[fpc-devel] Fix for an annoying error

[Michael Van Canneyt]

On Tue, 30 Nov 2021, J. Gareth Moreton via fpc-devel wrote:

> That was a conundrum I was trying to answer when making the patch.  What 
> is a warning and what is an error?
>
> A lot of the verification code is dependent on compile-time constants 
> whose values depend on the compiler's target platform, including header 
> sizes, so any mismatch is an error case, and the checking of header 
> sizes and the COFF magic number are done together, since the correct 
> header size is dependent on the magic number's value.
>
> I didn't look too much further beyond the verification code, but if it's 
> able to detect if a DLL is 32-bit on a 64-bit system and vice versa, I 
> feel that's a warning rather than error because, in my experience, it's 
> down to a default system configuration (I got the error on a 
> freshly-installed machine) rather than something untoward.  If the DLL 
> is missing, that should probably be a warning too and I'll see if I can 
> make that change.  A corrupted DLL is definitely an error though.
>
> I didn't do a verification to see if the DLL is for AArch64, for 
> example, since that situation is more unlikely.  It also starts to bloat 
> the compiler code.
>
> Either way, using a DLL for a different build of Windows is a warning at 
> the very least because the project will probably break when you try to 
> run it.

Personally, I think that reverting to a warning was a mistake.

You have no guarantee that the resulting program will run if you ignore the
"error":

Not on the system where you compiled, not on the system where you will run the program.

For your particular problem: I looked at the source code of the oracle unit.
As far as I can see there is no need to include the common.dll in the
linklib statements, all that should be linked is the oracle dll. 
It may be a better solution simply to remove that line.

Michael.