Re: Antwort: Re: Feature request: meta files & wildcards (once again)

[Alexandre Duret-Lutz]

 Bruce> GEN_LIST = foo.h bar.h baz.h
 Bruce> $(GEN_LIST) : gen-stamp
 Bruce> gen-stamp : <predecessor-list>
 Bruce> <generator-command> && touch $@
 
 adl> Yes, it's just the same: you can pick any file in GEN_LIST and
 adl> use it in lieu of gen-stamp.

 bernd> No it's not (I think).
 bernd> 
 bernd> $ cat >Makefile
 bernd> GEN_LIST = foo.h bar.h baz.h
 bernd> 
 bernd> all: foo.h bar.h baz.h
 bernd> 
 bernd> xyzzy:
 bernd>         touch xyzzy
 bernd> 
 bernd> foo.h: xyzzy
 bernd>         touch $(GEN_LIST)
 bernd> ^D
 bernd> $ make
 bernd> touch foo.h bar.h baz.h
 bernd> $ rm -f bar.h  # oops, I edited a generated file
 bernd> $ make
 bernd> make: *** No rule to make target `bar.h', needed by `all'.  Stop.
 bernd> 
 bernd> Is this what you meant?

Almost.  Your Makefile lacks the `bar.h baz.h: foo.h' dependency.

| GEN_STAMP = foo.h
| GEN_OTHERS = bar.h baz.h
| GEN_LIST = $(GEN_STAMP) $(GEN_OTHERS)
| 
| all: $(GEN_LIST)
| 
| xyzzy:
|         touch xyzzy
| 
| $(GEN_STAMP): xyzzy
|         touch $(GEN_LIST)
| 
| $(GEN_OTHERS): $(GEN_STAMP)

What I was saying is that Bruce is just using the same scheme
with an additional file:

 GEN_STAMP = gen-stamp
 GEN_OTHERS = foo.h bar.h baz.h


In both cases, you're right to complain that these rules can't
recover from the deletion of a file in GEN_OTHERS:

~/tmp % make                                                         18:00 #374
touch xyzzy
touch foo.h bar.h baz.h
~/tmp % rm foo.h                                                     18:00 #375
~/tmp % make                                                         18:00 #376
touch foo.h bar.h baz.h
~/tmp % rm bar.h                                                     18:00 #377
~/tmp % make                                                         18:00 #378
make: Nothing to be done for `all'.
~/tmp % make bar.h                                                   18:00 #379
make: Nothing to be done for `bar.h'.
~/tmp % ls -l bar.h                                                  18:00 #380
ls: bar.h: No such file or directory
~/tmp %                                                              Err 1 #381

 bernd> This seems similar to AM_YFLAGS = -d where removing
 bernd> either the parser or its definitions can cause build
 bernd> failures virtually requiring one to re-untar the source
 bernd> to fix them.

There is a solution to this.  It is used in the rule for
config.h, probably it should be used for the Yacc rules too:

| GEN_STAMP = foo.h
| GEN_OTHERS = bar.h baz.h
| GEN_LIST = $(GEN_STAMP) $(GEN_OTHERS)
| 
| all: $(GEN_LIST)
| 
| xyzzy:
|       touch xyzzy
| 
| $(GEN_STAMP): xyzzy
|       touch $(GEN_LIST)
| 
| $(GEN_OTHERS): $(GEN_STAMP)
|       @if test ! -f $@; then \
|         rm -f $(GEN_STAMP); \
|         $(MAKE) $(GEN_STAMP); \
|       else :; fi

~/tmp % make                                                         18:04 #384
touch xyzzy
touch foo.h bar.h baz.h
~/tmp % rm foo.h                                                     18:04 #385
~/tmp % make                                                         18:04 #386
touch foo.h bar.h baz.h
~/tmp % rm bar.h                                                     18:04 #387
~/tmp % make                                                         18:04 #388
make[1]: Entering directory `/home/adl/tmp'
touch foo.h bar.h baz.h
make[1]: Leaving directory `/home/adl/tmp'
~/tmp %                                                              18:04 #389

-- 
Alexandre Duret-Lutz