CMake debug find

February 10, 2022

CMake --debug-find option gives extensive human-readable trace output for where the CMake find_ operations are looking for files. In most CMake projects, there are many find_ operations, and so the cmake --debug-find output can be overwhelming to scroll through. The example commands refer to this CMake script:

# arbitrary other packages not of interest to trace finding
find_package(Git)

# package that's not working right, to debug
find_package(LAPACK)

# arbitrary find_* to trace variable
find_library(MYLIB NAMES mylib)

Package-specific debug-find is available:

cmake --debug-find-pkg=LAPACK

Variable-specific debug-find is available:

cmake --debug-find-var=MYLIB

It’s also possible to target specific find_* calls via CMAKE_FIND_DEBUG_MODE. To debug only the finding of LAPACK:

# arbitrary other packages that are not of interest to trace finding
find_package(Git)

# package that's not working right, to debug
set(CMAKE_FIND_DEBUG_MODE on)
find_package(LAPACK)
set(CMAKE_FIND_DEBUG_MODE off)