Fixed build errors resulting from upgrading to VS2019 compilers

[harishsk]

Fixes #3893

The default CMAKE_C_FLAG for debug configuration sets /ZI to generate a PDB capable of edit and continue. In the new compilers, this is incompatible with /guard:cf which we set for security reasons. So to fix, we need to go back to a regular pdb generated by the /Zi flag.

Since this part of the default CMake rules, we need to override the full default set and update only that particular flag.

[wschin]

Where do those flags /MDd /Zi /Ob0 /Od /RTC1 /JMC come from? Are they default flags in CMake? Could you please add more details for maintaining them in the future?

[harishsk]

Yes, those are the default flags in CMake. I will add a bit more detail and submit another PR soon.

[codemzs]

thanks, @harishsk

[harishsk]

Purely for educational purposes...these are the recent changes in Windows-MSVC.cmake that caused this issue:

# default value for Just My Code flag
set(_JMC "")
# default value for Debug Information Format flag
set(_DEBUGINFOFORMAT_DEBUG "/Zi")


if("x${CMAKE_C_COMPILER_ID}" STREQUAL "xMSVC" OR "x${CMAKE_CXX_COMPILER_ID}" STREQUAL "xMSVC" )
    # JMC only supported in MSVC
    if(MSVC_VERSION GREATER_EQUAL 1915)
      set(_JMC "/JMC")
    endif()
    # /ZI is supported by MSVC only, not by clang-cl for example.
    set(_DEBUGINFOFORMAT_DEBUG "/ZI")
  endif()

string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " /MDd ${_DEBUGINFOFORMAT_DEBUG} /Ob0 /Od ${_RTC1} ${_JMC}")

[janvorli]

@harishsk where have you found the stuff above? I've looked at the Windows-MSVC.cmake in all versions from 3.14 till 3.15 and none of this was there (looking via https://github.com/Kitware/CMake). And cmake 3.14.2 with VS2019 builds fine without your change (And the vcxproj files contain /Zi, not /ZI).

[eerhardt]

I am experiencing the same as @janvorli. I can build successfully on VS 2019 with CMake 3.14.5 without this change.

I sort of think this change should be reverted until we know more. I don't like the fact that we are clobbering the defaults.

[harishsk]

Where is your CMake located? And what is the version reported for CMake.exe --version

Mine is here: "C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\cmake.exe"

And it reports: cmake version 3.14.19050301-MSVC_2

The changes I reported above are in this file:
c:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\share\cmake-3.14\Modules\Platform\Windows-MSVC.cmake

[eerhardt]

My CMake is located at C:\Program Files\CMake and I installed 3.14.5 from https://cmake.org/download/ and added it to my $PATH. This is all documented on https://github.com/dotnet/machinelearning/blob/master/docs/building/windows-instructions.md#required-software.

@janvorli informed me there might be an issue with the CMake shipped by VS 2019:

Comparing the Windows-MSVC.cmake of vanilla 3.14.2 and the 3.14 in VS2019, I can see that they removed this at one place:

# default value for Just My Code flag
set(_JMC "")
# default value for Debug Information Format flag
set(_DEBUGINFOFORMAT_DEBUG "/Zi")

And added this at another

  if("x${CMAKE_C_COMPILER_ID}" STREQUAL "xMSVC" OR "x${CMAKE_CXX_COMPILER_ID}" STREQUAL "xMSVC" )
    # JMC only supported in MSVC
    if(MSVC_VERSION GREATER_EQUAL 1915)
      set(_JMC "/JMC")
    endif()
    # /ZI is supported by MSVC only, not by clang-cl for example.
    set(_DEBUGINFOFORMAT_DEBUG "/ZI")
  endif()

It seems as if they just made a mistake in the "i" case

@jkotas - do you happen to know anyone on the Visual Studio team who works on the CMake they ship? I'd like to find out if this is a bug in VS 2019.

[janvorli]

Btw, it seems that a cleaner way to fix the problem would be to use string(REPLACE ....) cmake command to just replace /ZI by /Zi in CMAKE_C_FLAGS_DEBUG instead of overwriting all the options with what we assume should be there. Like this:

string(REPLACE "/ZI" "/Zi" CMAKE_C_FLAGS_DEBUG  ${CMAKE_C_FLAGS_DEBUG})

[harishsk]

Yes, I have CMake installed in Program Files on my laptop and I don't see this bug. On my desktop, I don't have CMake installed and the one shipped in Visual Studio gets used, resulting in this bug.

This is a bug in VS2019. And as my comment in the fix states, we can remove those lines after the defaults are fixed.

I agree what you propose is a cleaner fix. I have tested it and submitted a new pull request.

@janvorli and @eerhardt Can you please review and approve?

[jkotas]

do you happen to know anyone on the Visual Studio team who works on the CMake they ship?

Take a look at https://github.com/microsoft/CMake . I believe it has the sources for the version that VS ships; and you can also find the people who work on it there.