Memory freeing error around of CRS (?) or other encapsulated PROJ C++ code

[mkgrgis]

Hello, PROJ team!

I am C RDBMS developer. We are working on online SpatiaLite ↔ PostGIS data processing in pgspider/sqlite_fdw#96. Both of SpatiaLite and PostGIS uses PROJ and we are observing some problem which is encapsulated for our code, but points to /usr/lib64/libproj.so.15.3.2.

Example of problem

Our problem have image of memory freeing error in PostgreSQL context, see end of
pgspider/sqlite_fdw#96 (comment) and core dump from next message pgspider/sqlite_fdw#96 (comment)

A "Minimal, Complete and Verifiable Example"

We are using C code, borrowed from SpatiaLite and confirmed by SpatiaLite author. See

1. Add initial SpatiaLite ↔ PostGIS support pgspider/sqlite_fdw#96 (comment)
2. Add initial SpatiaLite ↔ PostGIS support pgspider/sqlite_fdw#96 (comment)

Also there is tested by SpatiaLite author code
pgspider/sqlite_fdw#96 (comment)

Our code placed at https://github.com/mkgrgis/sqlite_fdw/blob/postgis_2_5_0/sqlite_gis.c , especially https://github.com/mkgrgis/sqlite_fdw/blob/e81617aafeeed42f917d0711e745da745a4222bf/sqlite_gis.c#L225 No direct PROJ usage.

Problem description

• Add initial SpatiaLite ↔ PostGIS support pgspider/sqlite_fdw#96 (comment)
• core dump from next message Add initial SpatiaLite ↔ PostGIS support pgspider/sqlite_fdw#96 (comment)

Memory freeing error in PostgreSQL context , pointed to some code near CRS C++ destructors and/or UnitOfMeasure. Both of PostGIS and SpatiaLite uses libproj.

Expected Output

No memory freeing error.

Environment Information

Our environment:
Rocky Linux 8.12, Postgres 17.0, Postgis 3.4.2, SpatiaLite 5.0.1
PostgreSQL select regexp_split_to_table(postgis_full_version, '\"\s+')||'"' component from postgis_full_version(); gives

 POSTGIS="3.4.2 c19ce56"
 [EXTENSION] PGSQL="160"
 GEOS="3.10.2-CAPI-1.16.0"
 PROJ="9.0.0 NETWORK_ENABLED=OFF URL_ENDPOINT=https://cdn.proj.org USER_WRITABLE_DIRECTORY=/home/vagrant/.local/share/proj DATABASE_PATH=/usr/local/share/proj/proj.db"
 GDAL="GDAL 3.5.0alpha1, released 2022/99/99"
 LIBXML="2.9.7"
 TOPOLOGY RASTER"
(7 rows)

• PROJ version (proj) 9.0.0
• Operation System Information Rocky Linux 8.12

Installation method

• libproj installed from OS repo, no compilation from source code
• PostgreSQL + SQLite + SQLite FDW +PostGIS was compiled from C source code according compilation process similar to https://github.com/pgspider/sqlite_fdw/blob/master/.github/workflows/CI.yml for Ubuntu, but adopted to RockyLinux package names.

[rouault]

I'm pretty sure the core of the issue is that in the same process you get 2 copies of libproj, one comping from the OS repo, and the one you built. This isn't a PROJ bug but an integration issue.

You could potentially built the non-system PROJ with
CFLAGS="-DPROJ_RENAME_SYMBOLS -O2"
CXXFLAGS="-DPROJ_RENAME_SYMBOLS -DPROJ_INTERNAL_CPP_NAMESPACE -O2"
and make sure those flags are used too when building a library that includes it.

[mkgrgis]

Thanks, @rouault ! We have no experience around such integration bugs. Your answer was very helpful!