Segfault from _RegisterMissingFaces

[strk]

I'm getting a segfault from a draft implementation of TopoGeo_addGeometry which is pure plpgsql and shows the segfault happens when calling the internal _RegisterMissingFaces function which is instead written in C.

The C function is only accessible from 3.5.0dev (still unreleased) so I'm marking this as a blocker to avoid shipping a crashable version.

[Sandro Santilli <strk@…>]

In a6194d2/git:

Move topology polygonizer code in its own file

References #5684

[strk]

Instructions to reproduce:

1. Download the attached issue5684.pgtopo
2. Import with: pgtopo_import -f issue5684.pgtopo issue5684 | psql postgis_reg
3. select topology._registermissingfaces('issue5684'); -- 3 times

Here's the dance performance:

strk=# select topology._registermissingfaces('issue5684');
ERROR:  Polygonize: face table is not empty.
strk=# select topology._registermissingfaces('issue5684');
ERROR:  Polygonize: face table is not empty.
strk=# select topology._registermissingfaces('issue5684');
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
The connection to the server was lost. Attempting reset: Failed.
!?> 

[Sandro Santilli <strk@…>]

In 56023cc/git:

Always initialize the mbr member of fetched faces

Closes #5684

[strk]

The fixing change was too wide in scope, introducing bug #5707. The change was reverted with [943215120c9fe63de0523f9560ca6a1a44e329aa/git] so I'm reopening this ticket as the fix needs to be somewhere else

[Sandro Santilli <strk@…>]

In 9eefe39/git:

Do not attempt to release non-allocated face MBR

Fixes crash in _RegisterMissingFaces internal function
Closes #5684