Re: Expand palloc/pg_malloc API

Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> writes:
> On Tue, May 17, 2022 at 5:11 PM Peter Eisentraut
> <peter(dot)eisentraut(at)enterprisedb(dot)com> wrote:
>> This adds additional variants of palloc, pg_malloc, etc. that
>> encapsulate common usage patterns and provide more type safety.

> I see lots of instances where there's no explicit type-casting to the
> target variable type -
> retval = palloc(sizeof(GISTENTRY));
> Interval *p = palloc(sizeof(Interval));
> macaddr *v = palloc0(sizeof(macaddr)); and so on.

Yeah. IMO the first of those is very poor style, because there's
basically nothing enforcing that you wrote the right thing in sizeof().
The others are a bit safer, in that at least a human can note that
the two types mentioned on the same line match --- but I doubt any
compiler would detect it if they don't. Our current preferred style

Interval *p = (Interval *) palloc(sizeof(Interval));

is really barely an improvement, because only two of the three types
mentioned are going to be checked against each other.

So I think Peter's got a good idea here (I might quibble with the details
of some of these macros). But it's not really going to move the
safety goalposts very far unless we make a concerted effort to make
these be the style everywhere. Are we willing to do that? What
will it do to back-patching difficulty? Dare I suggest back-patching
these changes?

regards, tom lane