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Stop false positive in clang array OOB sanitiser #1395

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Merged
Aidan63 merged 2 commits into from
Sep 10, 2026
Merged

Stop false positive in clang array OOB sanitiser #1395

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cfe6380
1D array for row data
Sep 10, 2026
6eff436
mRow rename and add row helper function
Sep 10, 2026
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36 changes: 20 additions & 16 deletions src/hx/gc/Immix.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -624,10 +624,14 @@ union BlockData
BlockIdType mId;

// First 2/4 rows contain a byte-flag-per-row
unsigned char mRowMarked[IMMIX_LINES];
unsigned char mRowMarked[IMMIX_LINES];
// Row data as union - don't use first 2/4 rows
unsigned char mRow[IMMIX_LINES][IMMIX_LINE_LEN];
unsigned char mData[IMMIX_LINES * IMMIX_LINE_LEN];

inline unsigned char* row(size_t r)
{
return mData + (r * IMMIX_LINE_LEN);
}
};

struct BlockDataStats
Expand Down Expand Up @@ -1031,7 +1035,7 @@ struct BlockDataInfo
unsigned int &starts = allocStart[r];
if (starts)
{
unsigned int *headerPtr = ((unsigned int *)mPtr->mRow[r]);
unsigned int* headerPtr{ reinterpret_cast<unsigned int*>(mPtr->row(static_cast<size_t>(r))) };
#define CHECK_FLAG(i,byteMask) \
{ \
unsigned int mask = 1<<i; \
Expand Down Expand Up @@ -1145,7 +1149,7 @@ struct BlockDataInfo
// When known to be an actual object start...
AllocType GetAllocTypeChecked(uintptr_t inOffset, bool allowPrevious) const
{
unsigned char time{ mPtr->mRow[0][inOffset + HX_ENDIAN_MARK_ID_BYTE_HEADER] };
unsigned char time{ mPtr->mData[inOffset + HX_ENDIAN_MARK_ID_BYTE_HEADER] };
if (((time + 1) & MARK_BYTE_MASK) != (gByteMarkID & MARK_BYTE_MASK))
{
// Object is either out-of-date, or already marked....
Expand All @@ -1155,10 +1159,10 @@ struct BlockDataInfo
if (!allowPrevious)
return allocNone;

if (*reinterpret_cast<unsigned int *>(mPtr->mRow[0] + inOffset) & IMMIX_ALLOC_IS_CONTAINER)
if (*reinterpret_cast<unsigned int *>(mPtr->mData + inOffset) & IMMIX_ALLOC_IS_CONTAINER)
{
// See if object::new has been called, but not constructed yet ...
void** vtable{ reinterpret_cast<void**>(mPtr->mRow[0] + inOffset + sizeof(int)) };
void** vtable{ reinterpret_cast<void**>(mPtr->mData + inOffset + sizeof(int)) };
if (nullptr == vtable[0])
{
// GCLOG("Partially constructed object.");
Expand Down Expand Up @@ -1199,7 +1203,7 @@ struct BlockDataInfo
while(scan<=inOffset)
{
// Trace along the hole...
unsigned int header{ *reinterpret_cast<unsigned int*>(mPtr->mRow[0] + scan) };
unsigned int header{ *reinterpret_cast<unsigned int*>(mPtr->mData + scan) };
unsigned int size{
!(header & 0xff000000)
? (header & 0x0000ffff)
Expand All @@ -1216,13 +1220,13 @@ struct BlockDataInfo

if (nullptr != outPtr)
{
*outPtr = reinterpret_cast<uintptr_t>(mPtr->mRow[0] + scan + sizeof(int));
*outPtr = reinterpret_cast<uintptr_t>(mPtr->mData + scan + sizeof(int));
}

if (header & IMMIX_ALLOC_IS_CONTAINER)
{
// See if object::new has been called, but not constructed yet ...
void **vtable = (void **)(mPtr->mRow[0] + scan + sizeof(int));
void **vtable{ reinterpret_cast<void **>(mPtr->mData + scan + sizeof(int)) };
if (vtable[0]==0)
{
// GCLOG("Partially constructed object.");
Expand Down Expand Up @@ -1301,7 +1305,7 @@ struct BlockDataInfo
{
if (nullptr != outPtr)
{
*outPtr = reinterpret_cast<uintptr_t>(mPtr->mRow[0] + blockOffset + sizeof(int));
*outPtr = reinterpret_cast<uintptr_t>(mPtr->mData + blockOffset + sizeof(int));
}

return result;
Expand Down Expand Up @@ -1334,10 +1338,10 @@ struct BlockDataInfo
{
if (rowMarked[r])
{
unsigned int starts = allocStart[r];
unsigned int starts{ allocStart[r] };
if (!starts)
continue;
unsigned char *row = mPtr->mRow[r];
unsigned char* row{ mPtr->row(static_cast<size_t>(r)) };
for(int i=0;i<32;i++)
{
int pos = i<<2;
Expand Down Expand Up @@ -3754,8 +3758,8 @@ class GlobalAllocator
{
if ( starts & (1<<i))
{
unsigned int *row = (unsigned int *)from->mPtr->mRow[r];
unsigned int &header = row[i];
unsigned int* row{ reinterpret_cast<unsigned int*>(from->mPtr->row(static_cast<size_t>(r))) };
unsigned int &header{ row[i] };

if ((header&IMMIX_ALLOC_MARK_ID) == hx::gMarkID)
{
Expand Down Expand Up @@ -3964,8 +3968,8 @@ class GlobalAllocator
for(int loc=0;loc<32;loc++)
if (startFlags & (1<<loc))
{
unsigned int *row = (unsigned int *)from->mPtr->mRow[r];
unsigned int &header = row[loc];
unsigned int* row{ reinterpret_cast<unsigned int*>(from->mPtr->row(static_cast<size_t>(r))) };
unsigned int &header{ row[loc] };

if ((header&IMMIX_ALLOC_MARK_ID) == hx::gMarkID)
{
Expand Down
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