Re: Detect --disable-dependency-tracking in Makefile.am

[Zack Weinberg]

On Sat, Sep 30, 2023, at 1:07 AM, Jan Engelhardt wrote:
> On Saturday 2023-09-30 05:27, Dave Hart wrote:
>
>>I've added code to the ntp.org Makefile.am files to ensure the static
>>utility library libntp.a is up-to-date for each program that uses it, to
>>ensure the build is correct.  When building the project, this adds a bunch
>>of extra submake invocations which slows down the build.  I'd like to omit
>>those when --disable-dependency-tracking is used, to speed one-off builds
>>that are done by end-users and packagers.
>
> submake is pretty much independent of and from dependency tracking.
>
> The general direction contemporary projects take is to just not do submake
> anymore, because it's a slowdown whether or not deptracking is used.

To elaborate on that: it's been known since *1997* that recursive make is
always a bad idea. See <https://grosskurth.ca/bib/1997/miller.pdf> for gory
details.

It's too bad that Automake still, 26 years later, can only support non-recursive
builds in a fairly clunky way (manually adding subdirectory prefixes to every
single object file).  It shouldn't be *that* hard to make "subdirs = lib bin"
mush all the rules derived from {lib,bin}/Makefile.am into the top-level
generated Makefile.in, at least when there aren't any manually written rules
in the subdirectories.

zw