Ldc ImportC preprocessor failure (wrong option syntax) on Windows

[Richard (Rikki) Andrew Cattermole]

On 04/02/2025 10:50 PM, Bastiaan Veelo wrote:
> Hi,
> 
> On my personal machine everything works fine, but our CI build machine 
> suffers from this error:
> ```
> clang-cl.exe: warning: unknown argument ignored in clang-cl '- 
> target' (did you mean '--target='?) [-Wunknown-argument]
> clang-cl.exe: error: no such file or directory: 'x86_64-pc-windows-msvc'
> ```
> 
> I have the impression that options are given as the Microsoft 
> preprocessor expects them, but that the clang preprocessor is called 
> instead. I think that on my personal machine the Microsoft preprocessor 
> is called, which is also what I would expect, but I don't know of a way 
> to verify that; the workings of ImportC are rather opaque.

ldc and dmd have differing behaviors.

https://github.com/ldc-developers/ldc/blob/master/driver/cpreprocessor.cpp

And yes it prefers clang-cl.

Which means this is a bug.

> My hunch is that LDC doesn't detect the presence of the Microsoft 
> toolchain correctly. I do call `vcvarsall.bat x64` prior to invoking 
> ldc. Could there be a global configuration in effect on my personal 
> machine, but not on the CI build machine? One difference is that, 
> although we currently install compilers by unzipping archives and adding 
> to PATH, on my personal machine I have used the Windows Installer in the 
> past, which may have done additional things to configure my system.

Add to PATH, remove old.

That is all you need to do for installation after extraction.