Hi All!

Untill yesterday, I had a lazarus app on Windows that worked fine with PostgreSQL. Now it keeps telling me it can't find libpq.dll. I have put libpq.dll in every directory that was recommend on many websites (e.g., in the app directory, in Windows\System32, Windows\SysWOW64, etc.) but I keep getting the error message when I try to start the app, and in the IDE when I try to connect the TPConnect component. I've rebooted every time I copy the dll just in case.

The pgAdmin III app works fine and sees all the tables and their contents so Postgres is working properly.

I even re-installed Lazarus (and put the dll in it's directory)

Any ideas?

Thanks in advance,

Don Ziesig

01.08.2014 1:31, Donald Ziesig ?????:

64-bit DLL versus 32-bit application or vice versa?

I will double check, but why would it change over night?

Donald Ziesig wrote

I will double check, but why would it change over night?

No idea but at least putting 32 bit libs in System32 or 64 bits in syswow64 as you said you have done is a big no-no. So it's a good idea to make sure you clean up incorrect bitness dlls...

2014-08-01 2:02 GMT+02:00 Reinier Olislagers :

This http://stackoverflow.com/questions/195590/locating-a-file-on-the-path should enable you to check if the dll can be accessed from your Lazarus app's working directory.

Donald Ziesig wrote

I will double check, but why would it change over night?

Windows Update?

Maxim Ganetsky wrote

64-bit DLL versus 32-bit application or vice versa?

(Why) does this not result in a more specific error message ? (How) can the calling program know about the "bittiness" of a dll / so it tries to load ?

-Michael

tries to load ?

One *could* differentiate it. Windows.LoadLibrary() returns ERROR_MOD_NOT_FOUND if the file does not exist and ERROR_BAD_EXE_FORMAT if the file is not a PE file or the architecture does not match.

Regards,
Sven
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(How) can the calling program know about the "bittiness" of a dll / so it tries to load ?

http://msdn.microsoft.com/en-us/library/windows/desktop/ms680313(v=vs.85).aspx

There is just field that tells what is architecture of file. This applies both to EXE and DLL.
You can see msdn has x86,x64 and itanium there, but there are many more existing.
In Linux situation is same, it also uses COFF and this field (AFAIK).

Nice !

But I suppose One *should* only differentiate if it can be done with other OSes, as well.

.
-Michael

Hi Again!

Thanks for all of the excellent suggestions.

After further investigation, it appears that the error message//is***misleading*. Lazarus *IS* finding libpq.dll, but it is not able to load it because *OTHER *system-level dll's that libpq depends on are missing. As mentioned before, it is possible that Windows Update caused the problem, but I haven't been able to confirm that yet.

I'll post the solution here when I find it.

After I get rid of all of the extraneous versions of libpq that I have scattered around my system ;-) .

Don Ziesig

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"payl" wrote

> > (How) can the calling program know about the "bittiness" of a dll / so

it tries to load ?

http://msdn.microsoft.com/en-us/library/windows/desktop/ms680313(v=vs.85).aspx

There is just field that tells what is architecture of file. This applies

both to EXE and DLL.

You can see msdn has x86,x64 and itanium there, but there are many more

existing.

In Linux situation is same, it also uses COFF and this field (AFAIK).

Linux uses ELF, not PE/COFF.

Regards,
Sven
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misleading. Lazarus IS finding libpq.dll, but it is not able to load it because OTHER system-level dll's that libpq depends on are missing. As mentioned before, it is possible that Windows Update caused the problem, but I haven't been able to confirm that yet.

Download Dependency Walker. It's normally distributed with Windows SDKs, but also available separately. With it you can check which libraries are missing (and even if some imports can't be resolved).

Regards,
Sven
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Linux uses ELF, not PE/COFF.

You are correct, I mistaken COFF from Unix with ELF. In ELF there is simply e_ident[EI_CLASS] at offset 4 and e_machine at offset $12. Source: http://en.wikipedia.org/wiki/Executable_and_Linkable_Format