[Scons-users] MSVC is broken for x86 builds on x64 hosts

[Daniel Moody]

Since VS 2015, there had been an 64 bit MSVC compiler available, along with
a 32 bit MSVC compiler:
https://docs.microsoft.com/en-us/cpp/ide/visual-cpp-tools-and-features-in-visual-studio-editions?view=vs-2017#compilers

You can cross compile using the 64 bit compiler to compile a 32 bit target,
taking advantage of larger addressable memory in the 64 bit compiler. If
you are on a 64 bit machine using VS >2015, scons defaults to using that
configuration. If you want to use a 32 bit compiler directly, you can also
set the environment var HOST_PLATFORM to 'x86' to force it.

In your case there may be an issue because you are using express edition
which doesn't have a 64 bit compiler, so scons didn't find the 64 bit to
32bit cross compiler, but neglected to check a possible valid configuration
using the 32 bit compiler directly, though that would conflict if you had
explicity specified HOST_PLATFORM as 64 bit and you didn't want a 32 bit
compiler as an option.


On Thu, Mar 28, 2019, 9:05 AM Michael Hartmann <michael.hartmann at qtronic.de>
wrote:

> The code to support Visual Studio tries to construct a path to cl.exe form
> the host arch (amd64) and the target arch (x86):
>
>
>
> vc.py:get_host_target()
>
> vc.py:get_host_target() req_target_platform:x86
>
> _check_cl_exists_in_vc_dir(): host platform amd64, target platform x86
>
> _check_cl_exists_in_vc_dir(): checking for cl.exe at C:\Program Files
> (x86)\Microsoft Visual
> Studio\2017\WDExpress\VC\Tools\MSVC\14.14.26428\bin\Hostx64\x86\cl.exe
>
> find_vc_pdir no compiler found 14.1
>
> trying to find VC 14.0
>
> find_vc_dir(): found VC in registry: C:\Program Files (x86)\Microsoft
> Visual Studio 14.0\VC\
>
> found VC 14.0
>
> vc.py:get_host_target()
>
> vc.py:get_host_target() req_target_platform:x86
>
> _check_cl_exists_in_vc_dir(): host platform amd64, target platform x86
>
> _check_cl_exists_in_vc_dir(): checking for cl.exe at C:\Program Files
> (x86)\Microsoft Visual Studio 14.0\VC\bin\amd64_x86\cl.exe
>
> find_vc_pdir no compiler found 14.0
>
> trying to find VC 14.0Exp
>
> find_vc_dir(): no VC registry key
> 'Microsoft\\VCExpress\\14.0\\Setup\\VC\\ProductDir'
>
> find_vc_pdir return None for ver 14.0Exp
>
>
>
> The problem is: Visual Studio is always a x86 application. The compiler
> for a x86 target is not a cross compiler and is found in VC\bin, not
> VC\bin\amd64_x86.
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