Everything else aside, there's a profound difference between MAKEFLAGS=-r and MAKEFLAGS+=-r. The latter is far less destabilizing. And yes, GNUMAKEFLAGS is definitely better for this use.
On Mon, Jul 17, 2023 at 5:45 AM Bruno Haible <br...@clisp.org> wrote: > Dmitry Goncharov wrote: > > Once the makefile author knows the makefile does not need built-in > > rules, they should add MAKEFLAGS=-r in the makefile and > > this will do a good service to all their users. > > The premise "does not need built-in rules" is likely true for most > Makefiles > generated by GNU Automake, because > - GNU Automake generates its own rules already, > - Whenever rules are executed that don't obey the variables listed in > [1], > such as CPPFLAGS, it is a bug that the package's user should rightfully > report. > > So I wondered whether I should add this variable definition in the > Makefile.am > files of my GNU packages. But then I read this in the documentation [2]: > > "you should be sure not to include any options that will drastically > affect the actions of make" > > and > > "It’s best to use GNUMAKEFLAGS only with flags which won’t materially > change the behavior of your makefiles." > > and this on stackoverflow [3]: > > "You shouldn't set MAKEFLAGS at all. ... > MAKEFLAGS is intended, really, to be an internal implementation passing > arguments from a parent make to a child make. It's not intended, > generally, to be modified by a makefile." > > and this in Oracle's documentation [4]: > > "Do not define MAKEFLAGS in your makefiles." > > And finally, MAKEFLAGS is not even mentioned in the main index of the GNU > Make > documentation [5], and only regarding "recursion" in the Variables index > [6]. > > > The manual should lead by example. > > Yes, I agree. But if the example contradicts all the advice given in the > rest > of the manual and elsewhere, I will certainly not use it in my Makefiles. > > Also, what the example did not tell me: If a Makefile uses MAKEFLAGS=-r and > the Makefile in a subdirectory needs built-in rules, will the MAKEFLAGS=-r > setting propagate to the subdirectory? In other words, is it a good idea > to use MAKEFLAGS=-r in Makefiles that recurse to other Makefiles (and that > are maintained independently)? > > Bruno > > [1] > https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.71/html_node/Preset-Output-Variables.html > [2] > https://www.gnu.org/software/make/manual/html_node/Options_002fRecursion.html > [3] https://stackoverflow.com/questions/19611004/ > [4] https://docs.oracle.com/cd/E19504-01/802-5880/make-65/index.html > [5] > https://www.gnu.org/software/make/manual/html_node/Concept-Index.html#Concept-Index_cp_letter-M > [6] > https://www.gnu.org/software/make/manual/html_node/Name-Index.html#Name-Index_fn_letter-M > > > > >
