Interest] ASSERT / Debug Crash in Qt 5.3.2. WTF, Windows x64,
> LLIntData.cpp at
> bitwise_cast<uint32_t*>(&testVector)[sizeof(void*)/sizeof(uint32_t) + 1]
> == 42)
>
> On Friday 10 October 2014, Andre Barth wrote:
> > Hi all,
> >
> > I built a JIT-free version of Qt 5.3.2 (Win64) and now run into this
> > assertion in
> >
> > ..\Qt\qtwebkit\Source\JavaScriptCore\llint\LLIntData.cpp
> >
> > Vector<int> testVector;
> > testVector.resize(42);
> > ASSERT(bitwise_cast<uint32_t*>(&testVector)[sizeof(void*)/sizeof(uint3
> > 2_t)+
> >
> > 1] == 42);
> >
> > Here is a bug report / changeset I've found wrt this:
> >
> > http://trac.webkit.org/changeset/148896/trunk/Source/JavaScriptCore/ll
> > int/L
> > LIntData.cpp
> >
> > and
> >
> > https://bugs.webkit.org/show_bug.cgi?id=97268
> >
> > The assert is supposed to check, that the Vector's m_size variable is
> > at the correct address, I guess?!
> >
> > If not, anyone can shed a light on this and explain the purpose of it
> > and where I might have incorrect compilation settings applied?
> >
> > Am I missing somewhere an alignment pragma or something to make this
> > (sizeof(void*)/sizeof(uint32_t))
> > always calculate the right address - regardless of whether its x86 or
> > x64?
>
> There are some differences between alignment and exact types between linux
> x64 and win x64. Could you test what (sizeof(void*)/sizeof(uint32_t)) is,
> and what is on the first few ints of the address of Vector<int> after a
> resize(42)?
>
> Anyway, it might we worth opening a bug for to track the issue. Even if the
> assert turns out to be harmless, the binaries should be able to run in
> debug versions (even win64).
>
> `Allan
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