On Thu, Jan 11, 2024 at 02:22:19PM +0100, Alejandro Colomar wrote: > Hi Paul! > > On Thu, Jan 11, 2024 at 01:44:19AM -0500, Paul Smith wrote: > > I've implemented a new capability for conditional assignments (not > > pushed yet). > > > > After these changes, a "?" can precede any type of assignment > > operation, not just "=", and make it conditional (that is, it only > > takes effect if the variable is not already set). > > > > So for example, in addition to "?=" which creates a recursive variable > > if the variable is not set yet, GNU Make will support "?:=" which > > creates a simple variable if the variable is not set yet. > > Thanks!! > > > Of course if > > it's already set then the right-hand side of the assignment is not > > expanded. > > > > Similarly the assignments "?::=" and "?:::=" are also supported. > > > > > > There is one question I wanted to ask for opinions on: what should we > > do with the "?+=" operator? > > There's a use for it: appending to a variable if it wasn't set in the > environment (ignoring what happened in the Makefile). > > Here's what += does: > > alx@debian:~/tmp$ cat Makefile > var ?= foo > var += bar > $(info $(var)) > alx@debian:~/tmp$ make > foo bar > make: *** No targets. Stop. > alx@debian:~/tmp$ make var=foo > foo > make: *** No targets. Stop. > alx@debian:~/tmp$ var=foo make > foo bar > make: *** No targets. Stop.
Sorry for reusing "foo". I'll rewrite with quux, which will be clearer.
alx@debian:~/tmp$ cat Makefile
var ?= foo
var += bar
$(info $(var))
alx@debian:~/tmp$ make
foo bar
make: *** No targets. Stop.
alx@debian:~/tmp$ make var=quux
quux
make: *** No targets. Stop.
alx@debian:~/tmp$ var=quux make
quux bar
make: *** No targets. Stop.
>
> And here's what ?+= could do:
alx@debian:~/tmp$ cat Makefile
var ?= foo
var += bar
$(info $(var))
alx@debian:~/tmp$ make
foo bar
make: *** No targets. Stop.
alx@debian:~/tmp$ make var=quux
quux
make: *** No targets. Stop.
alx@debian:~/tmp$ var=quux make
quux
make: *** No targets. Stop.
> alx@debian:~/tmp$ cat Makefile
> var ?= foo
> var ?+= bar
> $(info $(var))
> alx@debian:~/tmp$ make-9000
> foo bar
> make: *** No targets. Stop.
> alx@debian:~/tmp$ make-9000 var=foo
> foo
> make: *** No targets. Stop.
> alx@debian:~/tmp$ var=foo make-9000
> foo
> make: *** No targets. Stop.
>
> In the last case (environment variable), since var was set, ?+= would do
> nothing, unlike +=.
>
--
<https://www.alejandro-colomar.es/>
Looking for a remote C programming job at the moment.
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