Reinier Olislagers wrote:
On 29/09/2014 19:30, Reinier Olislagers wrote:
Re bug report: agreed. I'll raise it.

Jonas has already closed it, noting

"http://msdn.microsoft.com/en-us/library/windows/desktop/ms682583%28v=vs.85%29.aspx

"***
The entry-point function should perform only simple initialization or termination tasks. It must not call the LoadLibrary or LoadLibraryEx function (or a function that calls these functions), because this may create dependency loops in the DLL load order. This can result in a DLL being used before the system has executed its initialization code.
***

"I.e., what you are doing is unsupported ("must not call the LoadLibrary or LoadLibraryEx function"). I think that on most unix platforms, trying to load libraries from other the init function of other libraries is not supported either."

However I'd precede that by a thought based on what Jose said. In your example, you're opening the database in the initialisation block of businesslayer.pas, which is invoked at an arbitrary position in the init sequence of the DLL/so. If that operation were moved instead to the initialisation block of testdbdll.lpr, which in the context of the DLL/so is analogous to a program's main block, it might work.

If having the open operation in testdbdll.lpr works but having it in businesslayer.pas doesn't, then it's fair to ask why in the context of FPC (hence my suggestion of a bug report). If neither works, then it's presumably explained by Jonas's note i.e. it's a "feature" in the context of the library loader.

In practice, I still think it's best for the main program to tell the database when and how to initialise, since there's things that it might know about the user's intentions or environment that aren't known by the dynamically-loaded libraries (crude example: you might want to know the compile-time name of the project of which the main program was a part).

--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]
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