Re: Change copyObject() to use typeof_unqual

Hi Peter!

On 20.01.2026 10:37, Peter Eisentraut wrote:
> Currently, when the argument of copyObject() is const-qualified, the
> return type is also, because the use of typeof carries over all the
> qualifiers.  This is incorrect, since the point of copyObject() is to
>  make a copy to mutate.  But apparently no code ran into it.

Great change. I've ran into that multiple times and had to
un-const-correct my code because of how copyObject() works.

> The new implementation uses typeof_unqual, which drops the qualifiers,
> making this work correctly.
> 
> typeof_unqual is standardized in C23, but all recent versions of all the
> usual compilers support it even in non-C23 mode, at least as
> __typeof_unqual__.  We add a configure/meson test for typeof_unqual and
> __typeof_unqual__ and use it if it's available, else we use the existing
> fallback of just returning void *.
> 
> (Even MSVC supports it, if we use a slightly newer version than is on
> CI.  For example, the new buildfarm member unicorn would support it.)

I'm not too familiar with the build system, so I let someone else review
this part.

> The second patch make some changes to take advantage of this improved
> qualifier handling.  EventTriggerCollectSimpleCommand() is a good
> example:  It takes a node tree and makes a copy that it keeps around for
> its internal purposes, but it can't communicate via its function
> signature that it promises not scribble on the passed node tree.  That
> is now fixed.

The changes to EvenTriggerCollectSimpleCommand() look good to me.

Are you planning to look at the rest of the code as well? At a quick
glance there seem to be more places that can be changed in similar ways,
e.g. see refresh_matview_datafill().

--
David Geier