sfcgal legacy test via extension: ERROR: attempt to redefine parameter "postgis.backend

[strk]

cd regress
./run_test.pl -v --sfcgal --extension sfcgal/legacy.sql
...
 sfcgal/legacy .. failed (diff expected obtained: /tmp/pgis_reg/test_1_diff)
-----------------------------------------------------------------------------
--- sfcgal/legacy_expected      2015-03-28 11:16:04.798484842 +0100
+++ /tmp/pgis_reg/test_1_out    2015-05-04 11:57:26.474192034 +0200
@@ -1,21 +1,73 @@
+psql:00-regress-install/share/contrib/postgis/legacy.sql:654: ERROR:  attempt to redefine parameter "postgis.backend"
+psql:00-regress-install/share/contrib/postgis/legacy.sql:678: ERROR:  attempt to redefine parameter "postgis.backend"
...

[strk]

Precedent discussion about the error is in #2382

[strk]

Does not happen with offline (script-based, rather than extension-based) tests.

[strk]

Got it, the "legacy.sql" script loads the "legacy.sql" enabled script from offline, which in turn loads the shared object from offline. There's then a clash of libraries between the online one and the offline one.

How should "legacy" be tested online ? @robe: how do you want people to enable "legacy" when using an extension ?

[strk]

Figured by myself, it was already handled in sfcgal-less run (we have support for loading scripts from install dir in run_test.pl!!).

See r13477 for the fix.