Examples of errors detected by the V784 diagnostic

V784. The size of the bit mask is less than the size of the first operand. This will cause the loss of the higher bits.

Perl 5

V784 The size of the bit mask is less than the size of the first operand. This will cause the loss of higher bits. inffast.c 296

void ZLIB_INTERNAL inflate_fast(z_streamp strm, unsigned start)
{
  ....
  unsigned long hold;         /* local strm->hold */
  unsigned bits;              /* local strm->bits */
  ....
  hold &= (1U << bits) - 1;
  ....
}

LLVM/Clang

V784 The size of the bit mask is less than the size of the first operand. This will cause the loss of higher bits. RuntimeDyld.cpp 815

unsigned getStubAlignment() override {
  if (Arch == Triple::systemz)
    return 8;
  else
    return 1;
}

Expected<unsigned>
RuntimeDyldImpl::emitSection(const ObjectFile &Obj,
                             const SectionRef &Section,
                             bool IsCode) {
  ....
  uint64_t DataSize = Section.getSize();
  ....
  if (StubBufSize > 0)
    DataSize &= ~(getStubAlignment() - 1);
  ....
}

Qemu

V784 The size of the bit mask is less than the size of the first operand. This will cause the loss of higher bits. cadence_gem.c 1486

typedef struct CadenceGEMState {
  ....
  uint32_t regs_ro[CADENCE_GEM_MAXREG];
}
....
static void gem_write(void *opaque, hwaddr offset, uint64_t val,
        unsigned size)
{
  ....
  val &= ~(s->regs_ro[offset]);
  ....
}

LLVM/Clang

V784 [CWE-197, CERT-INT31-C] The size of the bit mask is less than the size of the first operand. This will cause the loss of higher bits. Types.h 529

uint64_t NullabilityPayload = 0;

static constexpr const unsigned NullabilityKindMask = 0x3;

void addTypeInfo(unsigned index, NullabilityKind kind) {
  ....
  NullabilityPayload &=
    ~(NullabilityKindMask << (index * NullabilityKindSize));
  ....
}

iSulad

V784 [CWE-197, CERT-INT31-C] The size of the bit mask is less than the size of the first operand. This will cause the loss of higher bits. utils_fs.c 257

struct mount_option_element {
  const char *option;
  bool clear;
  int flag;
};

static void do_parse_mntopt(const char *opt, unsigned long *mflags, char **data)
{
  size_t i = 0;

  for (i = 0; i < sizeof(g_mount_options) / sizeof(g_mount_options[0]); i++) {
    if (strncmp(opt, g_mount_options[i].option,
                strlen(g_mount_options[i].option)) == 0) {
      if (g_mount_options[i].clear) {
        *mflags &= ~g_mount_options[i].flag;
  ....
}