Bernhard Voelker wrote: > On September 10, 2012 at 1:41 PM Jim Meyering <j...@meyering.net> wrote: > >> I want each *existing* .1 file to depend solely on its corresponding .c file. >> However, when a .1 file does not exist, *then* I want it to depend on >> its corresponding executable. >> I.e., I do *not* want to rebuild an existing .1 file >> solely because we have a newer binary, when the .1 file >> is newer than its dependents (.c and .version). >> I started work on a prefix to the .x.1 rule in man/local.mk, >> but it relies on test's -nt operator. With a shell lacking >> that feature, or when things are out of date, the regular commands >> would run. Otherwise, it would simply touch the .1 file and exit >> successfully. >> >> AFAIK, there is no way in GNU make to specify dependencies that vary >> depending on the existence of a target. Does anyone know otherwise? >> I.e., a rule that would apply when foo.1 does not exist, vs. another >> one (with different dependents) that would apply when it does exist. > > Not sure, but maybe something for .SECONDARYEXPANSION ? > http://www.gnu.org/software/make/manual/html_node/Secondary-Expansion.html#Secondary-Expansion > <http://www.gnu.org/software/make/manual/html_node/Secondary-Expansion.html#Secondary-Expansion>
Thanks! That looks promising, i.e,. to make the second expansion depend on the existence of $@. If it works as I'm imagining, it would be cleaner than having to create an if-else block per target. Filing that away for the day we can rely on GNU make.
