Re: [bug #55243] Request for a way to indicate that the same recipe execution produces several targets

[Renaud Pacalet]

On 22/12/2018 02:10, Brian Vandenberg wrote:
> I usually instruct my co-workers to avoid making recipes along those
> lines as I consider it to be a form of painting yourself into a corner,
> though there are times where it's unavoidable.
> 
> In the build I maintain it used to have something like this:
> 
> blah.o : blah.xyz <http://blah.xyz>
>> some command | sed 'some stuff' | some other command > blah.cc
>> ${compiler and flags} blah.cc -o blah.o
> 
> There were a few problems with it:
> 
> * The 1st line of the recipe also produced a header as a side effect
> (hidden dependency)
> * This won't fail the build: /bin/true | /bin/false | /bin/true.  That
> can be changed if bash is the shell your build uses (.SHELL_FLAGS :=
> -euo pipefail -c)
> * Even if one command in that pipeline fails the build it might not be
> obvious what the failure was.
> 
> I changed it to (extensions changed to protect the innocent):
> 
> blah.x1 : blah.xyz <http://blah.xyz>
>> some command > address@hidden
> 
> blah.x2 : blah.x1
>> sed 'some stuff' > address@hidden
> 
> blah.cc : blah.x2
>> some other command > address@hidden
> 
> blah.h : blah.cc
>> no real recipe was provided, just adding this note for emphasis; this
> last part is how I suggest you solve it

Perfect but this does not work in the situations I am interested in,
that is where one single atomic command produces several files. Example:
pdflatex produces several files and there are cases where you want to
track some of them, e.g. document.pdf and document.aux.
-- 
Renaud

> 
> -brian
> 
> On Wed, Dec 19, 2018 at 5:53 AM Renaud Pacalet <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     URL:
>       <https://savannah.gnu.org/bugs/?55243>
> 
>                      Summary: Request for a way to indicate that the
>     same recipe
>     execution produces several targets
>                      Project: make
>                 Submitted by: pacalet
>                 Submitted on: Wed 19 Dec 2018 12:53:09 PM UTC
>                     Severity: 3 - Normal
>                   Item Group: Enhancement
>                       Status: None
>                      Privacy: Public
>                  Assigned to: None
>                  Open/Closed: Open
>              Discussion Lock: Any
>            Component Version: 4.2.1
>             Operating System: Any
>                Fixed Release: None
>                Triage Status: None
> 
>         _______________________________________________________
> 
>     Details:
> 
>     This request for enhancement concerns cases where multiple targets are
>     produced by one single execution of a recipe.
> 
>     I frequently encounter situations where a single recipe execution
>     produces
>     several targets and I'd like make to know about all these targets.
> 
>     I know there is a side-effect of pattern rules with several targets
>     that leads
>     make to consider that all targets matched by one activation of the
>     rule are
>     produced by a single execution of the recipe.
> 
>     But exploiting this sometimes leads to clumsy Makefiles where
>     pattern rules
>     are used without any other reason than this side effect. Moreover,
>     building
>     the list of pattern targets is sometimes difficult.
> 
>     It would be much more convenient to have a new type of rule
>     dedicated to this
>     situation. For instance, a triple-colon rule:
> 
> 
>     a b c::: foo
>         touch a b c
> 
> 
>     Of course, there are several related questions, like, for instance:
> 
>     0 the semantics of the $@ automatic variable (list of targets, first
>     target in
>     the list, other?),
>     0 the existence or not of a corresponding (static) pattern rule,
>     0 ...
> 
> 
> 
> 
>         _______________________________________________________
> 
>     Reply to this item at:
> 
>       <https://savannah.gnu.org/bugs/?55243>
> 
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> 
> 
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> 


-- 
Renaud Pacalet
Télécom ParisTech - LabSoC, c/o EURECOM
Campus SophiaTech,
450 Route des Chappes, CS 50193 - 06904 Biot Sophia Antipolis cedex, FRANCE
Tel : +33 (0) 4 9300 8402
Web : http://www.telecom-paristech.fr/

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