[fpc-devel] Building trunk of today fails on Windows: Error: Invalid DLL C:\WINDOWS\system32\common.dll, invalid header size

[Yuriy Sydorov]

On August 23, 2021 16:17:03 Bart via fpc-devel 
<fpc-devel at lists.freepascal.org> wrote:

> On Mon, Aug 23, 2021 at 2:57 PM Tomas Hajny via fpc-devel
> <fpc-devel at lists.freepascal.org> wrote:
>
>> The problem is that MS Windows employs a special trickery by which the
>> path to c:\windows\system32 (almost surely in your PATH) translates to
>> c:\windows\SysWOW64 _for_32-bit_binaries_ (only!). So in reality, that
>> directory _is_ in your PATH.
>
> Nice...
>
>> If the referenced
>> DLL is not found during compilation, the compiler tries to build the
>> import library "blindly", just based on assumptions formulated in the
>> source code.
>
> So:
> - 32-bit: it finds common.dll (thank you MS), which is the wrong one
> for the intended purpose (functions not found?) the compilation fails
> - 64-bit and arm-wince: it does not find common.dll (nor any of the
> other ones), but it can construct an importlibrary based on the
> sourcode and compilation succeeds (running a prgram that uses the unit
> will fail, since the libraries are just not on my system)
>
> Should I start the build process with a %PATH% that does NOT have
> C:\Windows\system32 in it?

Just move common.dll from SysWOW64 to system32. The file is placed wrongly 
by some installer.

Yuriy.