[Bug c++/92001] New: missing -Wclass-memaccess with array as first argument to memset

[sbergman at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92001

            Bug ID: 92001
           Summary: missing -Wclass-memaccess with array as first argument
                    to memset
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sbergman at redhat dot com
                CC: msebor at gcc dot gnu.org
  Target Milestone: ---

With at least both GCC 9.2.1 and recent trunk towards GCC 10,

  #include <cstring>
  struct S { S(); };
  void f() {
    S s[1];
    std::memset(s, 0, sizeof s);
  }

does not emit a -Wclass-memaccess (but it does when you change s to be of
non-array type).

(See
<https://gerrit.libreoffice.org/plugins/gitiles/core/+/d03041e19215592f21ba1222d3cfa29e1f94260a%5E%21>
"Drop bogus memsets" for a real-life case of such a false negative.  There were
about half a dozen similar cases across the LibreOffice code base.)