MSVC Precompiled header flags not supported: "multiple input files"; Seeking workaround...

[DragonAxe]

Versions tried: v0.2.15 and v0.2.16-alpha.0 (master build at 3f318a8675e4c3de4f5e8ab2d086189f2ae5f5cf)

Per a comment here: https://github.com/mozilla/sccache/issues/950 I tried downgrading to v0.2.12. However, while I no longer got "multiple input files" warnings, all compile requests were categorized as "Non-cacheable compilations".

Here is an example compile command:

C:\path\to\sccache.exe C:\PROGRA~2\MICROS~1\2019\BUILDT~1\VC\Tools\MSVC\1428~1.299\bin\Hostx64\x64\cl.exe 
 /nologo
 /TP
 -DBOOST_ALL_DYN_LINK
 -DBOOST_ALL_NO_LIB
 -DBOOST_DATE_TIME_POSIX_TIME_STD_CONFIG
 -DBOOST_EXCEPTION_MINI_BOOST
 -DBOOST_FILESYSTEM_NO_DEPRECATED
 -DBOOST_STACKTRACE_LINK
 -DBOOST_TEST_IGNORE_NON_ZERO_CHILD_CODE
 -DBOOST_TEST_IGNORE_SIGCHLD
 -DBOOST_THREAD_VERSION=3
 -DBOOST_USE_WINDOWS_H
 -DBOOST_USE_WINFIB
 -DBOOST_UUID_RANDOM_PROVIDER_FORCE_WINCRYPT
 -DPROJECT_FLAG_SHARED_LIBRARY
 -DNOMINMAX
 -DPROTOBUF_USE_DLLS
 -DTEST
 -DWIN32_LEAN_AND_MEAN
 -IC:\src\path\to\includes
 -I.
 -IC:\src\path\to\includes\project1\src
 -IC:\src\path\to\includes\project2\include
 /DWIN32
 /D_WINDOWS
 /GR
 /EHsc
 /D_WIN32_WINNT=0x0601
 /DWINVER=0x0601
 /Zc:__cplusplus
 /FS
 /errorReport:none
 /Zm500
 /bigobj
 /MP
 /MD 
 /Ob2
 /DNDEBUG
 /GS-
 /O1
 /Oi
 /Zi
 -experimental:external
 -external:W0
 -external:IC:/path/to/external/includes/project1/includes
 -external:IC:/path/to/external/includes/project2/includes
 -external:IC:/path/to/external/includes/project3/includes
 -external:IC:/path/to/external/includes/project4/includes
 -external:IC:/path/to/external/includes/project5/includes
 -external:IC:/path/to/external/includes/project6/includes
 -external:IC:/path/to/external/includes/project7/includes
 -external:IC:/path/to/external/includes/project8/includes
 /D_USE_MATH_DEFINES
 /DNOMINMAX
 /DWIN32_LEAN_AND_MEAN
 /permissive-
 /Zc:externConstexpr
 /await
 /W4
 /D_SILENCE_CXX17_ALLOCATOR_VOID_DEPRECATION_WARNING
 /D_SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING
 /D_CRT_SECURE_NO_DEPRECATE
 /wd4251
 /wd4275
 /wd4503
 /wd4127
 /wd4100
 /wd4702
 /wd4267
 /WX
 -std:c++latest
 /showIncludes
 /Fopath\to\object\output\dir\objectfile.cpp.obj
 /Fdpath\to\program\database\dir\
 /FS
 -c C:\path\to\source\cpp\file\code.cpp

Thank you all in advance!

[DragonAxe]

After some more testing, it appears the /Zm500 argument is not recognized as a valid flag.

[jviotti]

@DragonAxe Do you mean that removing /Zm500 made it work for you?

[DragonAxe]

@jviotti I didn't try removing that flag. Instead, I added some print statements to parse_arguments() in src/compiler/msvc.rs to see which of my compiler options was being picked up as an input file by Sccache. In that same file I also noticed this comment: // TODO: what do do with precompiled header flags? eg: /Y-, /Yc, /YI, /Yu, /Zf, /ZH, /Zm

I tried adding msvc_flag!("Zm500", PassThrough), to the list of recognized msvc_args!, but wasn't able to get it to work by ignoring that argument (just as a temporary workaround to get things to work locally). I don't know enough about Rust or Sccache to do things other than trial and error at this point.

[DragonAxe]

@DragonAxe Do you mean that removing /Zm500 made it work for you?

@jviotti Yes, after disabling the addition of the /Zm500 flag in my cmake, I was able to get sccache to start caching (and the speed increase was glorious! :D ).