MantisBT - CMake

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0015622

CMake

CCMake

public

2015-06-17 22:39

2016-06-10 14:31

Reporter

Paul "TBBle" Hampson

Assigned To

Kitware Robot

Priority

normal

Severity

feature

Reproducibility

N/A

Status

closed

Resolution

moved

Platform

OS Version

Product Version

Target Version

Fixed in Version

Summary

0015622: Add support for 64-bit Visual Studio Toolchains

Description

Visual Studio 2013 onwards have added a property to MSBuild "PreferredToolArchitecture" which can be set to "x64" to use the 64-bit compiler toolchain. This toolchain can produce all the same output targets: Win32, x64 and ARM; as the default (32-bit) compiler toolchain can.

It'd be great if this was supported somehow in CMake. Now that we have the -A flag for output architecture from the Visual Studio generators, this might be a duplicated set of generators, which only support -A for output architecture support. If there is an appropriate CMAKE property, that'd work too.

Ideally, we could flag off CMAKE_SYSTEM_PROCESSOR and CMAKE_HOST_SYSTEM_PROCESSOR to control this sort of cross-compiler behaviour, except that would:
(a) introduce a behaviour change for existing projects (hence perhaps a Visual Studio generator-specific policy); and
(b) require "fixing" CMAKE_SYSTEM_PROCESSOR, see issue 0015170

"PreferredToolArchitecture" is safe to set to "x64" on 32-bit platforms, as the VS2013 MSBuild scripts detect when the build is run on a 32-bit host or without the 64-bit toolset installed, and (silently) fall back to the 32-bit toolset.

As a workaround, "PreferredToolArchitecture" can be set as an environment variable, in case anyone finds this feature request and doesn't want to wait for implementation.

Steps To Reproduce

Additional Information

MSBuild documentation at https://msdn.microsoft.com/en-us/library/dd293607(v=vs.120).aspx [^] shows this flag for VS2013 and VS2015 RC.

In VS2010 and VS2012, you could set the property "_IsNativeEnvironment" to "true" to use the 64-bit toolchain. This was not formally documented on MSDN, but in various blog posts. Anecdotally, it didn't support cross-compiling 32-bit or ARM targets from the 64-bit toolchain.

The "_IsNativeEnvironment" property is actually an internal property for the MSBuild C++ targets, but you must set it manually in pre-VS2013 because the IDE is always 32-bit and always provides the PROCESSOR_ARCHITECTURE environment variable as "x86". The actual intent of the toolchain code was to detect and enable _IsNativeEnvironment when running from a 64-bit environment, as seen in this snippet:

<_IsNativeEnvironment Condition="'$(PROCESSOR_ARCHITECTURE)' == 'AMD64' and '$(Platform)' == 'X64'">true</_IsNativeEnvironment>
<_IsNativeEnvironment Condition="'$(PROCESSOR_ARCHITECTURE)' == 'IA64' and '$(Platform)' == 'Itanium'">true</_IsNativeEnvironment>

See https://social.msdn.microsoft.com/Forums/en-US/d6b352ea-12b6-4867-b86d-a052fbab1da4/how-can-switch-to-native-x64-compiler-to-compile-x64-program [^] for discussion.

This logic is still present in VS2013, but the "PreferredToolArchitecture" presents the user-selectable interface. VS2013 attempts to honour the "_IsNativeEnvironment" property and set "PreferredToolArchitecture" to match, but apparently that doesn't work, see https://connect.microsoft.com/VisualStudio/feedback/details/800059/isnativeenvironment-true-no-longer-works-on-visual-studio-2013-rc [^]

A request for this appeared on Stack Overflow at http://stackoverflow.com/questions/23186620/use-native-64bit-toolset-in-visual-studio-2013 [^] and a CMake mailing list request for a workaround at http://www.cmake.org/pipermail/cmake/2014-February/057045.html [^]