• Vladimirs Nordholm (14/14) Aug 20 2019 Hello.
• Dennis (17/19) Aug 20 2019 Importing only specifies that you expect the symbols to be there,
• Vladimirs Nordholm (4/10) Aug 20 2019 Thank you for the explanation Dennis.

Vladimirs Nordholm <v vladde.net> writes:

Hello.

I recently reinstalled Windows 10 (build 1903), and downloaded 
DMD (v2.087.1) and dub (v1.16.0).

My project no longer compiles, giving the following errors:

     error LNK2019: unresolved external symbol GetSystemMetrics 
referenced in [...]
     error LNK2019: unresolved external symbol SetWindowPos 
referenced in function [...]

The function `GetSystemMetrics` and `SetWindowPos` can be found 
at 
https://github.com/dlang/druntime/blob/master/src/core/sys/windows/winuser.d ,
line 3874 and 4095 respectively.

In code I have `import core.sys.windows.winuser;`, but still get 
this error.

Any clues to why this might happen?

Dennis <dkorpel gmail.com> writes:

On Tuesday, 20 August 2019 at 17:17:01 UTC, Vladimirs Nordholm 
wrote:
 In code I have `import core.sys.windows.winuser;`, but still 
 get this error.

Importing only specifies that you expect the symbols to be there, 
it doesn't mean the functions are linked in.

On Windows there are three targets, 32-bit OMF (old dmd default), 
32-bit MSCoff and 64-bit MSCoff (dub defaults to MSCoff since not 
too long ago). While DMD ships with import libraries for all 
targets, I never know which ones get linked in by default and 
which ones don't.

Usually when I get Windows linking errors I either switch the 
target (the OMF import libraries are sometimes lacking, so then I 
compile with --arch=x86_mscoff or --arch=x86_64) or explicitly 
link the import libraries.
Just quickly Google a function like GetSystemMetrics:
https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getsystemmetrics
On the bottom it says "Library: User32.lib" so I add `pragma(lib, 
"User32.lib");` to my module using it.

Vladimirs Nordholm <v vladde.net> writes:

On Tuesday, 20 August 2019 at 17:29:15 UTC, Dennis wrote:
 On Tuesday, 20 August 2019 at 17:17:01 UTC, Vladimirs Nordholm 
 wrote:
 [...]

 Importing only specifies that you expect the symbols to be 
 there, it doesn't mean the functions are linked in.

 [...]

Thank you for the explanation Dennis.

Never done the `pragma(lib, ...)` before, but that definitely 
solved the problem!