Re: Windows warnings from VS 2017

On Thu, Sep 21, 2017 at 12:26 PM, Andrew Dunstan <
andrew(dot)dunstan(at)2ndquadrant(dot)com> wrote:

>
>
> On 09/20/2017 08:18 PM, Andrew Dunstan wrote:
> >
> > On 09/20/2017 07:54 PM, Tom Lane wrote:
> >> Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> writes:
> >>> It's also warning that it will copy 16 bytes to a 13 byte structure at
> >>> lines 518, 1293 and 1294 of src/backend/commands/dbcommands.c. I
> haven't
> >>> seen any ill effects of this so far, but it seems to indicate that
> >>> something is possibly amiss on this compiler with the MemSet macros.
> >> That's weird. Is it too stupid to figure out that the if() inside
> >> MemSet evaluates to constant false in these calls? It seems hard to
> >> see how it would realize that the loop will write 16 bytes if it doesn't
> >> propagate the constant value forward.
> >>
> >> However ... on some other compilers, I've noticed that the compiler
> seems
> >> more likely to make "obvious" deductions of that sort if the variables
> in
> >> question are marked const. Does it help if you do
> >>
> >> - void *_vstart = (void *) (start); \
> >> - int _val = (val); \
> >> - Size _len = (len); \
> >> + void * const _vstart = (void *) (start); \
> >> + const int _val = (val); \
> >> + const Size _len = (len); \
> >>
> >>
> >> I don't think there's any strong reason not to just do s/MemSet/memset/
> >> in these calls and nearby ones, but it would be good to understand just
> >> what's wrong here. And why it's only showing up in that file; seems
> >> nearly certain that we have similar coding elsewhere.
> >>
> >>
> >
> > I'll test it.
> >
>
>
> Doesn't make a difference. I agree it would be good to understand what's
> going on.

These warnings are not produced when the build is run in DEBUG mode.
Because of this I didn't see these warning when I was working with VS 2017.

This may be an issue with VS 2017 compiler.

Regards,
Hari Babu
Fujitsu Australia