Re: Conditional broken line in recipe

[Alejandro Colomar]

Hi Paul,

On 2023-09-03 04:09, Paul Smith wrote:
> On Sun, 2023-09-03 at 01:03 +0200, Alejandro Colomar wrote:
>> I was also wondering... is ONESHELL significant for performance? 
>> Does the reduction in number of shells speed up things?
> 
> It might increase performance but that's not what it's for primarily,

For those wondering, here's an experiment with a rule that runs a few
shells (given appropriate values for certain variables):


$ time make -j install DESTDIR=/tmp/foo Z=.gz LINK_PAGES=symlink >/dev/null

real    0m6.229s
user    0m17.820s
sys     0m5.269s
$ sed -i '/ONESHELL/s/^/#/' GNUmakefile 
$ time make -j install DESTDIR=/tmp/bar Z=.gz LINK_PAGES=symlink >/dev/null

real    0m8.511s
user    0m23.823s
sys     0m7.511s


It's not orders of magnitude, but it might be interesting to cut a
25%, considering no obvious pitfalls (when you overcome the SHELL
errors, that is :D).  For rules with just 1 canned recipe, the times
didn't change.

Here's the rule I used (I chose it because it's the most complex rule
in the Makefile, as it has 3 canned recipes):


$(_manpages):
        $(info INSTALL  $@)
        <$< \
        $(SED) $(foreach s, $(MANSECTIONS), \
                -e '/^\.so /s, man$(s)/\(.*\)\.$(s)$$, $(notdir 
$(man$(s)dir))/\1$(man$(s)ext)$(Z),') \
        | $(INSTALL_DATA) -T /dev/stdin $@
ifeq ($(LINK_PAGES),symlink)
        if $(GREP) '^\.so ' <$@ >/dev/null; then \
                $(GREP) '^\.so ' <$@ \
                | $(SED) 's,^\.so \(.*\),../\1,' \
                | $(XARGS) -I tgt $(LN) -fsT tgt $@; \
        fi
endif
ifeq ($(Z),.bz2)
        if ! $(TEST) -L $@; then \
                $(BZIP2) $(BZIP2FLAGS) <$@ \
                | $(SPONGE) $@; \
        fi
else ifeq ($(Z),.gz)
        if ! $(TEST) -L $@; then \
                $(GZIP) $(GZIPFLAGS) <$@ \
                | $(SPONGE) $@; \
        fi
else ifeq ($(Z),.lz)
        if ! $(TEST) -L $@; then \
                $(LZIP) $(LZIPFLAGS) <$@ \
                | $(SPONGE) $@; \
        fi
else ifeq ($(Z),.xz)
        if ! $(TEST) -L $@; then \
                $(XZ) $(XZFLAGS) <$@ \
                | $(SPONGE) $@; \
        fi
endif



> at least not in my opinion.  It's there for people who want to use
> shells other than POSIX sh as their SHELL value,

Well, my SHELL is not the POSIX sh, as I'm using bash(1), but I get
it's still POSIX-sh-like, not python.  :)

> where it's not so easy
> to create an entire script on a single line and using backslashes.

Can we really call it script if it's invoked via sh -c?  It's more
like a command line.  :)

Jokes apart, can you put an example of such a scenario?  I'm not
imagining it.


BTW, apart from fixing the SHELL (which was a good thing, anyway),
the only change I needed was to remove the '+' from a couple of
recipes (and keep only the first one).  Not a big deal.  Most rules
work without modification.


Cheers,

Alex

-- 
<http://www.alejandro-colomar.es/>
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