Re: [bug #61594] suggest new $(hash ...) function

[Tim Murphy]

I have added such a function as a loadable library before - you might consider that if you can't get it done another way.

https://github.com/tnmurphy/extramake

look at hash.c.  To try it :

cd example && make -f example.mk

I called the function siphash24 because that's what I used - and its' definitely not cryptographic.  I had similar needs such as generating unique target names from many inputs where I didn't want the target name to be of unlimited length or to have illegal characters.

$(shell) was useless as it is far too slow.

I would suggest having $(hash) and $(<hash-alg>)  - because then people who care about the algorithm will be able to choose it.


FYI loadable modules are quite cool:

SOURCES:=proga.c progb.c
OBJECTS:=$(SOURCES:.c=.o)


include ../xtra.mk
XTRA_OUTPUTDIR:=.
XTRA_SOURCE:=..
-load $(XTRA_OUTPUTDIR)/hash$(XTRA_EXT)

LIBVERSION:=$(siphash24 $(SOURCES))
LIBNAME:=prog_$(LIBVERSION).so

$(LIBNAME): $(OBJECTS)
        cc -o $@ $^ -shared

$(OBJECTS) : %.o : %.c
        cc -c -o $@ -fPIC $^

include ../hash.mk

The above will build the $(siphash24) function (if it's not there already) and then use it. 

On Wed, 1 Dec 2021 at 12:37, Edward Welbourne <edward.welbourne@qt.io> wrote:

rsbecker@nexbridge.com  (1 December 2021 13:08) wrote:
> I would suggest that adding cryptography to GNU Make would limit its
> reach. There are jurisdictions where it is questionable to import
> software containing any cryptography. In addition, there are numerous
> tools for doing what you want. Something along the lines, for example,
> of:
>
> $(shell git hash-object obj)
>
> Is a simple function that is already supported by GNU Make without
> having to introduce cryptography. This would make a lot more sense to
> me to keep hashing out of GNU Make.

+1.  It also leaves it to the make file author to decide which hash
function to use.  If make took charge of that decision, it would be
stuck with the hash selected for all time, since it would have no way of
knowing how the resulting hashes have been used by diverse different
make files.  An individual project's make files can make the transition
from using one hash to another, since it knows how it's been using the
hashes and how to ensure a clean transition when it comes to change the
hash function used.

        Eddy.