Code bug revealed by MinGW64 - crash caused by raster GUC define after CREATE EXTENSION

[manaeem]

I am using PostGIS 2.2.3 (​http://download.osgeo.org/postgis/source/postgis-2.2.3.tar.gz) with MinGW64, It is failing with "0xC0000005: Access violation reading location 0x0000000029C6AD70" exception.

test=# create extension postgis;
CREATE EXTENSION
test=# select * from pg_settings;
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.

---

>? values
0x000000000042cf20 {0x0000000028c80af0 "postgis.gdal_enabled_drivers", 0x0000000029b7bee0 "DISABLE_ALL", ...}
    [0]: 0x0000000028c80af0 "postgis.gdal_enabled_drivers"
    [1]: 0x0000000029b7bee0 "DISABLE_ALL"
    [2]: 0x0000000000000000 <NULL>
    [3]: 0x00000001405ae0b8 "Customized Options"
    [4]: 0x000000006b806221 "Enabled GDAL drivers."
    [5]: 0x000000006b806190 "List of enabled GDAL drivers by short name. To enable/disable all drivers, use 'ENABLE_ALL' or 'DISABLE_ALL' (sets the GDAL_SKIP config option)."
    [6]: 0x000000014048d660 "superuser"
    [7]: 0x0000000140551274 "string"
    [8]: 0x0000000140492ce8 "default"
    [9]: 0x0000000000000000 <NULL>
    [10]: 0x0000000000000000 <NULL>
    [11]: 0x0000000000000000 <NULL>
    [12]: 0x0000000000000000 <NULL>
    [13]: 0x00000000008a21a0 ""
    [14]: 0x0000000000000000 <NULL>
    [15]: 0x0000000000000000 <NULL>
    [16]: 0x00000000008a21a0 ""

Issue seems reproducible in PostGIS version 2.3 and 2.4 as well. backend process is crashing while processing bootValue define done by PostGIS extension i.e.

raster/rt_pg/rtpostgis.c

        DefineCustomStringVariable(
                "postgis.gdal_enabled_drivers", /* name */
                "Enabled GDAL drivers.", /* short_desc */
                "List of enabled GDAL drivers by short name. To enable/disable all drivers, use 'ENABLE_ALL' or 'DISABLE_ALL' (sets the GDAL_SKIP config option).", /* long_desc */
                &gdal_enabled_drivers, /* valueAddr */
                boot_postgis_gdal_enabled_drivers, /* bootValue */
                PGC_SUSET, /* GucContext context */
                0, /* int flags */
#if POSTGIS_PGSQL_VERSION >= 91
                NULL, /* GucStringCheckHook check_hook */
#endif
                rtpg_assignHookGDALEnabledDrivers, /* GucStringAssignHook assign_hook */
                NULL  /* GucShowHook show_hook */
        );

boot_postgis_gdal_enabled_drivers is allocated on CurrentMemoryContext via palloc() in related extension initialization routine (_PG_init), instead it is appropriate to utilize TopMemoryContext instead. PFA patch with it, crash is no more reproducible with it. Thanks.

[robe]

In 15208:

raster GUC - boot_postgis_gdal_enabled_drivers should use TopMemoryContext instead of CurrentMemoryContext
References #3659 for trunk (PostGIS 2.4)

[robe]

In 15209:

raster GUC - boot_postgis_gdal_enabled_drivers should use TopMemoryContext instead of CurrentMemoryContext
References #3659 for 2.3 (PostGIS 2.3.4) patch provided by manaeem

[robe]

In 15210:

raster GUC - boot_postgis_gdal_enabled_drivers should use TopMemoryContext instead of CurrentMemoryContext
Closes #3659 for 2.2 (PostGIS 2.2.4) patch provided by manaeem