[IBPP-DISCUSS] Problem with IBPP and Firebird libfbembeded

[Tony W. <ton...@mw...>]

Olivier,

I have come across a problem with using IBPP and the Firebird embedded
server (libfbembed.so) under Linux which could be worked around with
Firebird 2.1 but not with Firebird 2.5.

The problem is with use of the security database.

In Firebird 2.1, the FIREBIRD environment variable was fully respected.
However, in Firebird 2.5, it is ignored for the security database.
Personally, I regard this as a defect in Firebird 2.5. However, when
using libfbembed.so rather than libfbclient.so, there is a workaround
(arguably the proper approach) which breaks IBPP.

You can explore the problem with "isql" under classic builds. This is
linked to libfbembed.so and exhibits the following behaviour when
opening a local database (i.e. no host name specified).

1. When called with a -user argument or with the ISC_USER environment
variable set, it tries to open the security database even though it will
not try to verify the user. If the current user is not a member of the
"firebird" group, this will fail.

2. When called without a -user argument and without the ISC_USER
environment variable set, it does not access the security database and
opens the selected database using only unix permissions to control
access. This works regardless of whether the current user is a member of
the firebird group.

However, when trying the same with IBPP, the DB->Connect() call verifies
that the username is non-empty and returns a logic error if no username
is specified. It is thus impossible to use IBPP with the Firebird 2.5
embedded server unless the user is a member of the firebird group (which
may not be desirable or possible).

Only a minor change is required to remove this (helpful?) check and a
patch is attached, which appears to work on my system.

The patch also includes some other changes introduced to make use of the
embedded server easier (i.e. instead of softlinking it to fbclient.so).
This replaces your "TODO" with unix dynamic library loading, choosing
the library from an ordered list of library names added to the top of
_ibpp.cpp. This list tries "libfbembed.so.2.5", "libfbembed.so.2.1" and
"libfbclient.so.2" in that order. It can also be overridden by
specifying the environment variable FBLIB which is then assumed to be
the Firebird Client Library Name.

Regards

Tony Whyman
MWA