find_program without knowing specific directory structure

Code
1

I need to find an executable in an SDK where the structure can vary (including the names of intermediary folders). I just know that the executable will be under some root folder, but I don’t know at which level exactly. In a unix shell, I could just invoke:

cd <path_to_sdk>/root_folder/
find . -name "<program_name>"

The problem I am encountering is that find_program does not seem to work that way

  find_program(
      RE_2D_RENDER_EXECUTABLE RE2DRender
      PATHS "${ARG_RE_2D_RENDER_ROOT}"
      NO_DEFAULT_PATH
  )

will not find the program unless ARG_RE_2D_RENDER_ROOT is the exact folder in which RE2DRender is actually located. I know that I can provide multiple paths to find_program but my issue is that I just don’t know the names of those paths, I only know the top one

Or in other words, it doesn’t seem to check in all folder recursively down.

Is there another flavor of find_program that would behave like unix find?

2

I solve this kind of issue in my “FindOctave.cmake”, where GNU Octave install folder has the version number in it. I use find(GLOB) then find_program() https://github.com/scivision/octave-cmake-mex/blob/main/cmake/FindOctave.cmake#L66

3

Correct, find_program() doesn’t search recursively. That could be arbitrarily expensive. Instead, it searches well-defined sets of locations, suffixes and subdirectories, as described in the find_program() docs. If you need to recurse to arbitrary directory levels, you would have to implement that yourself with your own logic.

4

This is typically handled by something like (I’m making up versions since I don’t interact with Octave):

set(FindOctave_VERSIONS
  ${Octave_EXTRA_VERSIONS} # forward compat that users can use
  11.0 10.0 9.1 9.0)
set(paths)
foreach (version IN LISTS FindOctave_VERSIONS)
  list(APPEND paths foo-${version} foo/${version})
endforeach ()
# use ${paths} in `find_*` calls.

There should really just be some finite set of possible subpaths to search; in that case PATH_SUFFIXES is probably the way to go here.

5

yes I agree, instead of file(GLOB) which may not have a stopping condition, a finite list should be searched.

In my FindOctave.cmake, because I don’t use it that much and didn’t want to have to maintain it frequently, I did leave a single file(GLOB) just for Windows, though it could have no stopping condition, I feel that would be a rare case for a script I don’t want to maintain that much.

6

I wasn’t suggesting changing the default behavior of find_program. That being said adding a RECURSE option to find_program, that would then search recursively, would help in not having to reimplement the wheel every time this feature is required.

For the record, I ended up implementing it (note that I am not passing all find_param args because I don’t use them, so this implementation is somewhat simplified). It is not easy code to write, so that is why I think it would benefit CMake to have it built-in (optional of course…)

Note that since find_program sets a CACHE variable, then it is only “expensive” the first time it runs…

7

IIRC, it’s only expensive after the first time it succeeds.