Best you can do is to run make -n target to probe, but it's possible to write Makefiles that run code even though -n is used, which will defeat such probes at distribution scale. It quickly becomes an exercise in heuristics and output parsing.
"At distribution scale"... judging by your username, I take it your use case is something like finding out if a source tarball provides the standard targets like "install" and "distcheck", for all packages in debian? I can see how that would be rather painful.
I wonder if there's room for adding a "--dry-run-yes-really-dont-run-any-recipes-at-all" flag to make. As far as I remember the main use case for the current behaviour is (a) to run recipes that create makefiles that are then included into the main makefile, used in build systems that automatically figure out header dependencies and things like that; and (b) process makefiles in subdirectories for "recursive make" build systems. I wonder if you don't do those steps, would you actually miss out on any significant information re. top-level targets? I imagine that use case (a) is used to add prerequisites to existing targets, rather than creating new targets.
Or maybe a more general solution, instead of "--dry-run-yes-really", would be providing access to make's parser as a library, instead of having to parse the output of "make -p". I'm sure IDEs could make good use of that. Who's got time to implement that though.
You need to write a full parser to discover all the targets.
$ make -pqrf <(curl https://gist.githubusercontent.com/jgrahamc/2cc6df7fd5cd61c4d93f/raw/parallel) | grep '^[^ ]*:' | cut -d : -f 1
par-%
par-22
par-30
par-5
par-27
par-31
all
FORCE
/proc/self/fd/13
par-13
par-9
par-23
par-19
.SUFFIXES
par-15
par-7
parallel
par-29
par-28
.parallel
par-4
par-25
par-6
par-14
.DEFAULT
par-24
par-0
par
par-1
par-10
par-16
par-2
par-11
par-17
par-20
par-8
par-21
par-12
par-26
par-18
par-3I don't think grep '^[^ ]*:' really counts as writing a parser.
>
> Best you can do is to run make -n target to probe, but it's possible to write Makefiles that run code even though -n is used, which will defeat such probes at distribution scale. It quickly becomes an exercise in heuristics and output parsing.
The comment I replied to, chaosfactors, specifically specified grepping the makefile. You're arguing that you can find all the targets and I never said you can't. I simply said you can't find them all by only grepping the makefile.