To fix this, we must check all DB colums which we expect to be of BOOLEAN type, and if the actual type is different then the table structure must be updated.

This should be done in the installer as part of the upgrade process.

Systems newly installed with 1.1.0 or above are not affected by this.

This is where we originally patched adodb to handle this, but those changes were pulled.

We need to decide whether in 2.x we want to use boolean or small int for these fields.

The obvious fix for 1.2.15 is too revert adodb back to the release where we included functionality to handle this, until we release 2.x

The obvious fix for 1.2.15 is too revert adodb back to the release where we included functionality to handle this, until we release 2.x

1.2.15 has the fix in, it's only been pulled in master; the issue here is when upgrading from old releases of Mantis (pre 1.1.0) and the only fix is to apply some script on the DB to convert the columns, patching the code will do nothing (unless you mean reverting ADOdb type for L columns back to smallint, which IMO is not an option).

smallint is the correct data type for adodb to be using:

L: Integer field suitable for storing booleans (0 or 1)

The use of "boolean" is really a mistake given that definition. Smallint is the easy solution - however, I think we might actually want 'bit' in postgresql as the correct field type in this scenario.

smallint is the correct data type for adodb to be using:
L: Integer field suitable for storing booleans (0 or 1)

Possibly, but the fact is that ADOdb has been using BOOLEAN since 4.96. I'm sure you'll agree that it's not worth the effort to go and argue the case with John Lim to change back to SMALLINT or anything else...