[Bug c++/87427] -Wclass-memaccess improvement for POD with convenience initializer

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87427

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |msebor at gcc dot gnu.org
         Resolution|---                         |WONTFIX

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
A common C idiom is

  struct S *p = (struct S*)malloc (sizeof *p);
  memset (p, 0, sizeof *p);

When such code is being ported to C++, or when C programmers are writing
analogous code in C++, it's not unusual to make the mistake of assuming that
the same code will work unchanged even when struct S has a default constructor
(or forget that it does, or add one and forget to change the dynamic
initialization).  That's not the case with a struct like the one in the example
in comment #0, and the warning helps detect this mistake.  We would not want to
weaken the warning to prevent detecting it.

In our view, memset (and other raw memory functions) are low-level primitives
designed for manipulating object representation at the byte level.  They should
not be used with higher-level abstractions.  The preferred way to initialize
objects of non-trivial types is by using their ctors, and that's what the
warning is meant to encourage.