I'm using the relocatable-prog module, and assuming that my program may be running on a platform that needs to call `set_relocation_prefix`.
Therefore, I need to compute the `cur_prefix_arg`.
I assume that the program is installed with the standard directory layout under some prefix. To compute the current prefix, I use two values: argv[0], to give me the path to the executable, and the relative path from bindir to prefix. Then I compute (leaving out error checking):
// rel_prefix is `realpath --relative-to=@bindir@
@prefix@` char *rel_dir = mfile_name_concat(cur_bindir, rel_prefix, NULL);
char *can_prefix = canonicalize_filename_mode(rel_dir, CAN_MISSING);
(I use `CAN_MISSING` as I want to leave checks of the file system until later, but of course some other mode could be used.)
Because `realpath` is not available on all platforms, I have copied `relpath.[ch]` from GNU coreutils into my project, with some slight patching so that I don't need to import coreutils's system.h.
I have two questions:
1. Have I overlooked a simpler method of computing `cur_prefix_arg`? Whether or not there is a simpler way, it would be good to have this functionality included in the relocatable-prog gnulib module.
2. Even if I could have computed `cur_prefix_arg` more simply, `relpath` seems like quite useful functionality; would it be good to have as a gnulib module?
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