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c++charuuidreinterpret-castunsigned-char

reinterpret_cast on pointers pitfall between char and unsigned char?

I'm using the following function in order to create an UUID and write it in a human-readable form into a pre-allocated buffer. Something goes wrong.

void createUUID(char* pDst)
{
    UUID    lUUIDObj;
    UuidCreate(&lUUIDObj);
    unsigned char*  lDest = reinterpret_cast<unsigned char*>(pDst);
    UuidToStringA(&lUUIDObj, &lDest)
}

At the end of the method, the debugger says:

  • lDest = 0x01fe4fd8 "df4a5ed8-c0d2-495a-84d7-ce0e07cf2113"
  • pDst = 0x0012ec7c "ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌ"

I thought that both would have the same content, however it is not the case.

What happened? Thanks.

Solution

  • Looking at the documentation for UuidToStringA, it says:

    The RPC run-time library allocates memory for the string returned in the StringUuid parameter.

    This means that after the call lDest does no longer point to pDst.