Examples of errors detected by the V642 diagnostic

V642. Function result is saved inside the 'byte' type variable. Significant bits may be lost. This may break the program's logic.

Xpdf

V642 Saving the 'memcmp' function result inside the 'char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. bitmapoutputdev.cc 710

GBool BitmapOutputDev::clip0and1differ(....)
{
  ....
  char differs2 = memcmp(a0, a1, width*height);
  if(differs && !differs2)
    msg("<warning> Strange internal error (2)");
  ....
}

ReactOS

V642 Saving the 'memcmp' function result inside the 'unsigned short' type variable is inappropriate. The significant bits could be lost breaking the program's logic. recyclebin.cpp 542

HRESULT WINAPI CRecycleBin::CompareIDs(....)
{
  ....
  return MAKE_HRESULT(SEVERITY_SUCCESS, 0,
   (unsigned short)memcmp(pidl1->mkid.abID,
                          pidl2->mkid.abID,
                          pidl1->mkid.cb));
}

Firebird

V642 Saving the 'memcmp' function result inside the 'short' type variable is inappropriate. The significant bits could be lost breaking the program's logic. texttype.cpp 338

SSHORT TextType::compare(ULONG len1, const UCHAR* str1,
                         ULONG len2, const UCHAR* str2)
{
  ....
  SSHORT cmp = memcmp(str1, str2, MIN(len1, len2));

  if (cmp == 0)
    cmp = (len1 < len2 ? -1 : (len1 > len2 ? 1 : 0));

  return cmp;

}

Similar errors can be found in some other places:

• V642 Saving the 'memcmp' function result inside the 'short' type variable is inappropriate. The significant bits could be lost breaking the program's logic. cvt2.cpp 256
• V642 Saving the 'memcmp' function result inside the 'short' type variable is inappropriate. The significant bits could be lost breaking the program's logic. cvt2.cpp 522

Linux Kernel

V642 Saving the 'memcmp' function result inside the 'unsigned char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. zatm.c 1168

static unsigned char eprom_try_esi(
  struct atm_dev *dev, unsigned short cmd,
  int offset, int swap)
{
  unsigned char buf[ZEPROM_SIZE];
  struct zatm_dev *zatm_dev;
  int i;

  zatm_dev = ZATM_DEV(dev);
  for (i = 0; i < ZEPROM_SIZE; i += 2) {
    eprom_set(zatm_dev,ZEPROM_CS,cmd); /* select EPROM */
    eprom_put_bits(zatm_dev,ZEPROM_CMD_READ,ZEPROM_CMD_LEN,cmd);
    eprom_put_bits(zatm_dev,i >> 1,ZEPROM_ADDR_LEN,cmd);
    eprom_get_byte(zatm_dev,buf+i+swap,cmd);
    eprom_get_byte(zatm_dev,buf+i+1-swap,cmd);
    eprom_set(zatm_dev,0,cmd); /* deselect EPROM */
  }
  memcpy(dev->esi,buf+offset,ESI_LEN);
  return memcmp(dev->esi,"\0\0\0\0\0",ESI_LEN);
}

Linux Kernel

V642 Saving the 'memcmp' function result inside the 'unsigned char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. host.c 1846

void sci_controller_power_control_queue_insert(....)
{
  ....
  for (i = 0; i < SCI_MAX_PHYS; i++) {
    u8 other;
    current_phy = &ihost->phys[i];

    other = memcmp(current_phy->frame_rcvd.iaf.sas_addr,
                   iphy->frame_rcvd.iaf.sas_addr,
                   sizeof(current_phy->frame_rcvd.iaf.sas_addr));

    if (current_phy->sm.current_state_id == SCI_PHY_READY &&
        current_phy->protocol == SAS_PROTOCOL_SSP &&
        other == 0) {
      sci_phy_consume_power_handler(iphy);
      break;
    }
  }
  ....
}

Similar errors can be found in some other places:

• V642 Saving the 'memcmp' function result inside the 'unsigned char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. zatm.c 1168
• V642 Saving the 'memcmp' function result inside the 'unsigned char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. host.c 1789

OpenToonz

V642 Saving the '_wcsicmp' function result inside the 'char' type variable is inappropriate. The significant bits could be lost, breaking the program's logic. tfilepath.cpp 328

bool TFilePath::operator<(const TFilePath &fp) const
{
  ....
  char differ;
  differ = _wcsicmp(iName.c_str(), jName.c_str());
  if (differ != 0)
    return differ < 0 ? true : false;
  ....
}

Firebird

V642 Saving the 'memcmp' function result inside the 'short' type variable is inappropriate. The significant bits could be lost breaking the program's logic. texttype.cpp 3

SSHORT TextType::compare(ULONG len1, const UCHAR* str1,
                         ULONG len2, const UCHAR* str2)
{
  ....
  SSHORT cmp = memcmp(str1, str2, MIN(len1, len2));

  if (cmp == 0)
    cmp = (len1 < len2 ? -1 : (len1 > len2 ? 1 : 0));

  return cmp;
}

Linux Kernel

V642 Saving the 'memcmp' function result inside the 'unsigned char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. host.c 1789

static void power_control_timeout(unsigned long data)
{
  ....
  u8 other = memcmp(requester->frame_rcvd.iaf.sas_addr,
                    iphy->frame_rcvd.iaf.sas_addr,
                    sizeof(requester->frame_rcvd.iaf.sas_addr));

  if (other == 0) {
    ....
  }
  ....
}

Tizen

V642 Saving the 'strcmp' function result inside the 'unsigned char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. grid.c 137

typedef unsigned char Eina_Bool;

static Eina_Bool _state_get(
  void *data, Evas_Object *obj, const char *part)
{
  ....
  if (!strcmp(part, STATE_BROWSER))
    return !strcmp(id, APP_ID_BROWSER);
  else if (!strcmp(part, STATE_NOT_BROWSER))
    return strcmp(id, APP_ID_BROWSER);                 // <=

  return EINA_FALSE;
}

It seems to me, in this code fragment, the negation operator '!' is missing.

Amazon FreeRTOS

V642 [CWE-197] Saving the 'strncmp' function result inside the 'short' type variable is inappropriate. The significant bits could be lost breaking the program's logic. aws_greengrass_discovery.c 637

/* Return true if the string " pcString" is found
 * inside the token pxTok in JSON file pcJson. */
static BaseType_t prvGGDJsoneq( const char * pcJson,
                                const jsmntok_t * const pxTok,
                                const char * pcString )
{
  ....
  BaseType_t xStatus = pdFALSE;

  if( ( int16_t ) strncmp( &pcJson[ pxTok->start ], // <=
                           pcString,
                           ulStringSize ) == 0 )
  {
    xStatus = pdTRUE;
  }

  ....

  return xStatus;
}

Espressif IoT Development Framework

V642 Saving the 'memcmp' function result inside the 'unsigned char' type variable is inappropriate. The significant bits could be lost breaking the program's logic. mbc_tcp_master.c 387

static esp_err_t mbc_tcp_master_set_request(
  char* name, mb_param_mode_t mode, mb_param_request_t* request,
  mb_parameter_descriptor_t* reg_data)
{
  ....
  // Compare the name of parameter with parameter key from table
  uint8_t comp_result = memcmp((const char*)name,
                               (const char*)reg_ptr->param_key,
                               (size_t)param_key_len);
  if (comp_result == 0) {
  ....
}