How to resolve this C6385 code analysis warning: Reading invalid data - c++

Question

I am trying to address a code analysis warning that appears in the following method:
CStringArray* CCreateReportDlg::BuildCustomAssignArray(ROW_DATA_S &rsRowData)
{
INT_PTR iAssign, iNumAssigns, iUsedAssign;
CStringArray *pAryStrCustom = nullptr;
CUSTOM_ASSIGN_S *psAssign = nullptr;
if (rsRowData.uNumCustomToFill > 0)
{
pAryStrCustom = new CStringArray[rsRowData.uNumCustomToFill];
iNumAssigns = m_aryPtrAssign.GetSize();
for (iAssign = 0, iUsedAssign = 0; iAssign < iNumAssigns; iAssign++)
{
psAssign = (CUSTOM_ASSIGN_S*)m_aryPtrAssign.GetAt(iAssign);
if (psAssign != nullptr)
{
if (!psAssign->bExcluded)
{
pAryStrCustom[iUsedAssign].Copy(psAssign->aryStrBrothersAll);
iUsedAssign++;
}
}
}
}
return pAryStrCustom;
}
The offending line of code is:
pAryStrCustom[iUsedAssign].Copy(psAssign->aryStrBrothersAll);
I compile this code for both 32 bit and 64 bit. The warning being raised is:
Warning (C6385) Reading invalid data from pAryStrCustom: the readable size is (size_t)*40+8 bytes, but 80 bytes may be read.
I don't know if it is relevant, but the CUSTOM_ASSIGN_S structure is defined as:
typedef struct tagCustomAssignment
{
int iIndex;
CString strDescription;
CString strHeading;
BOOL bExcluded;
CStringArray aryStrBrothersAll;
CStringArray aryStrBrothersWT;
CStringArray aryStrBrothersSM;
BOOL bIncludeWT;
BOOL bIncludeTMS;
BOOL bFixed;
int iFixedType;
} CUSTOM_ASSIGN_S;
My code is functional (for years) but is there a coding improvement I can make to address this issue? I have read the linked article and it is not clear to me. I have also seen this question (Reading Invalid Data c6385) along similar lines. But in my code I can't see how that applies.

Answer 1

Warning... the readable size is (size_t)*40+8 bytes, but 80 bytes may be read.
The wording for this warning is not accurate, because size_t is not a number, it's a data type. (size_t)*40+8 doesn't make sense. It's probably meant to be:
Warning... the readable size is '40+8 bytes', but '80 bytes' may be read.
This warning can be roughly reproduced with the following example:
//don't run this code, it's just for viewing the warning
size_t my_size = 1;
char* buf = new char[my_size];
buf[1];
//warning C6385: Reading invalid data from 'buf':
//the readable size is 'my_size*1' bytes, but '2' bytes may be read
The warning is correct and obvious. buf[1] is out of bound. The compiler sees allocation size for buf is my_size*1, and index 1 is accessing byte '2'. I think in other place the compiler prints it incorrectly, but the actual warning is valid.
In any case, just make sure iUsedAssign is within range
if (!psAssign->bExcluded && iUsedAssign < rsRowData.uNumCustomToFill)
{
...
}