Andrew Dunstan <andrew.duns...@2ndquadrant.com> writes: > On 02/23/2017 04:41 PM, Tom Lane wrote: >> The reason this is kind of scary is that it's just blithely assuming >> that the function won't look at the *other* fields of the FmgrInfo. >> If it did, it would likely get very confused, since those fields >> would be describing the GIN support function, not the function we're >> calling. >> >> We could alternatively have this trampoline function set up a fresh, local >> FmgrInfo struct that it zeroes except for copying fn_extra and fn_mcxt >> from the caller's struct, and then it copies fn_extra back again on the >> way out. That's a few more cycles but it would be safer, I think; if the >> function tried to look at the other fields such as fn_oid it would see >> obviously bogus data.
> Do we want one or both of these? I'm prepared to code up a patch to > fmgr.[ch] to provide them. On reflection I'm not sure that the double-copy approach is all that much safer than just passing down the caller's flinfo pointer. Most of the time it would be better, but suppose that the callee updates fn_extra and then throws elog(ERROR) --- the outcome would be different, probably creating a leak in fn_mcxt. Maybe this would still be okay, because perhaps that FmgrInfo is never used again, but I don't think we can assume that for the case at hand. At this point I'd be inclined to just document that the called function should only use fn_extra/fn_mcxt. > I don't know what to call it either. In my test I used > CallerContextFunctionCall2 - not sure if that's quite right, but should > be close. CallerInfo? CallerFInfo? Or we could spell out CallerFmgrInfo but that seems a bit verbose. regards, tom lane -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers