Return unsigned char as a hex value - c++

Question

I'm aiming to be able to return unsigned char as a hex values, this is so I can pass the value from my client to server side.
How my data is generated before trying to be converted into hex:
unsigned char *TestClass::GetKey()
{
// Generate a key of length 32 bytes
memset(this->szKey, 0, 32);
RAND_bytes(this->szKey, 32);
return this->szKey;
}
This what i've currently got so far:
TestClass myTestClass;
void CJSCallDoc::OnDocumentComplete(LPCTSTR strURL,LPDISPATCH pDisp)
{
unsigned char szKey = hex_print(myTestClass.GetKey());
}
unsigned char CJSCallDoc::hex_print(unsigned char* pv)
{
unsigned char *p = pv;
if (NULL == pv)
{
return NULL;
}
else
{
char storedString[256];
size_t len = strlen((const char*)pv);
size_t i = 0;
for (; i < len; ++i)
{
strcpy_s(storedString, 256, "Test");
strcat_s(storedString, reinterpret_cast<char*>(*p++));
}
return *storedString;
}
}
The problem I'm having is with this line:
strcat_s(storedString, reinterpret_cast<char*>(*p++));
This line causes my application to crash and this is the following error I get:
Unhandled exception at 0x01664467 in TestApp.exe: 0xC0000005: Access
violation reading location 0x000000FE.
and the error takes me to tcscat_s.inl:
---> while ((*p++ = *_SRC++) != 0 && --available > 0)
{
}
However when I try and do the following it works fine:
unsigned char CJSCallDoc::hex_print(unsigned char* pv)
{
unsigned char *p = pv;
if (NULL == pv)
{
return NULL;
}
else
{
char storedString[256];
size_t len = strlen((const char*)pv);
size_t i = 0;
for (; i < len; ++i)
{
strcpy_s(storedString, 256, "Test");
strcat_s(storedString, "WORKS");
}
return *storedString;
}
}
Could someone explain to me, what I'm doing wrong and give me some advice in the right direction?

Answer 1

The problem is that you are casting your data to address, in:
strcat_s(storedString, reinterpret_cast<char*>(*p++));
*p++ is equal to whatever your string contains - first element is p from your example, so you are casting this p - decimal value 112, to char*. strcat_s will try to read string from this location which immediately ends with segfault.