[CMake] Changing /W3 to /W4 does not update CMakeCache.txt

[Craig Scott]

Your CMakeLists.txt file is modifying the *non-cache* variable
CMAKE_CXX_FLAGS. During CMake processing, a non-cache variable will
override a cache variable of the same name, but modifying a non-cache
variable won't update the cache. CMake is working as designed with regard
to the handling of CMAKE_CXX_FLAGS here, your expectation of the cache
being updated to reflect your changes to the non-cache variable is the
source of the confusion. Please review the following link which describes
this in more detail:

https://cmake.org/cmake/help/latest/manual/cmake-language.7.html#variables


On Fri, Feb 3, 2017 at 10:01 AM, Andrew Maclean <andrew.amaclean at gmail.com>
wrote:

> Consider the attached CMakeLists.txt script.
>
> When run, CMAKE_CXX_FLAGS is updated correctly, however the line:
> CMAKE_CXX_FLAGS:STRING=/DWIN32 /D_WINDOWS /W3 /GR /EHsc
> in CMakeCache.txt is never updated.
>
> However the build instructions e.g build.ninja reflect the correct command:
>  FLAGS = /DWIN32 /D_WINDOWS /W4 /GR /EHsc /D_DEBUG /MDd /Zi /Ob0 /Od /RTC1
> Similarly for the Visual Studio Build.
>
> I see this behaviour in my own code and also in VTK.
>
> Is there a reason why CMakeCache.txt does not get the update?
>
> Andrew
>
>
> --
> ___________________________________________
> Andrew J. P. Maclean
>
> ___________________________________________
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-- 
Craig Scott
Melbourne, Australia
https://crascit.com
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