Re: [PATCH] build: do not require help2man at build-from-tarball time

[Bernhard Voelker]

On September 10, 2012 at 1:41 PM Jim Meyering <address@hidden> 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 that feature, or when things are out of date, the regular commands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>

Have a nice day,
Berny