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CompilerLauncher ​

Setting a compiler launcher to work correctly across different types of launchers or for different systems becomes difficult without a deeper understanding of various tooling for languages.

This module is provided specifically to reduce the overhead required to set a compiler launcher by initializing the default variable, or by setting a launcher on a per-target basis.

IXM also provides several find_package(MODULE) files for finding two very well known compiler launchers, ccache and sccache.

Commands ​

target_compiler_launcher ​

This command sets various properties for a given target for any language names passed to the PRIVATE, PUBLIC, or INTERFACE arguments. This property setting works with:

  • Makefile Generators
  • Xcode Generator

It will set -fno-pch-timestamp on the target if the user is using clang as the given language's compiler and the command can detect that sccache or ccache is being used as the launcher.

Additionally, if sccache or ccache are detected as the launcher, the MSVC_DEBUG_INFORMATION_FORMAT property will be set to Embedded automatically.

NOTE

Typically, developers will utilize a compiler launcher for caching of object files. However, this is not always the case, and this command is safe to use in those instances where a custom launcher is being provided.

Required Parameters ​

target
Name of the target to modify

Keyword Parameters ​

PUBLIC, PRIVATE, INTERFACE
Visibility for the language names given to the command. This affects the INTERFACE_<LANG>_COMPILER_LAUNCHER and <LANG>_COMPILER_LAUNCHER properties for the target.
LAUNCHER
Name of a target, a path to an executable file, or the name of an executable that can be found via find_program (not ixm::find::program).
If the name of a target is given, it does not have to exist at the time of the call. As long as it exists at the generation step, it will be used. The target can be either an IMPORTED target, or a target from the current project.
If the name of an IMPORTED target is given, its IMPORTED_LOCATION property will be read. If this property is empty, no launcher will be set.
If the name or path of an executable is given, it will be stored in a ${LAUNCHER}_EXECUTABLE cache variable.

WARNING

The ${LAUNCHER}_EXECUTABLE cache variable can sometimes be set if the name of a target is given and it already exists on disk. In these instances, the target will still be prioritized over the variable.

WARNING

If the ${LAUNCHER}_EXECUTABLE is not found and no valid target name is given, the compiler launcher property will be empty, however other properties such as the MSVC_DEBUG_INFORMATION_FORMAT property will still be set. This is due to limitations in CMake's generator expressions that prevent the ability to error with a useful message at generation time.

IMPORTANT

If using a target from the current build tree, users will have to call add_dependencies themselves manually to ensure the launcher is built before the current target.

Example ​

cmake
find_package(ccache 4.10)
# If `ccache::ccache` does not exist, the `${PROJECT_NAME}` target
# will *not* be set to run.
target_compiler_launcher(${PROJECT_NAME}
  LAUNCHER ccache::ccache
  PUBLIC
    CXX C
  PRIVATE
    OBJC)

© Izzy Muerte