Instructions to compile when GSL is installed in custom location

[drvdputt]

Instructions to compile when GSL is installed in custom location

[drvdputt]

I found the right option: -DGSL_ROOT_DIR=/path/to/prefix/. Documenting below how I came to that conclusion.

In my CMakeLists.txt, I have find_package(GSL REQUIRED). Setting -DCMAKE_FIND_DEBUG_MODE=TRUE prints out a message that the package has been found at /cmake_prefix/share/cmake-3.21/Modules/FindGSL.cmake. In other words, CMake ships with a file that contains instructions on how to find GSL.

In this module file, there are these lines:

# If the user has provided ``GSL_ROOT_DIR``, use it!  Choose items found 
# at this location over system locations.                                

So if I ever run into similar problems, I should use DCMAKE_FIND_DEBUG_MODE=TRUE to figure out what the module is actually doing. Reading the source code might reveal useful options.