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sccache ​

IXM provides an sccache package that allows user to use sccache as an IMPORTED executable target. This can then be used to set the CMAKE_<LANG>_COMPILER_LAUNCHER variable or a target's specific <LANG>_COMPILER_LAUNCHER.

Targets ​

This module only provides one IMPORTED executable target. If the sccache executable cannot be found, this target is not available.

sccache::sccache
The sccache executable (or a sccache compatible executable)

Usage ​

To get the full usage out of sccache, a few extra operations must be performed.

  1. The MSVC_DEBUG_INFORMATION_FORMAT property MUST be set to Embedded, otherwise sccache will fail to cache and users will get inscrutable errors regarding PDB services.
  2. sccache does not support C++ Modules at this time. It also does not support Clang C++ modules.
  3. When using sccache and multiple values for CMAKE_OSX_ARCHITECTURES, users will need to set SCCACHE_CACHE_MULTIARCH to true. Additionally, users might need to also change to a so-called "direct mode" and rely on hashing of the command line arguments instead of the preprocessed source.

Example ​

One way to use sccache is to simply require users to have it exist on their system.

cmake
find_package(sccache REQUIRED)

set(CMAKE_CXX_COMPILER_LAUNCHER $<TARGET_PROPERTY:sccache::sccache,IMPORTED_LOCATION>)
set(CMAKE_C_COMPILER_LAUNCHER $<TARGET_PROPERTY:sccache::sccache,IMPORTED_LOCATION>)

set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT Embedded)

However, this approach is not flexible for use cases where it is not always possible to rely on sccache existing on a given system. Thus, it is better to use a more fallible approach.

cmake
find_package(sccache)

if (TARGET sccache::sccache)
  set(CMAKE_CXX_COMPILER_LAUNCHER $<TARGET_PROPERTY:sccache::sccache,IMPORTED_LOCATION>)
  set(CMAKE_C_COMPILER_LAUNCHER $<TARGET_PROPERTY:sccache::sccache,IMPORTED_LOCATION>)
endif()

set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT $<IF:$<TARGET_EXISTS:sccache::sccache>,Embedded,ProgramDatabase>)

Because so many of these values can be set with generator expressions, it allows users a great amount of flexibility to work around the instance where sccache could not be found.

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