Hacker News Reader

Comment by jwatte | Hacker News Reader

Those who don't learn make are doomed to reimplement it. Poorly.

Also: never, ever, build a make system that relies on recursive make invocations.

Automake is a particularly egregious violator is this rule (and other sanity rules) and has probably hurt make more than anything else.

View on HN

Thankfully, you can now use automake without recursion if you set the "subdir-objects" option:

    AM_INIT_AUTOMAKE([subdir-objects])

and reference your source with their relative path in the (only) Makefile.am in $(top_srcdir)

    bin_PROGRAMS = foo

    foo_SOURCES = src/main.c                    \
                  src/foo.c      src/foo.h      \
                  src/quux/bar.c src/quux/bar.h \
                  src/quux/baz.c src/quux/baz.h

You can use relative paths like in most places automake accepts file names. The only time I've run into trouble using non-recursive automake (1.13.4) is adding flex+bison source. This requires BUILT_SOURCES, which is confusing, and automake is very picky and non-obvious about the names of the generated source files. I think it may not have been updated to support relative paths yet? It required some heavy workarounds:

    AM_YFLAGS = -d

    # this was VERY important
    # (must be abs_top_srcdir, not top_srcdir)
    foo_LFLAGS = --header-file=$(abs_top_srcdir)/src/xyzzy_lexer.h

    foo_SOURCES += src/xyzzy_lexer.l src/xyzzy_parser.y
    EXTRA_DIST  += src/xyzzy_lexer.h

    # note the inconsistency here
    BUILT_SOURCES += src/foo-xyzzy_lexer.c \
                     src/xyzzy_parser.h

    # ...and this doesn't match BUILT_SOURCES
    MAINTAINERCLEANFILES += src/foo-xyzzy_lexer.c \
                            src/xyzzy_lexer.h \
                            src/xyzzy_parser.h

Even with this annoyance, I would still highly recommend using this style instead of the traditional (recursive) automake. Autotools Mythbuster has more information on this other modern-autotools features:

https://autotools.io/automake/nonrecursive.html

Someone should implement make without the silly tabs.

And I thought I was the only one burned by this ;)

At least every 2nd C programmer working on a non-unix platform has been burned by this at least once. It's like a 10ft deep pothole on Broadway that won't get fixed because traditionalists see it as a 'national monument'.

"Why the tab in column 1? Yacc was new, Lex was brand new. I hadn't tried either, so I figured this would be a good excuse to learn. After getting myself snarled up with my first stab at Lex, I just did something simple with the pattern newline-tab. It worked, it stayed. And then a few weeks later I had a user population of about a dozen, most of them friends, and I didn't want to screw up my embedded base. The rest, sadly, is history."

-- Stuart Feldman

If you don't care about compatibility with existing Makefiles, you can do this already with GNU make; just set ".RECIPEPREFIX" to some other character.

Except for tup and ninja.

Reply on news.ycombinator.com