[Bug other/80049] New: gcc/genmodes.c: PVS-Studio: NULL Pointer Dereference (CWE-476)

[khandeliants at viva64 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80049

            Bug ID: 80049
           Summary: gcc/genmodes.c: PVS-Studio: NULL Pointer Dereference
                    (CWE-476)
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: khandeliants at viva64 dot com
  Target Milestone: ---

We have found a weakness (CWE-476) using PVS-Studio tool. PVS-Studio is a
static code analyzer for C, C++ and C#: https://www.viva64.com/en/pvs-studio/

Analyzer warning: V595 The 'm->component' pointer was utilized before it was
verified against nullptr. Check lines: 399, 407. genmodes.c 399

static void complete_mode (struct mode_data *m)
{
  ....
  if (   m->cl == MODE_COMPLEX_INT 
      || m->cl == MODE_COMPLEX_FLOAT)
    alignment = m->component->bytesize;        // <=
  else
    alignment = m->bytesize;

  m->alignment = alignment & (~alignment + 1);

  if (m->component)                            // <=
    {
      m->next_cont = m->component->contained;
      m->component->contained = m;
    }
}