Examples of errors detected by the V774 diagnostic

V774. Pointer was used after the memory was released.

Augeas

V774 The 'child' pointer was used after the memory was reallocated. augtool.c 151

static char *readline_path_generator(const char *text, int state)
{
  ....
  if (ctx != NULL) {
    char *c = realloc(child, strlen(child)-strlen(ctx)+1);  // <=
    if (c == NULL)
      return NULL;
    int ctxidx = strlen(ctx);
    if (child[ctxidx] == SEP)                               // <=
      ctxidx++;
    strcpy(c, &child[ctxidx]);                              // <=
    child = c;
  }
  ....
}

Similar errors can be found in some other places:

• V774 The 'child' pointer was used after the memory was reallocated. augtool.c 153

Bind

V774 The 'res' pointer was used after the memory was released. sample-request.c 225

int
main(int argc, char *argv[]) {
  ....
  struct addrinfo hints, *res;
  ....
  gaierror = getaddrinfo(argv[0], "53", &hints, &res);
  ....
  memmove(&sa.type, res->ai_addr, res->ai_addrlen);
  freeaddrinfo(res);                                    // <=
  sa.length = (unsigned int)res->ai_addrlen;            // <=
  ....
}

Similar errors can be found in some other places:

• V774 The 'res' pointer was used after the memory was released. sample-update.c 193
• V774 The 'res' pointer was used after the memory was released. sample-update.c 217

ICU

V774 CWE-416 The 'mzMappings' pointer was used after the memory was released. zonemeta.cpp 713

UVector*
ZoneMeta::createMetazoneMappings(const UnicodeString &tzid) {
  UVector *mzMappings = NULL;
  ....
  if (U_SUCCESS(status)) {
    ....
    if (U_SUCCESS(status)) {
      ....
      while (ures_hasNext(rb)) {
        ....
        if (mzMappings == NULL) {
          mzMappings = new UVector(
            deleteOlsonToMetaMappingEntry, NULL, status);
          if (U_FAILURE(status)) {
            delete mzMappings;
            uprv_free(entry);
            break;
          }
        }
        ....
      }
      ....
    }
  }
  ures_close(rb);
  return mzMappings;
}

Code is complicated and I find it difficult to say exactly, if there is a bug or not. But it seems to me, it is possible that this function will return a pointer to the memory block being freed.

Qalculate!

V774 The 'cu' pointer was used after the memory was released. Calculator.cc 3595

MathStructure Calculator::convertToBestUnit(....)
{
  ....
  CompositeUnit *cu = new CompositeUnit("", "....");
  cu->add(....);
  Unit *u = getBestUnit(cu, false, eo.local_currency_conversion);
  if(u == cu) {
    delete cu;                                   // <=
    return mstruct_new;
  }
  delete cu;                                     // <=
  if(eo.approximation == APPROXIMATION_EXACT &&
     cu->hasApproximateRelationTo(u, true)) {    // <=
    if(!u->isRegistered()) delete u;
    return mstruct_new;
  }
  ....
}

Haiku Operation System

V774 The 'device' pointer was used after the memory was released. xhci.cpp 1572

void
XHCI::FreeDevice(Device *device)
{
  uint8 slot = fPortSlots[device->HubPort()];
  TRACE("FreeDevice() port %d slot %d\n", device->HubPort(), slot);

  // Delete the device first, so it cleans up its pipes and tells us
  // what we need to destroy before we tear down our internal state.
  delete device;

  DisableSlot(slot);
  fDcba->baseAddress[slot] = 0;
  fPortSlots[device->HubPort()] = 0;
  delete_area(fDevices[slot].trb_area);
  delete_area(fDevices[slot].input_ctx_area);
  delete_area(fDevices[slot].device_ctx_area);

  memset(&fDevices[slot], 0, sizeof(xhci_device));
  fDevices[slot].state = XHCI_STATE_DISABLED;
}

Similar errors can be found in some other places:

• V774 The 'self' pointer was used after the memory was released. TranslatorRoster.cpp 884
• V774 The 'string' pointer was used after the memory was released. RemoteView.cpp 1269
• V774 The 'bs' pointer was used after the memory was released. mkntfs.c 4291
• And 2 additional diagnostic messages.

MuseScore

V774 The 'slur' pointer was used after the memory was released. importgtp-gp6.cpp 2592

void GuitarPro6::readGpif(QByteArray* data)
{
  ....
  if (c) {
    slur->setTick2(c->tick());
    score->addElement(slur);
    legatos[slur->track()] = 0;
  } else {
    delete slur;
    legatos[slur->track()] = 0;
  }
  ....
}